Bird flu: symptoms in humans. Treatment, prevention, first signs. Bird flu

Avian influenza is a viral infection that affects both birds and humans and is highly contagious. Sometimes this disease occurs with virtually no symptoms, but even in this case the risk of complications and even death is quite high. The signs and causes of this disease, its treatment and preventive measures should be discussed separately.

Avian influenza is a viral infection that affects both birds and humans

The main carrier of bird flu, as you might guess from the name of the disease, is birds. In most cases, we are talking about wild representatives of the avian species - especially waterfowl. These birds constantly migrate and, therefore, carry the infection over fairly long distances. As for the poultry that most often suffer from this infection, these are turkeys and chickens.

People first started talking about the disease described in 1997, because it was then that a large number of people caught the infection - the epidemic was recorded in Hong Kong and 60 percent of all patients eventually died. The virus received the scientific name - H5N1, and soon significantly expanded its geography, spreading not only to Asian and African, but also to European countries.

If earlier the infection was noted only in birds, now people have begun to suffer from it. Like other influenza viruses, it continued to mutate. The year 2003 in the Netherlands, for example, was marked by a small epidemic outbreak of H7N7, during which almost nine dozen people fell ill with this disease (and even one death was recorded).

2013 in China was marked by an outbreak of H7N9, when the disease was diagnosed in 130 people, about three dozen of whom died. According to WHO statistics, in the fall of 2013 the H7N7 virus was detected on some Italian farms; several hundred thousand poultry had to be culled.

The H7N9 virus, which is considered pathogenic for humans, is observed quite often in China. But an epidemic of bird flu can begin in every country and on any continent, so one should not forget about the danger of this disease - especially since the virus does not stop mutating, becoming more and more complex and adapting to ways of fighting against it.

Features of the virus

Before we talk about the symptoms of bird flu, we should tell you more about this infectious family. The viral structure turns out to be quite complex: the outer shell consists of RNA and two proteins (neuraminidase and hemagglutin):

• For example, hemagglutin attaches the viral agent to a healthy cell and produces antibodies that protect the virus.
• Neuraminidase helps the infection penetrate a healthy cell and begin to reproduce in it.

Scientists have been able to identify several antigenic types of this pathogen: H7N7 causes the development of “chicken plague”. As for H5N1, it causes mass deaths of chickens. That is, these types are considered the most pathogenic for poultry (after infection, all sick people die within two days). But, however, there are also low-pathogenic strains that are more or less easily tolerated by patients.

How pathogenic is avian influenza in humans? The mutation of these viruses has made them dangerous for humans. Moreover, quite severe forms of the disease are diagnosed: sometimes it even happens that death occurs in a lightning-fast course.

The infection is localized in the intestines and comes out along with feces.

As for the mechanics of infection, it is aerogenic, that is, airborne. Quite often, the cause of infection is contact with an infected bird. Moreover, not necessarily with the living, but also with the dead. But people do not transmit the described infection among themselves (at least, no such cases have been registered to date).

The infection is localized in the intestines

How does the disease manifest in birds?

The symptoms of this infection in chickens, turkeys and other birds, as well as in people, need to be discussed separately. So in chickens that have contracted this infection:

• egg production decreases sharply;
• anorexia is possible (since appetite completely disappears);
• appearance deteriorates (for example, feathers look ruffled);
• inflammation of the mucous tissue begins;
• secreted mucus clogs the airways;
• the bird suffers from wheezing and intermittent breathing;
• temperature indicators increase (up to 44 degrees);
• diarrhea begins - and the color of the droppings is brown-green;
• seizures may develop;
• there is a danger of neurosis.

First of all, the symptoms of bird flu in chickens relate to damage to the nervous system, as a result of which coordination of movements is impaired. Birds stagger, it is difficult for them to step on their hind limbs, and frequent falls are possible. The wings and necks bend, acquiring an unnatural position. The bird stops reacting normally to certain external stimuli. They are tormented by severe thirst. There is a real danger of pulmonary edema, which, in turn, can result in death. The described disease is also called chicken influenza infection, although it occurs in turkeys even more often than in chickens, according to statistics. Birds such as geese, pigeons, ducks, and so on are also susceptible to it.

Symptoms and danger of the disease

Is bird flu dangerous for humans? Undoubtedly. How? First of all, with dangerous consequences.

The incubation period of this disease is usually 3 days, but in some cases it reaches 8 days or even a couple of weeks.

Signs of the disease can be considered based on the following syndromes:

• infectious-toxic;
• respiratory;
• gastrointestinal.

The disease, as a rule, begins quite acutely - the patient suffers from:

• severe chills;
• nasal discharge;
• sore throat;
• pain in the muscles;
• migraine.

There may be upset stool (it becomes watery). The patient vomits frequently. From the early days, temperatures rise to 38 degrees and above. After a couple of days, respiratory syndrome is possible. Among the complications, there is the danger of primary pneumonia (which is characterized by a cough with clear sputum, blood impurities and shortness of breath). The listening doctor will probably hear the presence of moist rales and excessive harshness of breathing.

A chest x-ray shows inflammatory infiltrates, which are particularly extensive, quickly merging and spreading beyond the boundaries of the initial inflamed focus. The formation of lobar seals is possible.

If you do not treat the disease, start therapy late or choose the wrong treatment course, dangerous complications will develop, such as:

• distress syndrome;
• respiratory failure;
• inflammatory processes in lung tissues.

The final outcome could be fatal.

Bird flu is dangerous even for humans

Complications of the disease

One of the main symptoms of the development of the avian influenza virus is distress syndrome. A blood test of a sick person shows a reduced number of leukocytes, as well as platelets and lymphocytes.

In addition, this disease can result in disruption of the normal functioning of some internal organs (the kidneys and liver are especially affected). About a third of all patients experience kidney failure. Blood tests show elevated creatinine.

The described disease manifests itself quite severely in humans - especially if it concerns small children who have not yet reached the age of three. There is a possible risk of overcoming the blood-brain barrier with the subsequent development of encephalitis. All this is accompanied by severe migraine, vomiting, and sometimes consciousness is impaired.

The treatment prognosis turns out to be quite unfavorable: in 60 percent of cases, death is likely (and already in the second week of the disease).

Moreover, complications cannot be avoided if:

• seeking medical help will be untimely;
• immunodeficiency is observed (leukocyte counts are too low);
• there are concomitant diseases.

That is why treatment should begin immediately after the first symptoms appear. And since only a qualified doctor can make an accurate diagnosis, do not hesitate to contact him.

When the infection has been successfully transferred, a person acquires immunity, which is short-lived. That is, next season there is every chance of getting infected again.

All this also speaks to the need to prevent such a disease in people. Typically, outbreaks of influenza infection among birds in one place or another are registered, after which all necessary measures are taken to ensure that the infection does not spread among people.

Symptoms that should alert you

Here are the first signs of this disease in adults, observing which you should be alarmed and consult a doctor:

• fever, cough, difficulty breathing;
• upset stool (although there is no blood in the feces);
• Symptoms of influenza infection quickly become more and more severe.

But finding out an accurate diagnosis and confirming the presence of the disease will only be possible through:

• immunological technique;
• molecular genetic techniques;
• virological technique.

And only after realizing that it is, in fact, H5N1, you need to know how to treat it.

The rise in temperature should already be alarming

Is it possible to eat infected poultry?

Is it possible to eat poultry without fear of getting avian flu? Yes. If the meat is cooked correctly, it is safe to eat. At temperatures exceeding 70 degrees Celsius, the infection dies.

However, infection is possible during the preparation of an infected individual, which will have to be plucked and gutted. In addition, viral agents may be present in avian feces and secretions. The infection is also transmitted by airborne droplets - a person simply inhales its smallest particles that rise into the air or end up on some surfaces.

Treatment process

Treatment of the described disease in humans involves:

• carrying out regime measures - hospitalization and discharge only in cases where the temperature returns to normal (with adequate therapy and the absence of complications, this should be within a week);
• the use of antiviral drugs that are multifunctional (like Tamiflu or Relenza);
• the use of medications for symptomatic treatment (if the temperature rises above 38.5 degrees, it can be brought down with antipyretics - Paracetamol or Ibuprofen). These same drugs enhance the effectiveness of antiviral therapy.

However, there are certain medications that are not used when treating H5N1. In particular, you should avoid Aspirin and anti-influenza medications.

As for antibiotics, they are usually prescribed when mixed pneumonia (which is not only viral, but also bacterial in nature) is diagnosed.

When the inflammatory process in the lungs becomes severe, the doctor prescribes hormonal medications.

If we talk about emergency preventive medications, the use of Cycloferon, Amiksin, as well as other interferon inducers will help. These drugs are recommended to be taken at initial suspicions of the disease: moreover, they are useful for those who belong to the risk group and for everyone who, as part of their profession, comes into contact with infected birds.

Prevention

Knowing how bird flu is transmitted, this infection can be avoided. This is why the issue of prevention is so important.

Perhaps the most effective preventive method remains vaccination. It is especially shown:

• those who come into contact with poultry and work on poultry farms;
• healthcare workers exposed to people infected with H5N

As a rule, standard vaccines are used; a specific vaccination directly against this disease has not yet been invented.

For chemoprophylaxis, interferon inducers are prescribed: for example, Tamiflu is excellent.

Most of all, doctors fear further mutation of the virus so that it does not become transmitted between people. If this happens, the likelihood of a severe pandemic is high.

Separate measures are being taken to prevent this disease in birds. In particular:

• poultry is vaccinated (although this method cannot be called one hundred percent protection);
• young animals, as well as new individuals, are quarantined;
• closed pens are created so that poultry does not come into contact with wild birds;
• strict control of personnel working on poultry farms is carried out;
• Close monitoring is carried out to ensure that there are no dogs or cats on the premises.

Vaccinating birds helps prevent infection

By avoiding the development of influenza infection among chickens and other birds, a person will protect his own health. This disease is very dangerous for the human body, and therefore it is necessary to begin treatment when the first symptoms appear. But you shouldn’t diagnose yourself, otherwise you risk making a mistake and treating something that’s not what you should be treating.

Good afternoon, dear readers. What is bird flu and how dangerous is it for humans? Among the problems of infectology left as a legacy to the 21st century by the last century, viral infections occupy an exceptional place. They account for more than 80% of all human infectious diseases, the number of which is steadily growing.

Not only is the epidemic process of “classical” infectious diseases intensifying, but new types of pathogens are appearing (prions, virus mutants, etc.), which cause outbreaks and epidemics of often particularly dangerous infections with high rates of mortality and disability among patients (slow infections, avian flu , hemorrhagic fevers, etc.).

Bird flu was first identified in Italy almost a hundred years ago, and in 1925 its epidemic was registered in Japan, the Republic of Korea and Vietnam. Since 1959, 21 outbreaks of this infection have been registered in various regions of the world (mainly in Europe and America), 5 epidemics occurred on poultry farms in Australia.

Since mid-December 2003, the global epidemic situation with avian influenza has become more complicated - it was already registered in 8 countries (Republic of Korea - 2003, Vietnam - 2004; Japan - 2004; Thailand - 2004; Cambodia - 2004 .; China - 2004; Laos - 2004; Indonesia - 2004).

Since the first report of the appearance of this infection in the 21st century in the Republic of Korea (December 12, 2003), during January-February it spread within the above-mentioned Asian countries, continuing to spread in other regions of the planet.

Everyone knows that influenza is the most common infectious disease in humans, which occurs with severe intoxication and complications, affecting the upper respiratory tract. However, not everyone knows that influenza is a disease not only of humans, but also of animals, including birds.

What virus causes bird flu?

Influenza in animals, birds and influenza in humans is caused by related viruses, which differ only in the composition and aggressiveness of their enzymes, namely the type of hemagglutinin and neuraminidase. It should be noted that the ability of a particular strain of influenza virus to cause diseases in humans or animals depends on the type of hemagglutinin and neuraminidase.

Pathogenic for humans are those strains of the virus that contain hemagglutinin of the first - third (H1 - H3) and neuraminidase of the first and second (N1 - N2) types.

In turn, diseases in animals and birds are caused by influenza viruses that contain hemagglutinin from the fourth to tenth (H4 - H10) and neuraminidase from the third to eighth (N3 - N8) types. It is believed that human infection with animal and bird virus strains is impossible.

Of the 16 currently known influenza strains that infect birds, the most pathogenic for birds are the H5N1 and H7N7 strains. For many bird species, infection with this virus is absolutely fatal.

Bird flu H5N1 and H7N7 poses a particular threat to wild waterfowl and domestic birds - chickens, ducks, geese, turkeys, which generally have no immunity to this disease and quickly die after infection.

Don't people get bird flu?

The exception is avian influenza caused by the H5N1 strain. Cases of the disease have been registered among people since 1997. As a rule, this is extremely atypical and is an isolated case of the disease, since the susceptibility of people to this strain of the influenza virus is also not high.

Infection mainly occurs through direct contact with infected birds during and at poultry farms, cutting their carcasses, collecting and packaging eggs.

Much less often, infection occurs through eating raw or undercooked eggs.

Recently, there have been reports of the possibility of airborne transmission of the H5N1 influenza virus from birds to humans.

There is no proven human-to-human transmission of bird flu yet. However, the concern is that due to mutations and the exchange of genetic material with human influenza viruses, avian influenza viruses can acquire new properties and be transmitted from person to person, including by airborne droplets.

In such a situation, bird flu can turn into a monster that will pose a serious danger to humanity!

The clinical symptoms of avian and “regular” influenza in humans are similar.

Symptoms of bird flu in humans

With bird flu, an average of 2-4 days pass from infection to the first clinical manifestations. Characteristic symptoms are high fever, dry cough, sore throat, muscle pain, migraine. In many cases, diarrhea, nausea, and vomiting are observed.

If the course is favorable, recovery occurs after seven to ten days. However, more often, avian influenza in humans becomes severe with the development of atypical (viral) pneumonia, acute pulmonary failure and ends in the death of the patient.

Treatment of avian influenza in humans

Treatment of avian influenza in humans is carried out in the same way as treatment of “regular” influenza.

The same drugs are used: antiviral, antipyretic, anti-inflammatory, expectorant, desensitizing, and the like.

In case of severe course or development of complications, treatment is carried out in intensive care and resuscitation departments.

Prevention

To prevent bird flu, you must adhere to the following recommendations:

• avoid contact with droppings, secretions, corpses of wild and domestic birds, even if these are isolated cases of their death;
• when in places where birds die, use cotton-gauze bandages and do not touch the mucous membranes of the eyes, mouth and nose with your hands;
• buy poultry meat in specialized departments of stores and markets;
• Consume poultry meat and eggs only after proper heat treatment.

Important to remember! If symptoms of an acute respiratory disease appear within 5 days of being in the place where the birds died, you should definitely seek the help of a doctor.

Antiviral therapy started in the first days of illness with avian influenza significantly increases the chances of recovery.

Good luck and health to you!

44.1 clinic, diagnosis, treatment

Flu– ARVI caused by influenza viruses. In addition to humans, many mammals (horses, pigs, dogs, cattle) and birds suffer from it.

Epidemiology of avian: the source of human disease is only a sick person. However, hybridization of animal and human viruses is possible, which leads to variability of the pathogen and the emergence of pandemic-dangerous strains.

In nature, the main reservoir of influenza viruses is aquatic and semi-aquatic birds; all the genes of the viruses that caused epidemics are isolated from them. During circulation in natural biocenoses, the genes of avian influenza viruses are reassorted with the genes of human influenza viruses with the formation of a variant with new antigenic properties

Etiology of avian influenza: Influenza virus (type A) from the Orthomyxoviridae family, strain H5N1 (avian influenza).

Pathogenesis: based on damage to the vascular system, which occurs as a result of the toxic effect of the virus and is manifested by increased vascular permeability, fragility of their walls, impaired microcirculation, which leads to the development of early changes in the lungs (edema of the lung tissue and multiple hemorrhages in the alveoli and interstitium of the lung), and also plays a role in the development of neurological syndromes.

Clinic: incubation period 3 days (from 2 to 4 days). The first symptoms are fever (more than 38°C), shortness of breath and cough (in half of the patients it is productive, in 30% - sputum mixed with blood), headache, vomiting, in 70% - diarrhea (watery stools, without mucus and blood). There are no complaints of sore throat, conjunctivitis, rash, or runny nose. Mortality up to 80%.

X-ray of the lungs: pronounced bilateral infiltration, areas of tissue compaction, atelectasis.

Hemogram: lymphopenia 250-1100/µl, thrombocytopenia 45000-150000/µl.

Diagnostics: studies to identify the H5N1 strain are indicated in the following cases:

1. X-ray confirmed pneumonia, acute respiratory distress syndrome, other respiratory diseases of unknown origin.

2. History of travel within 10 days before the onset of symptoms to one of the countries where H5N1 avian influenza is reported in humans or birds

Or: 1. fever above 38°C 2. Cough, sore throat or shortness of breath 3. History of contact with poultry or wild birds, a patient with or suspected of influenza A (H5N1) or travel to countries with H5N1 within 10 days before the onset of illness

Treatment– antiviral therapy: oseltamavir (for the treatment of patients over 1 year of age and for prophylaxis in persons over 13 years of age), zanamivir (for the treatment of patients over 7 years of age).

Pathogenetic and symptomatic therapy - see question 16.1.

Avian influenza is an acute zoonotic infectious disease with a predominantly fecal-oral transmission mechanism. It is characterized by a pronounced feverish-intoxication syndrome, lung damage with the development of RDS and high mortality.

ICD 10 code

J10. Influenza caused by an identified virus.

Etiology (causes) of avian influenza

The causative agent is the influenza A virus of the genus Influenzavirus of the Orthomyxoviridae family. It is classified as an enveloped virus. The virion has an irregular or oval shape, 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 sources, 16) variants of hemagglutinin and 9 variants of neuraminidase. Their combination determines the presence of virus subtypes, with 256 combinations theoretically possible. The modern “human” influenza virus has combinations of antigens H1, H2, H3 and N1, N2. According to seroarchaeological research, the severe pandemic of 1889–1890. was caused by the H2N2 subtype, moderate epidemic 1900–1903. - subtype H3N2, Spanish flu pandemic of 1918–1919. - H1N1, containing an additional protein derived from the avian influenza virus.

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

The nucleocapsid, located under a two-layer shell, is organized according to helical symmetry. The genome is a single-stranded RNA consisting of eight separate segments. One of the segments encodes the nonstructural proteins NS1 and NS2, the rest encode 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 avian influenza virus and human influenza represent a difficult species barrier that prevents the replication of the avian influenza virus in the human body.

Different subtypes of this virus have different 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 hyperproduction of proinflammatory 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, unlike the human virus, is more stable in the environment. At a temperature of 36 °C it dies in three hours, at 60 °C - in 30 minutes, and during heat treatment of food products (boiling, frying) - instantly. Tolerates freezing well. It survives in bird droppings for up to three months, in water at a temperature of 22 °C for four days, and at 0 °C for more than a month. Remains active in bird carcasses for up to a year. Inactivated by conventional disinfectants.

Epidemiology of avian influenza

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). Wild ducks are of greatest importance. Influenza viruses in Eurasia and America evolve independently, so migration between continents does not play a role in the spread of the virus; flights in longitude are decisive. For Russia, the Central Asian–Indian and East Asian–Australian migration routes are important in this regard. These include routes going to Siberia via Malaysia, Hong Kong and China, i.e. regions where new variants of the virus are intensively forming. Less significant are the East African-European and West Pacific routes.

In wild waterfowl, the virus does not cause clinically significant disease, although a large-scale severe epizootopy of influenza has been described in Arctic terns. Replication of the virus in birds occurs primarily in the intestines and, accordingly, it is released into the environment with feces, and, to a lesser extent, with saliva and respiratory material. 1 g of feces contains enough virus to infect 1 million poultry.

Main mechanism of virus transmission in birds- fecal-oral.

Waterfowl (ducks) are capable of transmitting the virus transovarially and, thus, serve as its natural reservoir and spread it along their migration routes. They act as 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 keeping and the possibility of contact with their wild counterparts. This is especially typical for the countries of Southeast Asia (China, Hong Kong, Thailand, Vietnam and other countries). There, along with large poultry farms, there are many small peasant farms.

The avian influenza virus can infect mammals: seals, whales, minks, horses and, most importantly, pigs. Cases of the virus entering the population of the latter were noted in 1970, 1976, 1996 and 2004. These animals can also be affected by the human influenza virus. Currently, human susceptibility to similar avian viruses is low. All cases of infection were recorded in those who had long-term and close contact with a sick bird. An experiment carried out in the UK to inject various subtypes of the virus into the body of volunteers gave a negative result.

In Thailand, where the population is 60 million people, during an epizootic that affected two million birds, 12 cases of the disease in humans were reliably identified. In total, by 2007, about 300 episodes of avian influenza in humans were registered. Two cases of infection from a sick person have been officially recorded.

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

Even isolated cases of human infection from birds and from patients indicate that the insurmountability of the interspecies 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, may be many times higher. During the H7N7 influenza epizootic in Holland, 77 people fell ill and one died. High titers of antibodies were found in persons in contact with patients, 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 the avian influenza virus, especially the H5N1 subtype, is very high.

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

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.

Fourthly, genetic methods have proven that the Spanish flu pandemic of 1918–1919. was of "bird" origin.

Fifthly, in modern conditions, thanks to the processes of globalization and the availability of fast modes of transport, the possibility of spreading the assorted virus increases sharply. Thus, it is fair to conclude that the likelihood of a new variant of the influenza A virus emerging and causing a severe pandemic is very high.

Using mathematical modeling methods, it is 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, the rapid culling of birds during an epidemic in Hong Kong in 1997 may have prevented an influenza pandemic. US experts predict that in the event of a pandemic in America, from 314 to 734 thousand people will need to be hospitalized, and from 89 to 207 thousand will die.

Pathogenesis of avian influenza in humans

Currently, the mechanism of development of influenza caused by the H5N1 virus in humans has not been sufficiently studied. It has been established that the site of its replication is not only the 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 differ in their ability to recognize and bind to the receptor - sialic acid, bound in an oligosaccharide of cell membranes with galactose. Hemagglutinins of human influenza viruses interact with residues of this acid, united by a 2,6 bond with galactose, and hemagglutinin of avian influenza viruses recognizes it in a 2,3 bond with galactose residues. The type of terminal sialic acid bond and the conformational mobility of surface lectin oligosaccharides are the main elements of the interspecies barrier for avian and human influenza viruses. Lectins from human tracheal epithelial cells include lectins with a 2.6 linkage type and do not contain oligosaccharides with a 2.3 linkage type 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 emergence of its ability to overcome the interspecies barrier, can lead to damage to 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 catarrhal syndrome, gastrointestinal damage develops.

Clinical picture (symptoms) of avian influenza

The incubation period for influenza A (H5N1) is 2–3 days, ranging from 1 to 7 days.

Main symptoms and dynamics of their development

The onset of the disease is acute. Symptoms of intoxication are expressed. From the first hours of illness, body temperature rises to 38 °C, often reaching hyperpyretic values. The febrile period extends to 10–12 days, and in severe cases with a fatal outcome - until the last hours of the patient’s life. Characterized by chills, muscle and joint pain. At the height of the disease (2–3 days), catarrhal syndrome occurs, manifested by the development of bronchitis, bronchiolitis, and laryngitis; There may be signs of rhinitis. Characterized by sore throat and “flaming” oropharyngitis. During this period, most patients develop primary viral pneumonia. In this case, shortness of breath and a wet cough with sputum, possibly mixed with blood, appear. Hard breathing, moist rales of various sizes, and crepitus are heard above the lungs.

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

In most patients, signs of damage to the nervous system are detected, disturbances of consciousness and the development of encephalitis are possible.

The hemogram records leukopenia, lymphopenia, and thrombocytopenia.

There may be variants of the course of the disease with fever, diarrhea and no signs of respiratory damage.

Complications of bird flu

The infection is dangerous due to the development of viral pneumonia, damage to the kidneys, liver, and hematopoietic 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 influenza virus in people (at least in those who died as a result of the disease) is not only the respiratory tract, but also the intestines.

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

Age of the patient (in children five years and younger, the symptoms of the disease are not clearly expressed);
- duration of manifestation of the disease before hospitalization (delay from hospitalization);
- anatomical level of damage to the respiratory tract;
- degree of peripheral blood leukopenia;
- presence of multiple organ dysfunction.

Mortality and causes of death

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

Diagnosis of bird flu

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

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

The presence of reports of outbreaks of influenza A (H5N1) among the population of birds and animals or cases of death of poultry in the region of residence of the patient;
- contact with a sick person confirmed to be infected with the influenza virus (H5N1), seven days before the appearance of the first clinical signs;
- contact with a patient with an acute respiratory infection of unknown etiology, including one that ended in death, seven days before the appearance of the first clinical signs;
- instructions for the patient to travel to a country or territory where there are reports of an unfavorable epidemiological and/or epizootic situation regarding influenza A (H5N1);
- presence of an occupational risk of infection of the patient;
- high fever combined with difficulty breathing, cough;
- diarrhea (in the absence of blood in the feces).

The final diagnosis can be made after laboratory confirmation.

Laboratory diagnosis is based on the methods of virological research, serological reactions, immunofluorescence analysis and PCR.

Differential diagnosis

Considering that influenza A (H5N1) causes symptoms of respiratory tract damage, it is necessary to carry out differential diagnosis with other acute respiratory viral infections: “traditional” influenza (A, B), severe acute respiratory syndrome, parainfluenza, respiratory syncytial, adenoviral and enteroviral infections, and also legionellosis and ornithosis.

Indications for consultation with other specialists

If ARF develops, consult a resuscitator.

An example of a diagnosis formulation

J10. Influenza caused by the H5N1 virus, severe; complication - pneumonia, ARF.

Indications for hospitalization

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

Treatment of bird flu

Mode. Diet

If the diagnosis of influenza A (H5N1) is confirmed, treatment is carried out in a hospital ward. During the entire acute period of the disease, bed rest must be observed. A nutritious diet rich in vitamins and containing sufficient fluid is recommended.

Drug therapy

Etiotropic therapy

Currently, the most effective etiotropic drug is oseltamivir (Tamiflu), an antiviral drug belonging to the class of neuraminidase inhibitors. It is prescribed at a dose of 75 mg orally twice a day for seven days. It is possible to increase the dose to 300 mg. You can also use rimantadine (rimantadine, algirem).

Pathogenetic agents

In pathogenetic therapy, the leading role belongs to detoxification. 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 and aprotinins are indicated. With the development of ARDS, treatment is carried out in an intensive care unit with mandatory respiratory support, and surfactant is administered. Symptomatic therapy is carried out according to indications.

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

All those in contact with patients with influenza A (H5,N1) are given medical observation for seven days, with body temperature measured twice a day. If it increases, coughing and difficulty breathing appear, you should immediately seek medical help.

Forecast

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

Prevention measures

Specific

Global monitoring under the auspices of WHO makes it possible to quickly detect a dangerous virus and begin mass production of a vaccine. Mass vaccination could begin in nine months. Currently, it is important to carry out high-quality anti-epidemic measures aimed at reducing the prevalence of human influenza. In particular, it is necessary to increase the number of vaccinated people, which will reduce the incidence rate, and possibly susceptibility to the new variant of the virus. Some countries produce limited quantities of vaccine against antigenic variants of the virus. According to forecasts, they are the most likely candidates for the new pandemic virus.

The main method of combating avian influenza is the complete extermination of the bird population on infected farms, and persons in contact with them and carrying out their destruction must work in respirators and special clothing. Great importance is attached to disinfection using quaternary ammonium compounds (acepur), which are non-toxic to humans. They are easily neutralized by soaps and other detergents. They carry out quarantine measures and prohibit the export of poultry and eggs from the affected regions. Vaccination is carried out on surrounding farms and poultry farms, but its effectiveness and feasibility are questionable. The presence of antibodies in vaccinated birds makes monitoring difficult, as it does not allow differentiation from infection; there is also evidence that vaccination contributes to mutation of the virus.

The introduction of infection into Russia is possible with migratory birds. However, the conditions of farming in Russia (predominantly closed poultry keeping, low probability of contact with pigs, less close contact between people and animals than in Southeast Asia) make it possible to practically exclude the possibility of the emergence of an assortment virus. In this regard, the main measures should be aimed at preventing the transmission of the virus from countries where it may appear. To do this, sanitary control at the border should be tightened and the wearing of respiratory masks should be recommended; their preventive effectiveness reaches 98%.