Bird flu

The bird flu was first described by the Italian veterinarian in 1878 under the name of chicken fever . Perronchito reported an outbreak of highly contagious disease affecting chickens on farms in the vicinity of Turin ( Italy ).

For some time the bird flu was confused with Newcastle’s disease , but after the etiology was established, the latter was called pseudo - plague or Asian plague of birds , and bird flu was called classical or European bird plague .

Outbreaks of European bird plague occurred regularly at the beginning of the 20th century in Europe, Africa and Asia. In 1925, the disease hit North America. In the second half of the 20th century, only 18 major epizootics were recorded abroad.

In 1901, the viral nature of the pathogen was established, but it was only in 1955 that the virus causing the "bird plague" was proved to be a flu virus .

The modern name - avian influenza - the disease received only in 1971. In relation to the most dangerous forms (for example, caused by the H5N1 strain ), the term highly pathogenic avian influenza is also used.

The causative agent of avian influenza - RNA - virus-containing Influenza virus A , belonging to the family Orthomyxoviridae , on the complement-binding antigen ( RNP ) is related to the virus of influenza A in humans and animals. The virion is characterized by polymorphism, the predominant spherical shape, size 60-180 nm . The virion has a lipoprotein sheath with spines radially located on it, which contains a folded RNP ring. The virion genome consists of 6 or more types of RNA. The virus has infectious, hemagglutinating and neuraminidase activity. It multiplies well in developing 10-11-day-old chicken embryos . Virus-containing allantoic fluid has the ability to agglutinate red blood cells of many species. When a virus is cultivated in tissue culture, many strains have a cytopathic effect and hemadsorbing properties. Avian influenza virus strains isolated from different bird species may differ in virulence , pathogenicity spectrum, and surface antigen structure (hemagglutinin and neuraminidase). The virus is rapidly inactivated by the action of a 3% solution of caustic soda and phenol , a 0.1% solution of formaldehyde . It is long kept at low temperatures and drying.

Sixteen variants of the hemagglutinin structure (HA1-16) and nine neuraminidase (NA1-9) are known in influenza A virus. It is the combination of these two glycoproteins that determine the virus subtype. Theoretically, 144 such combinations are possible, 86 of which are actually found in nature. For birds, the most pathogenic variants are H5 and H7.

H5N1

WHO believes that H5N1 avian influenza can develop into a worldwide pandemic if the virus undergoes recombination of genes with the human influenza virus , that is, acquires new properties (the ability to be transmitted from person to person, etc.). Restructuring can happen if the natural host H5N1, say a pig , serves as the so-called. a transmission link or a living environment in which a widely spread influenza type A subtype (for example, H1N1 , H1N2 , or H3N2 ) and a highly pathogenic influenza A subtype H5N1 can mix. This process would create a new type A contagious subtype of influenza that preserves the deadly nature of the H5N1 virus. There would be no congenital immunity against this new influenza subtype in humans.

H7N9

Cases of infection with the H7N9 flu were recorded in China in April 2013, 453 cases of human disease were recorded by this virus. Except for one case in Beijing, all other cases are registered in the eastern regions. ^[1] 175 people died of the flu. ^[2]

The avian influenza virus is isolated from all types of domestic birds, as well as from quails , pheasants , terns and petrel . All strains of the virus, irrespective of the species of animals affected by them, are capable of recombination in the process of reproduction in one system, as a result of which new antigenically modified subtypes of the virus are formed. In some cases, the strains isolated in poultry farms during the mass death of chickens, in the laboratory were non-virulent. The latter testifies to the role of additional stress in the disease of the bird flu: housing conditions, the presence of secondary infections, such as mycoplasmosis , etc. The source of the pathogen is sick and ill birds, with a large amount of active virus secreted and secreted. The mechanism of infection is airborne. The transmission factors of the virus are infected exchange containers (trays for carcasses and eggs), feed, commercial products (bird carcasses, eggs , feather ) obtained during the incubation period or from clinically sick birds. Wild birds ( pigeons , sparrows , jackdaws and ravens ), as well as rodents and cats can play a certain role in the spread of the disease. Avian influenza occurs in the form of enzootic and epizootic .

In 2014, a group of scientists led by Sunetra Gupta of the University of Oxford found that the most dangerous strains most often occur in birds that are short-lived. Moreover, contacts between species with different lifespans contribute to the "resurrection" of previously suppressed virulent strains. This is due to the fact that the composition of the virus population is updated more quickly and does not have time to develop and consolidate the immunity of populations to closely related strains of influenza, the presence of which prevents the development of an epizootic of avian influenza. Due to new approaches in breeding domestic ducks, they are no longer kept in closed ponds, and are given to contact with wild ducks. Due to the short lifespan of domestic ducks and the lack of immunity to closely related strains, this has been one of the causes of bird flu outbreaks in recent decades. ^[3]

The sick bird acquires intense immunity only against the homologous subtype of the virus.

The incubation period is from 20-30 hours to 2 days. The disease is manifested by a sharp decline in egg production, feed consumption, thirst, and oppression. A sick bird has ruffled feathers, and shortly before death, cyanosis of the crest and earrings. Chickens are standing with their heads down and eyes closed; their mucous membranes are hyperemic; nasal openings sealed with exudate . Breathing hoarse, rapid, body temperature 43-44 ° C. Diarrhea is also observed, the litter is colored brown-green, neurosis , convulsions , manege movements .

At autopsy, catarrhal and catarrhal- hemorrhagic lesions of the mucous membranes of the digestive tract and respiratory tract, subcutaneous edema in the region of the pharynx, larynx, neck, chest, legs, multiple point hemorrhages in the stomach , intestines , spleen , liver , kidneys and heart are detected .

The diagnosis is based on isolating the virus from fresh patmaterial (lungs, liver, brain, etc.), as well as fresh blood sera at different periods of the disease, and identifying it in serological reactions.

Human infection was first reported in Hong Kong in 1997 during an outbreak of influenza in poultry. 18 people got sick, 6 died. A virus strain, H5N1 , was detected, and it was established that the virus was transmitted from birds to humans. By August 2005, 112 human cases of avian influenza were recorded in Vietnam , Thailand , Cambodia , Indonesia , of which 64 are fatal; not established transmission of the virus from person to person. In an attempt to stop the spread of the virus, millions of poultry were destroyed or vaccinated . ^[four]

Flu pandemics caused by mutated viruses , against which people do not have immunity , occur 2-3 times in 100 years. The influenza pandemic of 1918–1919 (“ Spanish flu”, H1N1 strain ) claimed the lives of 40–50 million people. It is believed that the virus "Spaniard" arose as a result of recombination of the genes of avian influenza viruses and humans. In 1957-1958 the pandemic of the " Asian flu " caused by the H2N2 strain. In the 1968-1969 pandemic " Hong Kong flu " (H3N2).

According to the World Health Organization, from February 2003 to February 2008, out of 361 confirmed cases of human infection with the avian influenza virus, 227 were fatal.

The last death of a person from bird flu was recorded in 2014 in Canada.

WHO recommendations for personal protection against avian influenza ^[5] :

• Do not allow children to play with wild birds or sick poultry.
• Do not touch or kill dead or sick birds.
• If a dead bird is found dead, other people and animals should be restricted to it, if possible burn it (you should additionally contact the district veterinary station to combat animal diseases or another veterinary institution), while protecting the mouth and nose with a mask or respirator. and hands with gloves. After work, thoroughly wash your hands and face with soap and change your clothes.
• Do not eat raw or poorly cooked meat or poultry eggs.
• Meat or poultry eggs should be stored in the refrigerator separately from other foods.
• If a sick bird is found, urgently notify the local veterinarian .
• If after contact with a bird you have any acute respiratory (flu-like) disease, you should immediately consult a doctor.

Despite ongoing efforts to vaccinate poultry, especially in China, and the fact that authorities in many countries have destroyed tens of millions of poultry , the virus continues to develop a new geographical area. H5N1 has expanded its reach throughout Southeast Asia, China , penetrated into Indonesia , and now into Western Europe and some parts of Russia . In addition, avian flu diseases in wild and domestic birds have been identified in Turkey , Romania and Scandinavia . The main carrier (or vector) of infection is currently considered to be waterfowl (for example, different types of ducks). Particular danger lies in the fact that they make flights of thousands of kilometers , and among them are carriers of the H5N1 virus and not ill with them. Tens of thousands of waterfowl nestle annually in central (for example, Qinghai lake) and eastern regions of China and fly from these places in many directions.

In January 2009, according to the professor of virology Mohamed Ahmed Ali , tests confirmed that the new vaccine developed at the National Research Center of Egypt is effective against the H5N1 virus ^[6] .

In August 2018, Microgen together with the Institute of Experimental Medicine and the FSBI "Institute of Influenza them. A.A. Smorodintseva, with the support of WHO, have completed the development of an experimental live influenza vaccine (AIDS) against influenza virus A / 17 / Hong Kong / 2017/75108 (H7N9). Documents for conducting clinical trials of the new vaccine were transferred to the Ministry of Health . The start of vaccine research was scheduled for the end of 2018 ^[7] .

Research and development of a new vaccine against the pandemic virus continues in Russia , the United States , China, and other countries. In addition, the possibility of using drugs traditionally used for ordinary seasonal flu is being investigated for the treatment and prevention of the avian influenza virus. For example, in Russia, several drugs were tested in the framework of antiviral activity research on avian influenza. It was shown that the drug stably suppresses the replication of the H5N1 virus in cell culture and reduces the infectivity of viral offspring. ^[8] But in order to reduce the potentially catastrophic consequences of a pandemic, in addition to the accumulation of antiviral drugs and vaccines, additional measures need to be taken. Reducing the impact of a pandemic will require coordinated international efforts to quickly and effectively share health information about outbreaks. A high level of international cooperation will be required to rapidly spread effective antiviral therapies and to take public health measures to prevent the spread of the pandemic.

Many of the questions reflecting the nature of the new pandemic, if it arises, the scientists have no answer, only assumptions. We do not know to what extent the virus will be transmitted from person to person, nor how quickly it will geographically spread, nor how deadly it will be. But researchers suggest that it will be difficult without much effort to contain the outbreak at the point (or points) from where the epidemic will begin to spread. If this fails, the virus can spread throughout the world within a few months.

The need to contain the spread of a new pandemic will require that health authorities and local authorities quickly and strategically distribute the population to several million doses of antiviral drugs (for example, oseltamivir or zanamivir ), Tamiflu (however, the effectiveness of these drugs is doubtful ^{[9 ]} ). Many other health measures will have to be taken, for example, to temporarily limit the movement of the population. Research ^{[10] that} models the outbreak of the epidemic and the effectiveness of public health interventions continues.

• Spanish flu
• Swine flu
• Feline flu

• Gorbunova A.S., Pysina T.V. Influenza of animals. - M .: Kolos , 1973. - 232 p.
• Syurin V.N. , Osidze N.G. Avian influenza // Little-known infectious animal diseases / Comp. F. M. Orlov. - 2nd ed., Pererab. and add. - M .: Kolos , 1973. - 312 p.
• Ravilov A.Z. , Smetanin M. A. Influenza of farm animals . - M .: Agropromizdat , 1989. - 128 p. - ISBN 5-10-000660-9 .
• Avian influenza: The origin of infectious biocatastrophes / Ed. Acad. RAMS V.I. Pokrovsky . - 2nd ed., Ext. - SPb. : Rostock, 2012. - 304 + IV p. - (21st century epidemics). - 18 700 copies - ISBN 978-5-94668-108-7 .

• Avian influenza on the World Health Organization website
• Epidemiologist.ru
• Confirmed human-to-human transmission
• A bird flu pandemic will kill a third of humanity
• Pandemic "bird flu" is inevitable
• Dangerous trends in the fight against avian flu
• Avian influenza, avian influenza virus - detailed information about avian influenza: the history of the avian influenza virus, the symptoms and prevention of avian influenza H5N1.
• CIDRAP (University of Minnesota School of Medicine)
• US National Institute of Health
• ITAR-TASS (inaccessible link from 13-05-2013 [2239 days] - history )
• ScienceDaily.com
• "The Mystery of the" Spanish "flu" The results of deciphering the genetic structure of the killer virus put scientists in a dead end.
• "PANDEMIA" SPANKS "1918-1920 IN THE CONTEXT OF OTHER INFLUENZA PANDEMIA AND “BIRD FLU” Here is an attempt to explain the phenomenon of “ Spanish flu ” in the context of other influenza pandemics and investigated the scientific background of the possibility of its return in connection with influenza epizooties among birds .

  Spread of bird flu among people and birds. Google Maps KMZ ( KMZ tag file for Google Earth )