What to do if chickens have bird flu? The first signs and treatment of bird flu in humans


Birds, like humans, get the flu. Influenza viruses infect birds, including chickens and poultry, as well as wild birds such as ducks.

Most bird flu viruses infect only birds. However, bird flu can be a danger to people. The first human infection with the H5N1 virus occurred in 1997 in Hong Kong. Since then, the bird flu virus has spread among birds in Asia, Africa, the Middle East and Europe.

Avian influenza is a disease caused by strains of the influenza virus that primarily affects birds.

In the late 1990s, a new strain of bird flu emerged that has been shown to cause serious illness and death, especially in poultry such as ducks, chickens or turkeys. As a result, this strain was called highly pathogenic (i.e. very dangerous and infectious) by bird flu and got the term H5N1.

In total there are 16 different types of bird flu. Strain H5N1 is a matter of great concern, as it is the most contagious and deadliest. Fortunately, it’s very difficult for people to get this virus.

A relatively new strain of bird flu has been discovered in China. Influenza A virus has been named H7N9 (H7N9 Chinese Avian Influenza). On March 31, 2013, H7N9 virus identification was reported; the new strain was different in antigenic composition from the H5N1 avian influenza virus. Unfortunately, the H7N9 bird flu strain seems to be genetically unstable.

Since its discovery in 2013, at least 48 different subtypes of H7N9 have been identified. Since some H7N9 viruses persist on chicken farms in China, researchers fear that their strains will continue to exchange genes with other influenza viruses, which could lead to a new pandemic.

Since the detection of highly pathogenic influenza, infected birds have been found in Asia, Europe, Africa and the Middle East. Careful control measures, including the eradication of infected flocks of birds and vaccination of healthy animals, have reduced the number of cases, but the virus continues to exist among domestic birds in the regions of Asia and Africa. In 2007-2008, there was a small outbreak in Bangladesh and Pakistan associated with the infection of domestic chickens.

In March 2015, bird flu was discovered in the United States in several herds of turkeys. This has led several countries to ban the import of American poultry products.

Similarly, in March 2015 in the Netherlands, bird flu was discovered in chickens. Most experts believe that poultry is infected with bird flu due to fecal contamination of wild birds.

As of March 2015, no human cases of bird flu have been detected in the US population. Although the swine flu virus H1N1 that caused the pandemic contains some bird flu genes, it was not the original H5N1 virus.

The virus spreads among birds due to the fact that infected birds secrete it in their saliva, nasal secretion and droppings. Healthy birds become infected when they come into contact with infected secrets or droppings of sick animals.

Contact with infected surfaces (such as a cage) can also allow the virus to spread from bird to bird. Symptoms in birds can range from not severe (for example, a decrease in the number of eggs) to the development of several important organ failure and death.

First human case of the disease, developed from infection with highly pathogenic avian influenza, was discovered in 1997. From then until 2016, according to the World Health Organization, 846 people were infected with the H5N1 virus, of which 449 people died.

Human cases of highly pathogenic avian influenza have been most commonly observed in Southeast Asia and Africa. Mutations often occurred in the virus, and it is possible that some of them could create a more contagious virus that could cause a regional epidemic or a worldwide bird flu pandemic in humans.

Fortunately, the mutations that have occurred so far have not made the virus more contagious, although concerns remain. Anxiety is the discovery of a strain of bird flu H7N9.

Four people in China were infected with the H7N9 virus, two of them died. Health officials around the world are concerned about the possibility of a bird flu that could easily spread from birds to humans. Although light transmission between people has not yet developed, H7N9 bird flu has infected 707 people, of which 277 have died. Most of these infections have been associated with contact with infected birds or their droppings.

Table. Number of confirmed cases of avian influenza A H5N1, according to the World Health Organization, 2003-2015

A country Total cases Is dead
Azerbaijan 8 5
Bangladesh 8 1
Cambodia 56 37
Canada 1 1
China 53 31
Djibouti 1
Egypt 346 116
Indonesia 199 167
Iraq 3 2
Lao People's Democratic Republic 2 2
Myanmar 1
Nigeria 1 1
Pakistan 3 1
Thailand 25 17
Turkey 12 4
Vietnam 127 64
TOTAL 846 449

What is the cause of bird flu?

Avian influenza is caused by strains of the influenza virus that have evolved in a way that specifically adapts to penetration into bird cells.

There are three main types of flu:

The bird flu virus is influenza A, which contains eight strands of RNA that make up its genome.

Influenza viruses are classified based on the analysis of two proteins on their surface - hemagglutinin (H) and neuraminidase (N). There are many types of hemagglutinin and neuraminidase proteins.

For example, a recent pathogenic avian influenza virus had type 5 hemagglutinin and type 1 neuraminidase. Thus, it was called the “H5N1" influenza A virus.

The 2013 virus had other surface proteins, H7 and N9, hence the name H7N9. Other types of bird flu include H7N7, H5N8, H5N2 and H9N2.

There are many types of influenza viruses, most of them prefer to live in a limited number of animals. Thus, swine flu predominantly infects pigs, and bird flu infects birds. Human flu strains are best adapted to humans.

A small number of infections can occur in a random host, for example, when people come into close contact with infected birds and become infected with bird flu. In addition to humans and birds, it is known that bird flu viruses can sometimes infect pigs, tigers, leopards, ferrets, domestic cats and dogs.

Influenza viruses mutate frequently and easily. These mutations can occur spontaneously in a single virus or can occur when two different strains exchange genetic material. Influenza viruses have two main types of mutations:

  • antigenic shift, when large segments of RNA are interchanged between different types of influenza viruses;
  • antigenic drift when small RNA sequences are interchanged.

As a rule, antigenic shift is responsible for the emergence of new strains.

For example, in 2009, the swine flu pandemic was caused by a virus that included genetic material from strains of swine, bird and human flu. New mutations can allow the virus to evade the immune system and make old vaccines ineffective.

In 2011, one strain of a highly pathogenic avian influenza virus mutated in this way, making the existing vaccine that was used against bird flu ineffective against the new strain. Sometimes the flu virus mutates in such a way that it becomes able to infect new species of animals.

Serious flu pandemics occur when a relatively new strain of influenza virus appears that is highly contagious to humans. The most deadly pandemic in modern history was the 1918 flu (also known as the Spanish flu, although it did not occur in Spain).

The 1918 virus quickly spread and killed tens of millions of people around the world. Mortality was particularly high among young healthy adults. Although the 1918 virus was a human influenza virus, it possessed many genes that probably came from a strain of bird flu. One of the reasons why the health authorities are closely monitoring and trying to limit the contact of people with sick birds is associated with an attempt to reduce the chances of the emergence of new strains that may have the ability to develop well in human tissues.

What are the risk factors for bird flu?

People can get bird flu through contact with infected birds (like chickens) or their infected droppings or secretions.

Risk factors include caring for sick birds, killing sick birds, and preparing them for consumption. Despite the huge number of people who come in contact with birds every day around the world, human cases of bird flu remain rare.

This highlights how difficult it is for bird flu to infect human cells, but these difficulties can reduce mutations such as antigenic shift. The H1N1 swine flu pandemic that began in Mexico is an example of such a mutation.

Although direct exposure to sick birds poses the highest risk of developing bird flu, indirect exposure to bird droppings or other foods (such as eggs) is also dangerous. Contact with unwashed eggs from sick birds or water contaminated with their droppings is a potential risk of developing the disease.

Human-to-human transmission of the virus has occurred in isolated cases. Therefore, caring for a person infected with bird flu is also a risk factor for the development of the disease.

There is a theoretical risk for laboratory staff who work with bird flu viruses. In 2009, there was one case where a company inadvertently sent live bird flu samples to a research laboratory, which were then used to vaccinate ferrets. This infected vaccine did not lead to the development of human diseases.

Is it possible to get infected from another person?

Sometimes - after personal contact - a patient with bird flu can infect another person.

In 2006, 8 members of the same family fell ill with bird flu in Indonesia, seven of them died. Why this happened is not exactly known. Family members are likely to come in contact with infected birds. They could also have common genes that made them particularly susceptible to the virus.

What about the genetically modified in vitro bird flu?

In the fall of 2011, Dutch scientists made a stunning statement. They genetically altered the H5N1 virus so that it spreads among the ferrets by airborne droplets.

Why were ferrets chosen? Almost all human influenza viruses spread easily among these animals, which is why they are often used in scientific research.

Scientists in the United States also created a mutant strain of H5N1 that spread among mammals.

These studies have shown that the H5N1 virus has great potential for obtaining dangerous transmission ability among mammals, including humans.

Scientists have not released important information on the creation of mutant viruses; These parts are only available to qualified researchers.

But these studies have caused very pronounced controversy. Some scientists say that mutant viruses cannot be created, as they can go beyond laboratories. In 1977, the H1N1 flu, which was considered missing, broke out on the border between Russia and China. Although authorities have denied this, many scientists believe the virus has spread from the lab.

What are the symptoms and signs of bird flu?

Symptoms occur approximately 2-8 days after infection. Infected people suffer from common flu symptoms, which may include:

  • Temperature rise (above 38 ° C).
  • Cough (usually dry, without sputum production).
  • A sore throat.
  • Muscle pains.
  • Nausea.
  • Vomiting
  • Diarrhea.
  • Headache.
  • Joint pain.
  • Lethargy.
  • Discharge from the nose (runny nose).
  • Insomnia.
  • Eye infections.

In children, the symptoms are similar. This viral infection can progress to pneumonia and respiratory failure. Avian influenza causes a very aggressive form of pneumonia (acute respiratory distress syndrome or ARDS), which is often fatal.

How do doctors diagnose bird flu?

Conventional human influenza A tests will be positive in patients with bird flu, but they are non-specific. To establish an accurate diagnosis of bird flu, you need to conduct specialized tests. The virus can be detected in sputum using several methods, including cultivation in cell cultures or polymerase chain reaction (PCR). The cultivation of the virus in cell culture is carried out in laboratories with appropriate biosafety certification. PCR detects the nucleic acid of the influenza A virus. Specialized PCR detects avian strains.

During and after infection with bird flu, the body produces antibodies against the virus. Blood tests can detect these antibodies, but this requires one blood sampling at the onset of the disease, and the second in a few weeks. Therefore, the results are usually available already when the patient has recovered or died.

How to treat bird flu?

Due to the small number of human cases, scientific research on the treatment of bird flu has failed.

It is believed that the best way to prevent the development of bird flu is to avoid contact with sick birds and their droppings. People are advised not to touch any sick or dead bird. The World Health Organization currently recommends oseltamivir (Tamiflu) and zanamivir (Relenza) for the treatment and prevention of bird flu. These drugs can suppress virus replication and improve patient outcomes, especially survival rates.

For a better effect, Tamiflu should be taken within 48 hours after the onset of symptoms. But, since the death rate from bird flu is very high, doctors should prescribe oseltamivir to those patients who were later diagnosed.

For patients in serious condition, doctors can increase the recommended daily dose or extend treatment. It must be borne in mind that the absorption of the drug can be severely impaired in patients with severe gastrointestinal symptoms.

Patients with suspected or suspected bird flu should stay at home or be hospitalized (isolated from other people).

Although Tamiflu and Relenca can be effective in treating the flu caused by the H5N1 avian influenza virus. However, more research is needed to demonstrate their effectiveness.

Scientists from the USA and China have reported cases of drug resistance of human H5N1 viruses.

Patients should:

  • relax;
  • drink plenty of fluids;
  • to eat well;
  • take drugs for pain and fever (prescribed by your doctor).

H5N1 infected patients often develop complications, such as bacterial pneumonia. They need antibiotics, and some need extra oxygen.

What are the complications of bird flu?

Bird flu complications include:

  • shortness of breath
  • pneumonia
  • acute respiratory distress syndrome (ARDS);
  • lung collapse;
  • mental disorders;
  • cramps
  • insufficiency of organs and systems;
  • death.

Unfortunately, patients infected with bird flu often have one or more of the complications listed above. Mortality rates for the H5N1 strain are approximately 55%, and for the H7N9 strain, approximately 37%.

What is the prognosis for bird flu?

In human cases of bird flu, the prognosis remains poor. Many cases of the disease developed in poor people living in rural areas of underdeveloped countries who did not have access to modern intensive care units or antiviral therapy.

Approximately 55% of people diagnosed with H5N1 bird flu died from the disease; H7N9 strain has similar mortality rates of 37%. Surviving people can have long-term health problems if organs and their systems are severely damaged.

Avian Influenza Prevention

It is currently impossible to stop the spread of bird flu - it is a virus that is carried by birds, including wild birds that migrate. Understanding bird migration and monitoring their movements provides health and agricultural authorities with the necessary data to protect people and pets.

Vaccination  - There is a vaccine against human seasonal flu, but not bird flu. Various laboratories around the world, as well as pharmaceutical companies, are working on a bird flu shot.

In 2007, the first vaccine for people against the highly pathogenic avian influenza virus was approved in the United States. This vaccine was made from inactivated viruses and did not contain live.

It stimulates the immune system to produce antibodies against bird flu, which, presumably, can protect a person from this disease. The vaccine was purchased by the US government and included in the strategic national stock. It has not become accessible to ordinary people, as the United States currently does not have problems with the highly pathogenic avian influenza virus.

Side effects of the vaccine include arm pain, fatigue, temporary muscle pain. The vaccine has not been tested on a large number of people, so there may be other, not yet discovered, side effects. This vaccine is effective against a strain that caused large outbreaks of bird flu, but it does not work against a newly mutated strain discovered in 2011. It is unlikely to provide protection against the new H7N9 bird flu.

Research on influenza vaccines is ongoing. New developments against relatively constant influenza virus antigens may lead to a vaccine that protects against most (if not all) influenza viruses. If these studies are successful, potential outbreaks of the flu, including bird flu, can be reduced or prevented in the future.

Everyone can minimize the spread of influenza, bird flu, and many other infections:

  • Hand hygiene - you need to regularly wash your hands with warm water and soap, before and after going to the toilet, before cooking. It is necessary to wash hands after coughing.
  • When coughing, you need to cover the inside of the elbow, and not with a brush. When coughing into a brush and then touching some things, the virus can remain on their surface and other people can become infected. If possible, it is best to use tissue when coughing, which you must then carefully discard.
  • Patients need to stay away from public places and avoid contact with people.
  • When visiting a doctor, the patient must immediately say in the admission department that he needs to be isolated from other people. In some institutions, the patient may be given a surgical mask.
  • It is necessary to adhere to the recommendations regarding vaccination against seasonal flu and pneumococcal infection.

When cooking, you cannot use the same dishes for raw and cooked meat. Before touching a raw bird, you need to wash your hands with soap and water. This must be done after that.

Cooked poultry is safe to eat.

Do not come close to dead or sick birds.

What are the experts afraid of?

Currently, it is very difficult for a person to become infected with bird flu; even less often, one person transfers this disease to another. Experts fear that if a person already sick with seasonal flu gets the bird flu, the H5N1 virus might exchange genetic information with the human H1N1 flu virus and gain its ability to spread from person to person. An easily transmitted bird flu virus between people can have dire consequences.

Avian influenza has a very high mortality rate, and if it causes a pandemic, millions of people may die.

In order to infect a person, the H5N1 strain must penetrate deep into the lungs. This feature makes it more deadly, but also less contagious. People with an infection located deep in the lungs produce less virus with coughing and sneezing, compared with patients with an upper respiratory tract infection.

A mutated virus can, for example, infect the upper respiratory tract, as well as the deep. Sick people will then secrete more viruses with coughing and sneezing, which will make it easier to infect others. Nearby people become infected more easily, since the virus will not need to penetrate deep into the lungs to cause the disease.

Controlling bird flu outbreaks helps reduce the likelihood that the bird flu virus will come into contact with the human flu virus and mutate. It is also important to monitor seasonal human flu. The World Health Organization says that the rapid elimination of outbreaks of bird flu is a top priority for public and global health.

We try to provide the most relevant and useful information for you and your health. The materials on this page are for informational purposes and are intended for educational purposes. Website visitors should not use them as medical recommendations. Determining the diagnosis and the choice of treatment methods remains the exclusive prerogative of your doctor! We are not responsible for any negative consequences arising from the use of information posted on the website

Academician of RAMS O. KISELEV, Director of the Research Institute of Influenza RAMS (St. Petersburg).

Recently, they have been talking and writing a lot about bird flu. A dangerous virus roams the planet. Reports of new foci of disease among birds come either from Turkey, then from Romania, or from the south of Russia ... Even people far from medical science, before the threat of an influenza pandemic, became interested in epidemiology, virology and immunology.

Oleg Ivanovich Kiselev.

H5N1 avian influenza virus (shown in yellow), growing in cell culture. Recently, it is this virus that causes outbreaks of the incidence of influenza among migratory and poultry.

Schematic representation of type A influenza virus. The genome of the virus consists of eight RNA segments. Influenza A virus subtypes differ in hemagglutinin HA variants (16 variants) and NA neuraminidase (9 variants).

Classification of type A influenza viruses according to two surface antigens (HA hemagglutinin and neuraminidase A) and animal and bird species - intermediate and final hosts of these types of viruses on the route of infection transmission to humans.

Field hospital for patients with influenza. USA, 1918.

The spread of bird flu, according to WHO, as of October 2005. The red color indicates the areas where outbreaks of the disease were observed among poultry.

Disinfection of the train that followed the areas where quarantine was introduced due to bird flu. Bucharest, 2005.

The magazine has already written about the classification and structure of influenza viruses, about the characteristics of bird flu and its distribution, about the causes of pandemics in humans. (See the article of the Corresponding Member of the Russian Academy of Medical Sciences N. Kaverin, “Changeable Influenza,” “Science and Life” No.) Readers of the journal, in their letters to the editor and questions sent to the site “Science and Life,” ask to explain the reasons for the appearance of the new virus, why bird flu has become widespread and how dangerous are bird epidemics for humans. The director of the St. Petersburg Institute of Influenza RAMS, academician of the RAMS Oleg Ivanovich Kiselev, answers these and other questions of concern to many. The conversation is led by the candidate of chemical sciences O. Belokoneva, head of the department of medicine of the journal Science and Life.

Academician of RAMS O. KISELEV, Director of the Research Institute of Influenza RAMS (St. Petersburg). - Recently, outbreaks of flu among birds have become widespread. Have such epidemics ever happened before?

Birds became carriers of influenza viruses millions of years ago. We can say that they are a reservoir of all influenza viruses of subtype A that exist in nature. They have no subtype B virus. Avian "reservoir" has developed genetically as a result of evolution.

Bird flu viruses were isolated in the 30s of the last century, their evolution is seriously studied by experts in environmental virology in our country and abroad. Doctors know the genealogy of these viruses, their genome, properties. Large collections of non-pathogenic, non-hazardous to humans, avian viruses have been compiled. The “normal” bird flu virus is not transmitted from bird to person and from person to person. But from time to time the "reservoir" gives out options that are dangerous to people. By the way, a study of the origin of animal and human influenza viruses has shown that they all have one evolutionary source - avian influenza viruses.

What should happen to the bird flu virus to become pathogenic for humans? What are the mechanisms of the "transformation" of the bird flu virus into the "human"?

The traditional viral chain begins with wild waterfowl. It was found that they are carriers of all 16 subtypes of influenza A viruses, and the most primitive combinations of surface antigens (hemagglutinin HA and neuraminidase NA. - Note ed.) these viruses have up to 254. Every year, migratory birds generate various variations of the influenza A virus in their bodies. And this is at a body temperature of 42.5 ° C. That is, the bird flu virus survives under conditions in which a person is already in a half-fainting state.

Staying in ponds with stagnant water, the migratory bird introduces a virus with feces that can live up to 400 days - naturally, at optimal temperatures - from 10-12 to 30 ° C. The virus is transmitted through water to waterfowl, and from it to other domestic birds. feathered. Turkeys and chickens are most susceptible to infection. Further, the flu virus can go to pigs, which already poses a threat to humans. The fact is that on the surface of the membrane of pig cells there are two types of receptors to which the influenza virus is able to attach: one is the bird variant, and the other is the human one. And exactly half and half. Therefore, a pig can become an intermediate host of both avian and human influenza viruses. When two viruses - human and avian - infect the same cells, the offspring of these viruses inherits sets of RNA segments of both viruses. And as a result of their interpenetration (reassortment), sometimes a third highly pathogenic virus individual is born that is able to overcome interspecific barriers and be transmitted to humans and birds. It is no coincidence, according to statistics, the number of deaths from influenza is large if a person becomes infected in rural areas.

In addition, constant mutations of genes occur in the avian influenza virus itself, which determine the so-called host range. These are the hemagglutinin (HA) genes that control the entry of the virus into the host cell, and the internal genes of the virus that are directly responsible for suppressing the host's immunity. As a result of these mutations, a virus that is dangerous to humans can also appear.

-  Why are almost all cases of human cases of bird flu reported in Southeast Asia?

In Southeast Asia, a high population density is combined with intensive livestock and poultry farming. These are very suitable conditions for the variability of influenza viruses. As a result, the bird flu virus began to overcome interspecific barriers - they began to hurt both animals and people. Interestingly, in the Central Asian region, where there is an intensive exchange of influenza viruses between wild migratory birds and domestic animals, but due to cultural and religious traditions, there is no pig farming, and the likelihood of pandemic viruses is much lower than, for example, in China.

Influenza viruses that caused pandemics of the twentieth century (in 1918, 1957, 1968), were of bird origin or, nevertheless, human?

All pandemic viruses of the twentieth century to one degree or another contained segments of bird flu RNA. We can say that they had a bird’s footprint.

Over the past two years, about 140 cases of human infection with the H5N1 avian influenza virus have been reported in the world, half of them are fatal. Is the H5N1 avian influenza virus purely avian or already partially human?

This is a purely bird virus, but it is constantly changing, more and more adapting to the human body. And yet, I think this virus will not cause a flu pandemic among people. To become pandemic, it must undergo major changes - reassortment or additional mutations. After all, as I already said, in all pandemic viruses of the twentieth century there were both avian and human RNA segments.

It is widely believed that the threat of bird flu is an artificially inflated "horror story" that benefits large multinational poultry and pharmaceutical companies. How can you comment on this?

The 2004-2005 sample H5N1 virus has indeed undergone changes and has become more dangerous than before. This is evidenced by such a large number of dead poultry. As a result, the risk of human disease increases. In 1997, the first outbreak of an epidemic among birds in Hong Kong was localized due to the fact that all livestock of poultry in the country was destroyed. Now it is impossible to do this - the virus has spread throughout Asia. And the simultaneous outbreaks of bird flu in Japan, China, Vietnam, Thailand, Russia, Kazakhstan are historically unprecedented. There is concern that a new strain of the bird flu virus could hit the whole world.

While the virus is not transmitted from person to person, but because of the epidemic among birds, such transmission is becoming more likely. What is needed is just the “right” recombination between the H5N1 strain and the human influenza virus. This can happen if one of the people or animals gets sick with human and bird flu at the same time. As soon as the bird virus acquires the ability to spread from person to person, a pandemic can begin, since in the human population, immunity against bird viruses is low or completely absent. Recent studies show that the Spaniard in 1918 claimed more than 40 million lives because the influenza virus evolved from a bird and contained unique antigen proteins (HA and NA) to which the person was not immune. In addition, it has been reliably established that a number of internal proteins of the Spanish virus, also of bird origin, had an outstanding ability to suppress human immunity.

The bird flu virus can persist for many years at temperatures below _70 ° C. Therefore, the risk of the virus remaining in chilled and frozen poultry meat is increased. But, fortunately, there can be no infectious virus in fried chicken meat or after cooking. It is interesting that the virus categorically does not withstand the procedures of sequential freezing and thawing.

What happened in the fall of 2005 in the Russian regions, when the death of the bird population became epidemic, made our scientists sound the alarm. So the threat of a surge in the incidence of bird flu among people is a reality, not a horror story invented by someone.

If the H5N1 virus is not likely to become pandemic, then why are all bird flu vaccines now based on it?

All countries are required to have this vaccine as a backup, in case of the massive spread of this particular type of bird flu. And when a new virus appears, then there will be a new vaccine. In the flu-like problem it always happens. Every year we analyze the situation and offer new vaccine compositions. Vaccine strains change on average after two to three years. Maybe in one or two years a new candidate will appear on the basis of another strain of bird flu virus.

-  The flu research institute has developed a new vaccine for bird flu. Tell about her.

In fact, the vaccine was developed as part of the World Health Organization. Today it is impossible to quickly solve the problem of creating a vaccine without cooperating with foreign scientists without a healthy corporate spirit. The main base strain H5N1 obtained from the National Institute of Biological Standards and Control John Wood in London. This work was published in Nature in the middle of last year. Last summer, we studied the virus as a candidate for vaccine strains. And in August, at a meeting with the chief sanitary officer of Russia, they came to the conclusion that it was necessary to prepare a vaccine based on this strain and put it into production. Similar vaccines are being developed in other countries. So, the Americans have already launched a bird flu vaccine into production. Now they are preparing to produce a new vaccine from the Indonesian isolate. And in Russia, due to the fault of manufacturers, the timing of the release of the bird flu vaccine has not yet been determined.

And why is it impossible to construct a universal vaccine against all possible combinations of influenza virus antigens?

There are already several universal flu vaccine projects in the world. In terms of complexity, such a project is comparable, if not with a flight to Mars, then with something close to this. And our institute is also working on this issue, with virtually no funding. I think that if we have the money, we can make such a basic vaccine.

-  Is it theoretically possible to make the human body invulnerable to influenza viruses?

It is quite possible to protect the human body from the influenza virus at the genetic level. But everyone knows that genetic manipulations of any kind on the human genome are strictly prohibited. And with respect to birds and animals, the likelihood of such an approach exists. So, for example, American geneticists propose introducing genes encoding protein structures that neutralize antigenic molecules of the influenza virus (the so-called antisense structures) into the DNA of a bird. In the presence of such proteins, the bird flu virus will not be able to attach to the host cells. As a geneticist in basic education, I can say that it is likely that humanity will have to follow the path of genetic modification, ensuring the safety of agricultural and wild animals.

-  How can you protect yourself from the flu, including bird flu, without vaccination?

For the prevention and treatment of influenza, including avian origin, the Research Institute of Influenza recommends domestic preparations that are part of the kit: "Interferon gamma human recombinant" ("Ingaron") and "Interferon alpha-2b human recombinant" ("Alpharona"). The medicine is simply instilled into the nose. The kit can be purchased at the pharmacy without a prescription. I would especially like to emphasize that these drugs, created by Moscow scientists in conjunction with the St. Petersburg Research Institute of Influenza RAMS, exhibit high therapeutic activity on the model of bird flu. Only timely prophylaxis of influenza can prevent the development of a severe course of the disease with an unpredictable outcome.

-  How likely is a person to die if he does get the bird flu?

Despite the danger of the virus, death from any influenza infection is an extraordinary event. First of all, you should consult a doctor on time and properly treat the infection. The likelihood of death from avian influenza largely depends on the patient’s health and on the organization of the country's healthcare system. According to experts of the research institute of influenza, death from influenza in our time is an extraordinary event.

-  Will poultry be vaccinated against bird flu?

The All-Russian Institute of Veterinary Poultry in St. Petersburg has developed, successfully tested and has now transferred to the Rosselkhoznadzor for industrial production a highly effective vaccine for birds against the pathogenic H5N1 influenza virus. The studies were conducted jointly with the Research Institute of Influenza, and the entire project was carried out exclusively on enthusiasm without funding from the state budget. This vaccine is just awaiting registration.

-  Birds have many diseases. How to determine that chickens or ducks die from the flu?

Indeed, birds and without flu have many dangerous diseases. For the diagnosis of influenza in birds, WHO recommends immunofluorescence and PCR methods. In our country, bird flu is diagnosed using immunological tests and the determination of pathogenicity in chickens. But these analysis methods take up to two weeks, in addition, they have low sensitivity and specificity. Now our employees with colleagues from the M. M. Shemyakin Institute of Bioorganic Chemistry and Yu. A. Ovchinnikov of the Russian Academy of Sciences in Moscow are developing a chip for the rapid diagnosis of bird flu in birds. Moscow colleagues synthesized the receptors of the avian and human viruses, and here, in the influenza research institute in St. Petersburg, specialists create the biochip itself, which looks like a small plate resembling a credit card with mounted receptors for both types of virus. With the help of such a device, any veterinarian in the district center, having at hand the biomaterial of the dead bird, will be able to understand whether the bird flu virus has infected the bird or is it another infection. A quick diagnosis is essential - the disease is insidious and fleeting.

Is there any data on the species composition of avian flu transmitting birds? Is it possible to get infected from birds during spring hunting?

Among wild migratory waterfowl, the carriers of influenza viruses are wild ducks and geese, terns and plovers. But mostly bird flu viruses were isolated from wild ducks and geese. Hollows, snipe, woodcocks do not get sick. Capercaillie, black grouse, hazel grouse - too. I think the probability of infection from birds in central Russia is small. Most birds do not belong to the carriers of the influenza virus; therefore, they should not be feared, much less destroyed.

-  Why are there no bird flu reports in the US?

There were several outbreaks of bird flu at US poultry farms. However, in this country, the main producers of poultry meat are small factories with thirty to fifty thousand heads. We have bird complexes - this is the millionth number of birds. If on a farm in the USA, for example, ten to twenty thousand individuals die, such a farm is isolated, preventive measures are taken, insurance is paid to the owners. And there is no national tragedy, and the resonance in society is minimal. Given the scale of Russian poultry farms, the level of bankruptcy they suffer is monstrous. Such an out-of-the-ordinary event, of course, will not be ignored either by the sanitary inspection authorities or the press.

Rumor has it that bird flu is the latest biological weapon in the United States, directed against Russia, China and the Asian region. What do you think of it?

When the human immunodeficiency virus was discovered, the Pravda newspaper published a rather large article about the fact that HIV was synthesized in Pentagon laboratories. I declare with all responsibility: humanity has not yet matured to create such "genetic machines". Strengthen the pathogenic properties of the virus, preserve them and make a bacteriological weapon out of the finished virus - yes, you can. But scientists cannot yet pick up a peddler of a virus, for example, a duck: the virus will take root in it or not - this is from the evil one.

In fact, the question is correct. In the future there may be "wise men" who will seriously engage in this kind of "work". But for now, I am sure this is completely ruled out. By the way, scientists are hard to fool: if something artificial appears, then specialists, having clear ideas about the evolutionary development of viruses, will recognize a man-made infection immediately.

Influenza is a whole group of viral diseases. It is divided into three types: A, B and C. The first includes those that affect both people and animals. The respiratory and digestive organs are affected. Bird flu also belongs to it.

The viruses of the second type are dangerous only for humans, and the third - for humans and partly pigs.

It was first discovered in China, in Hong Kong. This happened in 1997. Then the disease spread to Asia, and from there - to Europe and Africa. It is carried mostly with wild migratory birds. They themselves do not get sick at all or carry the flu in a mild form, but they can infect poultry and, less commonly, people.

Avian influenza in Russia

In general, the occurrence of the disease was observed in wild birds. But they were sick and home, especially in the following areas:

  • Novosibirsk;
  • Chelyabinsk;
  • Omsk;
  • Kurgan;
  • Tula;
  • Tyumen;
  • as well as in Altai;
  • and in Kalmykia.

The first cases were recorded in Siberia in 2006. In humans, no bird flu infection has been reported. However, there were epidemics caused by pork and “human” subtypes.

As one of the preventive measures, the ban on the import of poultry carcasses from those countries where outbreaks of this disease were observed is applied. Checks and extermination of infected birds are also carried out.

Avian influenza near Moscow

Cases of infection with this virus are noted near Moscow. In particular, the disease was found in the poultry farms of Schelkovo and Sergiev Posad, as well as in the private courtyards of Mozhaisk and Orekhovo-Zuevsky districts. Infected birds were destroyed. Many poultry farms have quarantined.

Disease characteristics

We will tell you more about it.

The flu is officially called Influenza virus A. It belongs to the family Orthomyxoviridae.

Various subtypes are distinguished, distinguished by structural features of hemagglutinin (which is indicated by the Latin letter H) and neuraminidase (Latin N). The most common strain (subtype) of bird flu is referred to as A / H5N1.

The disease is quite dangerous. According to official figures, more than half of those who died (more precisely, 60%) died. However, it is likely that not all patients went to the doctor. In this case, the probability of dying is less, but still remains quite serious.

Infection

The virus is transmitted from one bird to another. in direct contact. Households can become infected by both the wild and other already infected domestic ones. Dead birds are also contagious.

It is also possible to become infected through:

  • water
  • feed;
  • litter;
  • eggs
  • poultry meat;
  • rodents visiting a chicken coop.

The period from the virus entering the body before the onset of the disease is from 2 to 5 days. This period depends on the state of health, age and the specific strain.

First signs and symptoms

Symptoms are the same as in other types of flu:

  • decreased appetite;
  • sneezing
  • lacrimation
  • disturbances and disheveled plumage;
  • decrease in the number of eggs laid;
  •   with them;
  • respiratory failure;
  • blue and swollen crest;
  • uncoordination of movements;
  • diarrhea.

Photo symptoms in birds:

In humans, bird flu manifests itself:

  • cough and sore throat;
  • fever;
  • muscle and joint pain;
  • etc.

Often pneumonia or other complications develop. This is due to the fact that human immunity is not ready to deal with such varieties. Therefore, as a rule, the disease is more complicated than with types traditional for humans.

How to treat and is it possible to cure?

Unfortunately, there are no ways to treat diseased birds. All sick hens, as well as those who were in contact with them, are destroyed.

Quarantine is the primary means of preventing bird flu in chickens. That is why during outbreaks of flu in other countries, the import of chicken from them is prohibited.

An effective treatment does not exist. Therefore, it is important to adhere to the rules.

  • observe quarantine if a disease is reported in the region;
  • do not buy chickens and eggs from dubious sources;
  • avoid contact with wild birds, especially waterfowl.

Prevention

To prevent infection, it is important:

  • Thoroughly wash knives, boards, etc. with meat cleansers for cutting meat.
  • Keep raw meat out of contact with other foods.
  • Cook (do not eat them raw).
  • Do not touch fluff, feathers, carcasses of infected chickens.
  • Wash hands and chopping tools after contact with raw meat.

Reminder to the population

Regional veterinary services, as well as the Rosselkhoznadzor, issue leaflets. They contain information:

  • bird flu virus;
  • symptoms of the disease;
  • foci of distribution;
  • preventive measures;
  • and other useful information.

What else do you need to do for prevention?

It is also important to do the following:

  • Keep chickens clean, regularly clean and.
  • Limit space.
  • When buying a bird, check veterinary certificates.

Rosselkhoznadzor position

This organization checks households for bird flu. When it is detected, quarantine is declared, and the infected bird is destroyed.

Human impact

For humans, this disease is quite dangerous, because the body rarely encounters such strains. The disease often proceeds with complications, in particular, of the respiratory and cardiovascular system.

People may become infected:

  • in contact with infected chickens;
  • or their meat, eggs, feathers and down;
  • when drinking contaminated water;
  • on contact with droppings.

Under the influence of high temperature (up to 70 ° C), the virus dies. But we do not recommend eating meat and eggs, which are reliably known that they were obtained from birds infected with influenza.

Bird flu- (Grippus avium; highly pathogenic avian influenza, classical bird plague, chicken flu A, exudative typhus, Dutch plague of chickens) - a highly contagious, acute viral infection affecting agricultural, synanthropic and wild birds with respiratory and gastrointestinal tract infections. Bird flu is able to occur in the form of epizootics, causing massive coverage of the livestock and having a wide distribution — district, region, country.

Causative agent of the disease - The RNA-containing virus belongs to the family of orthomyxoviruses, which is divided into three serological types: A, B and C. Type A viruses cause disease in animals and humans. For birds, the most pathogenic viruses of the H5 and H7 subtypes, having the molecular biological characteristics of highly pathogenic viruses. Of greatest concern is the H5N1 virus due to its possible danger to humans. In birds, the virus induces the production of virus-neutralizing and complement-binding antibodies. The stability of the virus in the environment varies depending on the serotype. The virus is sensitive to ether, chloroform, heat and acidic environment (pH 3.0). At a temperature of 55 ° C, it is inactivated for one hour, at 60 ° C in 10 minutes, at 65-70 ° C in 2-5 minutes. With deep freezing (temperature -70 ° C) in meat, the virus remains virulent for more than 300 days. Drying the substrate containing the virus preserves it. Common disinfectants: bleach, sodium hydroxide, phenol, hydrochloric acid, carbolic acid and others quickly inactivate the virus.

Epizootology . Influenza is recorded in many species of domestic and wild birds. The pathogenicity of the virus is not limited only to the type of bird from which it is isolated. In industrial-type farms, the introduction of the pathogen with feed, equipment, and inventory plays a role in the emergence of the disease, while non-sanitized meat and egg containers are of particular danger. All susceptible poultry on the farm usually have the flu for 30–40 days. This is due to the high contagiousness of the virus and the high concentration of poultry in the houses. The source of the causative agent of the infection is a sick bird (within 2 months). The influenza virus causes disease in birds with respiratory, oral, intraperitoneal, subcutaneous and intramuscular infections. In industrial enterprises with the poultry cell system, the aerogenous pathway, as well as the alimentary (transmission with drinking water), is of primary importance in the distribution of the pathogen. From the body of a sick bird, the virus is excreted with excrement, secretion, droppings, and hatching eggs. Rodents, cats, and especially free-living wild birds that enter or nest in houses can take part in the spread of the influenza virus inside the poultry farm. The presence of virus-carrying chickens maintains an epizootic focus on the farm during the reproduction of a new population of susceptible poultry, which, during rearing, becomes ill and supports inpatient distress. Poultry morbidity varies from 80 to 100%, mortality from 10 to 90%, depending on the virulence of the virus and the conditions of the bird.

Pathogenesis. Depending on the virulence, tropism of the virus, the natural resistance of the bird, a generalized or respiratory form of the disease develops. As a result of the virus entering the mucous membranes of the respiratory tract, it begins to multiply actively and penetrates the circulatory system. All this happens within 4-12 hours. The virus is found in large quantities in the blood serum, as well as in red blood cells. In the development of the disease, it is customary to distinguish four phases: active reproduction of the virus and its accumulation in parenchymal organs, viremia - the virus in this phase can be detected in the blood, then the process of antibody synthesis begins, which indicates the cessation of further reproduction of the virus. The last stage is accompanied by the active formation of antibodies and the formation of immunity in the bird.

Clinical picture . The incubation period is 3-5 days. Influenza can occur acutely, subacute and chronically. In acute course - the bird refuses to feed (anorexia), plumage becomes tousled, eyes are closed, head is down, chickens lose egg production. Visible mucous membranes are hyperemic and edematous, in a separate sick bird a viscous mucous exudate flows from a slightly open beak, nasal openings are sealed with inflammatory exudate. Some sick chickens have swelling of the front of the earrings due to stagnation and intoxication. The comb and earrings are dark purple in color. Breathing becomes quickened and hoarse, body temperature rises to 44 ° C, and before the case drops to 30 ° C. If the disease in chickens is caused by highly pathogenic influenza viruses, then as a rule 100% of chickens die. Subacute and chronic course of influenza lasts from 10 to 25 days; however, the outcome of the disease depends on the resistance of the diseased bird. Mortality reaches 5-20%. With this form of influenza in a sick bird, along with respiratory symptoms, diarrhea occurs, the litter becomes liquid, colored in brown-green. In addition to the above signs, a sick bird has ataxia, convulsions, necrosis, manege movements, tonic clonic muscle cramps of the neck and wings in the pre-agonal stage. In cases of infection with low pathogenic strains, cases of a chronic course of the disease without pronounced clinical signs are possible.

Pathological changes. Pathological changes vary widely over the course of the disease. The most typical sign for influenza is a picture of hemorrhagic diathesis, accompanied by subcutaneous edema in the pharynx, larynx, neck, chest, legs, which contain gelatinous exudate. These edema in birds result from a violation of the function of the circulatory system. Both massive and single hemorrhages under the skin, into muscles, into parenchymal organs and mucous membranes are noted; in laying hens, hemorrhages in the ovary and oviduct. Permanent pathological signs of influenza are gastroenteritis, bronchitis, pericarditis, peritonitis, aerosaculitis, pulmonary edema, congestion in the internal organs. Pathological changes in the brain are especially characteristic of influenza: hemorrhagic meningitis, diffuse hemorrhages, foci of edema in the softening of the brain substance.

Diagnosis. To make a final diagnosis, a set of laboratory virological studies is necessary. Pathological material (liver, lungs, brain, etc.) is sent to the laboratory from birds that died in the acute stage of the disease. For serological studies, chickens are taken paired blood serum at different periods of the disease. In the laboratory, for the isolation of the virus, chicken embryo infection methods are used, and for the identification of the isolated virus - RGA, RTGA and CSC. A biological sample is placed on chickens 60-120 days of age. For retrospective diagnosis using RTGA, RDP, ELISA and PCR. A diagnosis of avian influenza is considered confirmed if: a highly pathogenic virus is isolated and identified; any virus of subtypes H5 or H7 is isolated and identified; the presence of ribonucleic acid (RNA) specific for a highly pathogenic virus of any subtype or RNA of viruses of subtypes H5 or H7, of any level of pathogenicity in samples of pathological material was established; antibodies to hemagglutinins of subtypes H5 and H7 were detected when it is reliably known that they are not associated with vaccination.Differential diagnosis . The generalized septicemic form of influenza is differentiable from Newcastle disease. The respiratory form is from infectious bronchitis, mycoplasmosis, laryngotrtacheitis and other respiratory diseases of birds.

Immunity and specific prevention. An ill bird acquires non-sterile immunity, which lasts up to 6 months. To prevent highly pathogenic avian influenza in Russia, inactivated vaccines are used as the most epidemiologically safe. For specific prophylaxis, inactivated hydroxide-aluminum hydroxylamine embryo vaccine type A, liquid and dry inactivated vaccines against bird flu are used.

Control measures. In a dysfunctional poultry house, the sick and suspicious birds are discarded, killed in a bloodless manner and disposed of. Conditionally healthy livestock is killed for meat. Spend a thorough disinfection of the room. In case of bird flu (on farms) disease of birds with influenza caused by highly pathogenic viruses, approve a special commission to combat bird flu, which introduces a strict sanitary regime of the farm; develops a set of measures aimed at eliminating and preventing the spread of the disease, which includes the destruction of carriers (migratory and waterfowl); the issue of vaccination in threatened points and zones is being addressed; establishes the terms of rehabilitation and manning of such farms with poultry, based on the specific conditions of the farm; solves the issues of possible protection of people from infection and their vaccination against human flu. Quarantine in a dysfunctional point can be canceled no earlier than 21 days from the day of destruction (disposal) of the entire susceptible livestock or slaughter and processing of conditionally healthy birds that were in a dysfunctional point and the final disinfection. The quarantine in the organization in which the poultry was suspected of being infected with bird flu or was processed and stored, and the raw materials from such poultry are canceled no earlier than 21 days after the end of poultry meat processing and the final disinfection of the organization’s premises, its territory, inventory, and production equipment. After quarantine has been lifted for 3 months, all bird owners should restrict the export of hatching eggs and live birds of all species and ages to other farms. Vaccination of a poultry head against avian influenza after quarantine cancellation should be carried out in a dysfunctional area for a period of time until laboratory monitoring confirms the absence of virus circulation among the vaccinated livestock.

Personnel protection measures. All individuals involved in special activities to eradicate the avian influenza disease are advised to undergo a daily medical examination. To work with sick birds, specialists should be provided with overalls (bathrobes or overalls, towels, hats), replaceable shoes, rubber gloves, respirators, soap and other personal protective equipment, as well as necessary tools and utensils. At the end of work, clothes and shoes are disinfected or destroyed. After a clinical examination of animals or sampling of the material, you need to wash your face and wash your hands with soap. For personal disinfection of workers, tools and utensils use the means and methods prescribed for the disinfection of various objects infected with pathogenic microorganisms. Persons who have had serious illnesses, have diseases of the respiratory system, persons aged 65 and under 18 years old, pregnant women should not be allowed to work with sick birds.

Bird flu is an acute zoonotic infectious disease with a predominantly fecal-oral pathogen transmission mechanism. It is characterized by severe febrile intoxication syndrome, lung damage with the development of RDS and high mortality.

ICD Code 10

J10. Influenza caused by an identified virus.

Etiology (reasons) of bird flu

The causative agent is influenza A virus of the genus Influenzavirus of the Orthomyxoviridae family. It belongs to enveloped viruses. The virion has an irregular or oval shape, is covered with a lipid membrane penetrated by glycoprotein spikes (spicules). They determine the hemagglutinating (H) or neuraminidase (N) activity of the virus and act as its main antigens. There are 15 (according to some reports, 16) hemagglutinin variants and 9 neuraminidases. Their combination determines the presence of virus subtypes, and theoretically, 256 combinations are possible. Modern “human” influenza virus has a combination of antigens H1, H2, H3 and N1, N2. According to seroarchaeological research, a severe pandemic of 1889-1890. was caused by the subtype H2N2, a mild epidemic of 1900–1903. - subtype H3N2, pandemic "Spaniard" 1918-1919. - H1N1 containing additional protein obtained from avian influenza virus.

Epizootics of avian influenza in recent years are associated with the subtypes H5N1, H5N2, H5N8, H5N9, H7N1, H7N3, H7N4, H7N7. In wild bird populations, the subtypes H1, H2, H3, N2, N4 circulate, i.e. similar to human influenza A virus. Under the lipid membrane is a layer of the matrix protein M-protein.

The nucleocapsid located under the bilayer membrane is organized according to the type of spiral symmetry. The genome is represented by single-stranded RNA, consisting of eight separate segments. One of the segments encodes the non-structural proteins NS1 and NS2, the rest encodes the virion proteins. The main ones are NP, which performs regulatory functions, M-protein, which plays an important role in the morphogenesis of the virus and protects its genome, and internal proteins - P1 transcriptase, P2 endonuclease, and B3 replicase. Differences in the structural proteins of the bird flu virus and human flu represent an insurmountable species barrier that impedes the replication of the bird flu virus in the human body.

Different subtypes of this virus have unequal virulence.

The most virulent subtype is H5N1, which in recent years has acquired a number of unusual properties:

High pathogenicity for humans;
  - the ability to directly infect people;
  - the ability to cause overproduction of pro-inflammatory cytokines, accompanied by the development of acute RDS;
  - the ability to cause multi-organ disorders, including damage to the brain, liver, kidneys and other organs;
  - resistance to the antiviral drug rimantadine;
  - resistance to interferon.

The avian influenza virus, in contrast to that of the human virus, is more stable in the environment. At a temperature of 36 ° C, it dies in three hours, 60 ° C - in 30 minutes, with the heat treatment of food products (boiling, frying) - instantly. It tolerates freezing. In bird droppings, it survives up to three months, in water at a temperature of 22 ° C - four days, and at 0 ° C - more than a month. In carcasses of birds remains active for up to a year. Inactivated by conventional disinfectants.

Bird Flu Epidemiology

The main reservoir of the virus in nature  - migratory waterfowl belonging to the orders Anseriformes (wild ducks and geese) and Charadriiformes (herons, plovers and terns). Of greatest importance are wild ducks. Influenza viruses in Eurasia and America evolve independently, so migration between continents does not play a role in the spread of the virus, long-distance flights are crucial. For Russia, the Central Asian – Indian and East Asian – Australian migration routes are important in this regard. These include routes to Siberia via Malaysia, Hong Kong and China, i.e. regions where there is an intensive formation of new variants of the virus. Less significant are the East African-European and West Pacific routes.

In wild waterfowl, the virus does not cause a clinically pronounced disease, although large-scale severe influenza epizootia in polar terns has been described. The replication of the virus in birds occurs mainly in the intestine and, accordingly, it is released into the environment with feces, to a lesser extent with saliva and respiratory material. 1 g of feces contains a sufficient amount of virus to infect 1 million heads of poultry.

The main mechanism of virus transmission in birds- fecal-oral.

Waterfowl (ducks) are able to transmit the virus transovarially and, thus, serve as its natural reservoir and spread along its migration routes. They are the main source of infection for poultry, which, on the contrary, suffer from severe forms of influenza, accompanied by their mass death (up to 90%). The most dangerous subtype is H5N1. Infection occurs in conditions of free detention and the possibility of contact with their wild counterparts. This is especially true for the countries of Southeast Asia (China, Hong Kong, Thailand, Vietnam and other states). There, along with large poultry farms, there are many small peasant farms.

The bird flu virus can infect mammals: fur seals, whales, minks, horses and, most importantly, pigs. Cases of virus penetration into the population of the latter were noted in 1970, 1976, 1996 and 2004. These animals can also be affected by the human flu virus. Currently, the susceptibility of people to such bird viruses is low. All cases of infection were recorded in those who had long and close contact with a sick bird. A UK experiment on introducing various subtypes of the virus into the body of volunteers gave a negative result.

In Thailand, with a population of 60 million people, 12 cases of the disease have been reliably detected during an epizootic that has affected two million birds. By 2007, about 300 episodes of bird flu in humans have been registered. Officially recorded two cases of infection from a sick person.

These data suggest that circulating strains of avian influenza virus do not pose a serious threat to humans. Thus, we can conclude that the interspecific barrier is quite strong.

Even isolated cases of infection of people from birds and from patients indicate that the insurmountability of the interspecific barrier is not absolute.
The actual number of cases of infection from poultry, and possibly from sick people, given the real situation in regions where epizootics are rampant, can be many times more. During the H7N7 flu epizootic in the Netherlands, 77 people fell ill, one died. Persons in contact with patients showed high antibody titers, which also indicates the possibility of transmission of the virus from person to person, but with a loss of virulence.

Secondly, the mutagenic potential of avian influenza virus, especially the H5N1 subtype, is very large.

Thirdly, pigs are susceptible to avian influenza and human influenza viruses, so it seems theoretically possible for pathogens to meet in the animal. Under these conditions, their hybridization and the occurrence of assortant viruses with high virulence inherent in avian influenza virus and at the same time capable of being transmitted from person to person can occur. Due to the massive spread of avian influenza, this probability has increased dramatically.

Cases of human infection with swine flu have also been described, but the simultaneous penetration of two viruses into the human body is still less likely.

Fourth, genetic methods have proven that the Spanish pandemic of 1918-1919. had a "bird" origin.

Fifth, in modern conditions, thanks to the processes of globalization, the availability of fast modes of transport, the possibility of the spread of the assortant virus is increasing dramatically. Thus, it is fair to conclude that the likelihood of a new variant of the influenza A virus and the occurrence of a severe pandemic is very high.

Using mathematical modeling methods, it was shown that in a city with a population of seven million (Hong Kong), the number of cases at the peak of the epidemic can reach 365 thousand people daily (for comparison, in Moscow during the influenza pandemic in 1957 this number did not exceed 110 thousand people per day ) According to WHO experts, it is possible that a quick culling of birds during an epizootic in Hong Kong in 1997 prevented an influenza pandemic. US experts predict that in the event of a pandemic in America, it will be necessary to hospitalize from 314 to 734 thousand people, die from 89 to 207 thousand.

Pathogenesis of avian influenza in humans

Currently, the mechanism of development of influenza caused by the H5N1 virus in humans is not well understood. It was established that the place of its replication is not only epithelial cells of the respiratory tract, but also enterocytes. Taking into account general biological and immunopathological processes, it can be assumed that the pathogenesis of influenza A (H5N1) in humans will develop according to the same mechanisms.

Various hemagglutinins of avian influenza viruses are distinguished by their ability to recognize and bind to the receptor - sialic acid, bound in the oligosaccharide of cell membranes with galactose. The hemagglutinins of human influenza viruses interact with the residues of this acid, combined with a 2.6 link to galactose, and the hemagglutinin of avian influenza viruses recognizes it in 2.3 bonds with galactose residues. The type of terminal sialic acid bond and the conformational mobility of surface lectins oligosaccharides are the main elements of the interspecific barrier for avian and human influenza viruses. Lectins of human tracheal epithelial cells include lectins with a binding type of 2.6 and do not contain oligosaccharides with a binding type of 2.3, characteristic of epithelial cells of the intestinal tract and respiratory tract of birds. Changes in the biological properties of the highly pathogenic strain of virus A (H5N1), the appearance of its ability to overcome the interspecific barrier can lead to the defeat of various types of cells in humans with the development of more severe forms of the disease. In the clinical picture of such pathologies, along with the catarrhal syndrome, gastrointestinal damage develops.

The clinical picture (symptoms) of bird flu

The incubation period for influenza A (H5N1) is 2-3 days with fluctuations from 1 to 7 days.

The main symptoms and dynamics of their development

The onset of the disease is acute. Symptoms of intoxication are expressed. The body temperature rises to 38 ° C from the first hours of the disease, often reaching hyperpyretic values. The febrile period is extended to 10-12 days, and in severe cases with a fatal outcome - until the last hours of the patient's life. Chills, muscle and joint pain are characteristic. In the midst of the disease (2nd – 3rd day), the catarrhal syndrome joins, manifested by the development of bronchitis, bronchiolitis, laryngitis; there may be signs of rhinitis. Sore throat and "flaming" oropharyngitis are characteristic. During this period, most patients develop primary viral pneumonia. At the same time, shortness of breath, a wet cough with sputum, possibly with an admixture of blood, appear. Harsh breathing, moist rales of various sizes, crepitus are heard over the lungs.

On a chest x-ray in the early stages, nonspecific changes in the form of diffuse, multifocal, or individual infiltrates are determined, which tend to rapidly spread and merge. In some cases, segmental or lobar seals may be detected. Characteristic is a progressive course, an increase in shortness of breath and the development of RDS. Along with intoxication and catarrhal syndrome, a gastrointestinal tract lesion develops, manifested by repeated vomiting, secretory diarrhea, and abdominal pain. Perhaps an increase in the liver, accompanied by an increase in the activity of serum transferases. A third of patients develop acute renal failure, creatininemia.

In most patients, signs of damage to the nervous system are determined, impaired consciousness, the development of encephalitis are possible.

Leukopenia, lymphopenia, thrombocytopenia are recorded in the hemogram.

There may be variants of the course of the disease with fever, diarrhea and the absence of signs of damage to the respiratory system.

Bird Flu Complications

Infection is dangerous by the development of viral pneumonia, damage to the kidneys, liver, and blood-forming organs. It is these consequences that often lead to the death of patients. It has been established that the place of replication of the H5N1 subtype influenza virus in humans (at least in those who died as a result of the disease) is not only the respiratory tract, but also the intestine.

Risk factors for developing severe forms of influenza A (H5N1) in humans:

Age of the patient (in children five years of age and younger, the symptoms of the disease are mild);
  - the duration of the manifestation of the disease before hospitalization (delay from hospitalization);
  - the anatomical level of damage to the respiratory tract;
  - the degree of leukopenia of peripheral blood;
  - the presence of multiple organ dysfunction.

Mortality and causes of death

Mortality is 50–80%. Most often, patients die from complications in the second week of the disease.

Diagnosis of bird flu

Correct diagnosis in the early stages is the starting point for organizing targeted treatment, timely anti-epidemic measures and determining the prognosis. However, there are certain objective difficulties associated with the similarity of the clinical picture of this disease and other acute respiratory viral infections in the diagnosis of avian influenza.

A preliminary diagnosis of influenza A (H5N1) can be made on the basis of the following epidemiological history and clinical manifestations:

The presence of outbreaks of influenza A (H5N1) among bird and animal populations or cases of death of poultry in the patient's region of residence;
- contact with a sick person whose infection with the influenza virus (H5N1) is confirmed, seven days before the onset of the first clinical signs;
  - contact with a patient with acute respiratory infections of unknown etiology, including those ending fatally, seven days before the onset of the first clinical signs;
  - indication of the patient to travel to a country or territory where there are reports of an unfavorable epidemiological and / or epizootic situation for influenza A (H5N1);
  - the presence of a professional risk of infection of the patient;
  - high fever in combination with difficulty breathing, coughing;
  - diarrhea (in the absence of blood impurities in the feces).

The final diagnosis can be made after laboratory confirmation.

Laboratory diagnostics is based on virological methods, serological reactions, immunofluorescence analysis and PCR.

Differential diagnosis

Considering that in case of influenza A (H5N1) there are symptoms of respiratory tract damage, it is necessary to conduct differential diagnosis with other acute respiratory viral infections: “traditional” influenza (A, B), severe acute respiratory syndrome, parainfluenza, respiratory syncytial, adenovirus and enterovirus infections, and also legionellosis and ornithosis.

Indications for consultation of other specialists

With the development of ODN - consultation of a resuscitator.

Diagnosis example

J10. Influenza caused by H5N1 virus, severe course; complication - pneumonia, ONE.

Indications for hospitalization

The clinical picture of a respiratory infection in a patient who had contact with a sick bird.

Bird Flu Treatment

Mode. Diet

When confirming the diagnosis of influenza A (H5N1), treatment is carried out in a boxed department of the hospital. During the acute period of the disease, bed rest is necessary. A complete diet rich in vitamins and containing a sufficient amount of fluid is recommended.

Drug therapy

Etiotropic therapy

Of the etiotropic drugs, oseltamivir (Tamiflu), an antiviral drug belonging to the class of neuraminidase inhibitors, is currently the most effective. It is prescribed at a dose of 75 mg orally twice a day for seven days. Possible dose increase to 300 mg. Rimantadine (remantadine, algir) can also be used.

Pathogenetic agents

In pathogenetic therapy, detoxification plays a leading role. According to clinical indications, intravenous administration of crystalloid solutions is used to correct acid-base balance and electrolyte balance.

In severe clinical forms of the disease, glucocorticoids, aprotinins are indicated. With the development of ARDS, treatment is carried out in the intensive care unit with mandatory respiratory support, surfactant is administered. Symptomatic therapy is carried out according to indications.

Convalescents are discharged from the hospital no earlier than seven days after the restoration of normal body temperature.

All those in contact with patients with influenza A (H5, N1) are shown medical supervision for seven days, with a measurement of body temperature twice a day. If it increases, the appearance of cough and shortness of breath should immediately seek medical help.

Forecast

The prognosis of the disease is unfavorable. Mortality is 50–80% in the second week of illness.

Preventive measures

Specific

Global monitoring under the auspices of WHO allows you to quickly detect a dangerous virus and begin mass production of vaccines. Mass vaccination can be started after nine months. At present, it is important to conduct high-quality anti-epidemic measures aimed at reducing the prevalence of human flu. In particular, it is necessary to increase the number of vaccinees, which will reduce the incidence rate, and possibly susceptibility to a new variant of the virus. Some countries produce a limited amount of vaccine against antigenic variants of the virus. According to forecasts, they are the most likely candidates for a new pandemic virus.

The main method of combating bird flu is the complete extermination of the number of birds on infected farms, and those who come into contact with them and carry out their destruction must work in respirators and overalls. Disinfection with the use of quaternary ammonium compounds non-toxic to humans (acepur) is of great importance. They are easily neutralized by soaps and other detergents. They conduct quarantine measures and prohibit the export of poultry and eggs from affected regions. In surrounding farms and poultry farms vaccination is carried out, but its effectiveness and feasibility are doubtful. The presence of antibodies in vaccinated birds makes monitoring difficult, as it does not allow differentiating with infection; there is also evidence that vaccination promotes the mutation of the virus.

In Russia, the introduction of infection is possible with migratory birds. However, agricultural conditions in Russia (mainly closed poultry keeping, low probability of contact with pigs, less close contact between people and animals than in Southeast Asia) can virtually eliminate the possibility of an assortant virus. In this regard, the main activities should be aimed at preventing the transmission of the virus from countries where it can appear. To do this, tighten sanitary control at the border, recommend wearing respiratory masks, their preventive effectiveness reaches 98%.