The symptoms of avian influenza vary with the species, age, sex, degree of concurrent infection, virus virulence and environmental factors of infected birds, mainly manifested as abnormalities in respiratory tract, digestive tract, reproductive system or nervous system.
Common symptoms are: listlessness, reduced feed consumption and emaciation of sick chickens; The nesting ability of hens is enhanced and the egg production is reduced; Mild to severe respiratory symptoms, including coughing, sneezing and profuse tears; Head and face edema, nervous disorder, diarrhea.
Any of these symptoms may appear alone or in different combinations. Sometimes the disease breaks out quickly and the chicken is found dead without obvious symptoms.
In addition, the incidence and mortality of avian influenza vary greatly, depending on the variety and strain of poultry, age, environment and concurrent infection. Usually, the incidence is high and the mortality is low. In the case of highly pathogenic virus infection, the morbidity and mortality can reach 100%.
The incubation period of avian influenza varies from several hours to several days, and its length is related to the pathogenicity of the virus, the dose of the virus infected, the route of infection and the species of infected birds.
Avian influenza is short for avian influenza. Up to now, there are 15 subtypes of influenza A virus hemagglutinin (H1-5) and 9 subtypes of neuraminidase (N 1-9), all of which can be found in birds. So far, domestic ducks, wild ducks, domestic chickens, pheasants, turkeys, guinea fowl, seagulls, terns, geese, swans, quails, pigeons, sparrows, starlings, crows, emus, emus and grey herons have been isolated from poultry.
The symptoms of avian influenza in chickens, ducks and other poultry are diverse, mainly manifested as abnormalities in respiratory tract, digestive tract, reproductive system or nervous system, such as: sick chickens are often depressed, feed consumption is reduced, and hens' egg production is reduced; Before dying, sick birds will have symptoms of central nervous system and systemic poisoning, such as extreme emaciation, diarrhea and dysentery, body curl and convulsions.
Poultry experts say that the incubation period of avian influenza varies greatly, some are hours, some are days, and its length is related to the pathogenicity of the virus, the amount of virus infected, the route of infection and the types of infected poultry. When infected with highly pathogenic virus, the morbidity and mortality of poultry can reach 100%. The outbreak of H5N 1 influenza virus was unexpected. Poultry often has no abnormal symptoms before the incident and soon dies in large numbers.
Human diseases are similar to influenza.
The symptoms of human infection with avian influenza are different from those of birds. According to Guo Yuanji, a researcher at the National Influenza Center of China Center for Disease Control and Prevention, the symptoms of human infection with avian influenza are very similar to those of human influenza, and it is quite difficult to identify them clinically. The incubation period of patients is usually less than 7 days. The main symptoms in the early stage are fever, runny nose, stuffy nose, cough, sore throat, headache and general malaise. Some patients have digestive tract symptoms such as nausea, abdominal pain and watery stool, and some patients will be complicated with conjunctivitis. The body temperature of most patients continues to be above 39 degrees Celsius. After the disease develops, some patients will have unilateral or bilateral pneumonia, and a few patients will be accompanied by pleural effusion. A small number of patients can aggravate their illness, develop into progressive pneumonia, acute respiratory distress syndrome, pulmonary hemorrhage, pleural effusion, renal failure, septic shock and other complications and die. Guo Yuanji said that in recent years, bird flu has been regarded as a new acute infectious disease in the world, and it has been listed as one of the contents of international anti-bioterrorism, because there have been human cases and showed a high mortality rate.
Up to now, cases of human infection with avian influenza have been confirmed by H5N 1, H7N7 and H9N2 subtypes. Guo Yuanji believes that while being highly alert to H5N 1 virus, we should also pay attention to the threat from H9N2 subtype avian influenza virus strain. This virus has similar receptor specificity to human influenza virus, and it has a certain infection range in the population, but it is mostly inconspicuous infection in poultry and is not easy to be detected by people.
How to prevent avian influenza
On February 2, a spokesman for the World Health Organization made it clear that the organization did not intend to raise the early warning level of bird flu in view of the fact that the global bird flu has not spread rapidly to people. In view of the fact that prevention of avian influenza is more important than treatment, health experts put forward some suggestions on how to avoid contracting avian influenza.
The first is not to touch live birds. Highly pathogenic avian influenza virus can survive for a long time under certain conditions. It can survive in bird droppings for 105 days and in feathers for 18 days, so people who come into contact with sick birds are much more likely to be infected. Experts suggest that contact with poultry, eggs and raw and cold poultry products should form the habit of washing hands, and wash hands thoroughly with hand sanitizer and water, especially children should avoid contact with live birds.
Because avian influenza virus is sensitive to commonly used disinfectants such as caustic soda, aldehydes, oxidants, chlorine preparations and biquaternary ammonium salts, it is necessary to disinfect the working and living environment frequently. Keep floors, ceilings, furniture and walls clean; Ensure that the drainage channel is unobstructed; Use washable floor mats to avoid using carpets that are inconvenient to clean; Bird breeders should strengthen the disinfection of bird cages in pigeon houses. In addition, high temperature and ultraviolet rays can kill avian influenza virus, and 60 degrees Celsius 10 minutes, 100 degrees Celsius and long-term sunlight can kill avian influenza virus. Therefore, it is necessary to maintain adequate ventilation and sunshine indoors.
At present, there is no avian influenza vaccine for human use, and the high incidence of respiratory diseases is in winter and spring, so people should strengthen exercise, have more rest, improve immunity, pay attention to personal hygiene, go to places with poor air circulation as little as possible, and cover their nose and mouth when sneezing or coughing. In case of unexplained pneumonia, bird flu must be investigated.
Experts also particularly stressed that it is necessary to change the buying and eating habits, buy quarantined and packaged poultry meat from regular shops and commercial outlets, and do not slaughter poultry yourself at present. When eating chicken, goose, duck and other poultry meat, be sure to cook it before eating, and be sure to separate raw and cooked in the kitchen. Do not eat raw animal blood products.
In view of the fact that it is not clear whether there is virus in egg yolk and egg white, it is suggested that egg white and egg yolk should not be used as masks for the time being for safety reasons.
In addition, down jackets, duvets, etc. Will not be infected with bird flu. Because down products are usually treated by disinfection and high temperature, viruses are unlikely to survive and do harm to people's health. But it is best not to buy cheap down products provided by small vendors. ▲
What is avian influenza?
The name bird flu may be a little strange to ordinary people. Because it was called chicken plague for a long time in the past, it was first reported in 1878 Italy. 190 1 year confirmed that the pathogen was a viral pathogen, and 1955 confirmed that the pathogen was a member of influenza A virus. Later, it was found that there were similar diseases in birds, called Newcastle disease. The two are often confused.
In order to distinguish the two, the former is called avian influenza or true chicken plague, European chicken plague, and the latter is called Newcastle disease or pseudo chicken plague and Asian chicken plague. Therefore, avian influenza is an acute infectious disease caused by influenza A virus.
According to different pathogenicity, avian influenza viruses can be divided into three categories: high pathogenicity, low pathogenicity and non-pathogenicity. Highly pathogenic avian influenza has been listed as a kind of animal disease by the World Organization for Animal Health because of its rapid spread and great harm, and it is listed as a kind of animal disease in China.
2. What is the relationship between avian influenza virus and influenza virus?
What we usually call influenza is an acute respiratory infectious disease caused by influenza A (A), B (B) and C (C) viruses. Type A and B, especially type A, can cause human influenza epidemic, while type C only causes sporadic cases. Avian influenza is caused by influenza A virus.
Influenza A virus has two surface antigens, hemagglutinin (H) and neuraminidase (N), which can be further subdivided. H can be divided into H 1 ~ H 15, and n can be divided into N 1 ~ N9. Different hemagglutinins and different neuraminidase will form influenza viruses with different antigenicity and pathogenicity, which are called influenza virus subtypes in technical terms.
There are 145 subtypes of influenza A virus, among which H 1 ~ H3 is the main type that can cause human influenza, and H 1N 1, H2N2 and H3N2 have caused human influenza epidemic. The natural hosts of most other subtypes are birds, pigs, horses and other animals, especially waterfowl. All antigens of H 1 ~ H 15 and N 1 ~ N9 subtypes can be isolated from animals.
3. What factors determine whether influenza will become an epidemic?
The biggest feature of influenza virus is antigen variability, which can cause changes in transmission. Among them, type A antigen has the strongest variability, and small variation often occurs, which is called "antigen drift". The degree of influenza virus variation is different, and the degree of epidemic is also different. When the influenza virus has a large variation or subtype transformation, it is called "antigen transfer", which may cause a worldwide influenza epidemic. Comparatively speaking, the variability of type B is weak, which will only cause outbreaks and epidemics in local areas; Type C is relatively stable and only causes sporadic cases. Therefore, influenza A virus is the focus of human research, prevention and control.
4. What is the drug resistance of avian influenza virus?
Avian influenza virus can survive for several months to more than one year in low temperature, dryness and glycerol. In dry dust, the virus can survive for 14 days. At low temperature, the virus survived in contaminated feces for at least 3 months. In water, it can survive for 4 days at 22℃ and for more than 30 days at 0℃. It can survive in frozen poultry meat and bone marrow for 10 month. Avian influenza virus is afraid of sunlight, heat and common disinfectants. Under direct sunlight, it can be inactivated in 40-48 hours. The virus can be killed by heating (60℃ for 30min, 100℃ 1 min) or common disinfectants (formalin, complex iodine, etc.). ).
5. Why is human avian influenza a new infectious disease?
Although bird flu has been prevalent in birds and other animals for more than 100 years, there has never been a report of human infection before. During the period of 1997, there were 18 cases of avian influenza in Hong Kong, among which 6 people died. The virus strains of this human avian influenza epidemic are consistent with those of Hong Kong poultry at that time, both of which are H5N 1 type. This is the first time that bird flu has infected humans. Therefore, avian influenza is a newly discovered infectious disease.
Transmission characteristics of avian influenza
6. What is the source of infection of avian influenza?
The source of infection refers to animals and people who have pathogens living and reproducing in their bodies and can excrete pathogens. The main sources of infection of avian influenza are sick birds and infected birds, including waterfowl and flying birds. Studies have shown that for highly pathogenic avian influenza, the virus content in 1 g contaminated feces can cause 1 10,000 birds to be infected. At present, people cannot be considered as the source of infection of avian influenza.
7. What are the susceptible animals of avian influenza?
Animals that are infectious to infectious diseases are called susceptible animals. Chickens, turkeys, ducks, geese, quails, pheasants, partridges, ostriches, pigeons and peacocks are all susceptible to avian influenza. Chickens and turkeys are the most sensitive, and waterfowl such as ducks and geese are mostly recessive infections. Co-raising waterfowl and dry birds in the same site will cause cross-infection, and the virus can easily spread between chickens or ducks raised on a large scale. Wild and farmed waterfowl can spread in the same water body by using * * *.
Besides infecting birds, bird flu can also infect pigs.
8. How does bird flu spread among birds?
Avian influenza is mainly transmitted through contact with infected birds and their secretions and excretions, contaminated feed, water, egg plates (boxes), padding, eggs, chicken embryos and semen. , through respiratory and digestive tract infections, but also through air-borne media.
In nature, birds carry the widest range of viruses, so migratory birds, wild birds and waterfowl with a wide range of migration play an important role in the spread of diseases. It is not clear whether the parasitic insects on the surface of poultry are also toxic, and biting people can also be infected.
9. How did the avian influenza virus spread to humans?
Avian influenza virus can enter the human body through the digestive tract and respiratory tract and infect people. If you come into direct contact with articles with a considerable amount of viruses, such as poultry droppings, feathers, respiratory secretions, blood, etc. It can also cause infection through conjunctiva and broken skin.
10. Who are the high-risk groups of avian influenza?
Veterinarians and people who have been engaged in raising, selling and slaughtering chickens, ducks, geese and pigs for a long time.
1 1. Will bird flu spread from person to person?
At present, only human-to-human cases transmitted by poultry have been found, and no human-to-human cases have been found. In other words, there is no evidence that people can infect each other. However, WHO warns that theoretically, if the virus mutates, it may spread from person to person.
12. How is bird flu spread in some areas?
Bird flu can easily spread from one farm to another. Bird droppings can contain a large number of viruses, causing dust and soil pollution, and then spread among birds through the air. The virus spreads from one farm to another by polluting equipment, means of transport, feed, cages, clothes and especially shoes. Viruses can also spread through the feet and bodies of animals (such as rodents). Live birds are traded in crowded markets, and the sanitary conditions are poor, which is also a mode of transmission. At present, the ability of flies to spread this virus has not been confirmed.
13. How does bird flu spread over a long distance?
Bird flu can spread from one country to another through the international trade of live birds. Migratory birds, including wild waterfowl, seabirds and shorebirds, can carry viruses over long distances. Wild ducks are the most striking natural hosts of avian influenza virus, and they have strong resistance to virus infection, sometimes with mild and non-fatal symptoms, but they can carry the virus from a long distance and excrete the virus through feces. People raise ducks, turkeys, geese and other poultry for commercial and domestic use, which will lead to fatal infections. Free movement of poultry, use of water with wild birds or use of water contaminated by feces of infected wild birds are the most dangerous.
14. Will eating cooked poultry and eggs get infected?
The main route of human infection with avian influenza virus is contact infection. After the poultry meat is cooked, the virus can be killed and the possibility of transmission is very small. At present, no cases of infection caused by eating poultry meat and eggs have been found. However, if sick birds are not cooked and eaten thoroughly, the virus may enter the human body. Therefore, if you eat poultry that have not been quarantined or come from epidemic areas, you will not rule out the risk of illness.
15. Is it contagious to buy live chickens home?
If it is a healthy live chicken, it is basically safe. If it is a sick chicken, it is dangerous. WHO warns that no matter what kind of sick chickens people come into contact with, they are equally dangerous. A few infected poultry can survive, but they will excrete virus-containing feces for at least 10 days. In addition, the chicken wings may contain avian influenza virus, so the virus may be released when the chicken wings flap.
16. Will down products spread avian influenza?
Down products are usually treated by disinfection and high temperature, so the probability of spreading the virus should be very small.
Clinical manifestations of avian influenza
17. How long is the incubation period of avian influenza?
The incubation period refers to the period from the invasion of pathogens into the body to the appearance of initial symptoms. The incubation period of avian influenza in poultry ranges from several hours to several days, and the longest incubation period can reach 2 1 day. After human infection with avian influenza, the incubation period usually does not exceed 7 days.
18. What are the manifestations of avian influenza infection in poultry?
There are two forms of post-infection diseases in poultry:
Low-pathogenic avian influenza only causes mild symptoms, and sometimes it only manifests as wrinkled feathers, disorder and decreased egg production.
Birds suffering from highly pathogenic avian influenza can suddenly die, with high mortality rate, and the consumption of feed and drinking water and the amount of eggs dropped sharply. Sick chickens are extremely depressed, head and face edema, cockscomb cyanosis, foot scale bleeding and nervous disorder. Waterfowl such as ducks and geese have obvious neurological and diarrhea symptoms, which can cause corneal inflammation and even blindness.
Once the above symptoms are found in poultry farms, it can be suspected to be highly pathogenic avian influenza.
19. What are the symptoms of human suffering from avian influenza?
After human suffering from avian influenza, the early symptoms are very similar to severe influenza, such as high fever, runny nose, stuffy nose, cough, sore throat, headache and general malaise. Some patients may have digestive tract symptoms, such as nausea, abdominal pain, diarrhea and watery stools. Some patients can see eye infections such as conjunctivitis, and most patients' body temperature is above 39℃. Some patients will have unilateral or bilateral pneumonia on chest radiograph, and a few patients will have pleural effusion. Some patients may develop acute respiratory distress syndrome and other serious life-threatening syndromes. The mortality rate of human suffering from avian influenza is as high as over 30%.
Diagnosis and treatment of avian influenza
20. How to diagnose poultry avian influenza in the laboratory?
When collecting live poultry samples, cloacal swabs and tracheal swabs can be used for sampling. When collecting dead bird samples, tissues and organs such as trachea, spleen, lung, liver, kidney and brain should be collected. For small rare birds, fresh feces should be collected.
Laboratory examination includes etiological diagnosis and serological examination. Etiological examination includes pathogen isolation, gene identification and virulence determination. Serological diagnosis mainly includes agar gel immunodiffusion test (not suitable for waterfowl) and hemagglutination inhibition test (H 1).
2 1. How to confirm avian influenza in poultry?
According to the Emergency Notice on Strengthening the Prevention and Control of Highly Pathogenic Avian Influenza issued by the Ministry of Agriculture on June 28, 2004, the epidemic situation of highly pathogenic avian influenza in China was confirmed according to the following procedures:
① After receiving the epidemic report, the provincial animal husbandry and veterinary department sent more than 2 avian influenza experts to the scene for clinical diagnosis. If the clinical symptoms are obvious, it can be suspected that it is a highly pathogenic avian influenza epidemic.
② When the epidemic situation of highly pathogenic avian influenza is suspected, collect samples in time and send them to provincial laboratories for serological testing. If the diagnosis result is positive, it can be identified as a suspected case of highly pathogenic avian influenza.
③ Suspected cases should be sent to the National Avian Influenza Reference Laboratory for further identification, and specimens should not be mailed.
4. The National Avian Influenza Reference Laboratory shall conduct pathogen isolation and identification on the disease materials reported by all provinces, autonomous regions and municipalities directly under the Central Government, and report the conclusion to the Ministry of Agriculture.
22. What is the diagnostic basis of human avian influenza?
The diagnostic principle of human avian influenza is comprehensive analysis and diagnosis based on epidemiology, clinical symptoms and laboratory examination. Referring to the Diagnostic Criteria and Prevention Guidelines for New and Recurrent Infectious Diseases edited by Enshi, the diagnosis basis is as follows:
(1) Epidemiological history: Avian influenza occurred before, that is, a large number of birds (chickens, ducks, geese, etc.) appeared in a poultry farm. ) developed bird flu-like symptoms in a certain area and died; There is an epidemic or outbreak of avian influenza in the vicinity or surrounding areas.
② Clinical manifestations include sudden onset, fever (above 38℃), cough, sore throat, headache, dizziness, general aches, fatigue and other poisoning symptoms, accompanied by respiratory symptoms such as dry cough, runny nose and tears. A few cases have anorexia, accompanied by gastrointestinal symptoms such as abdominal pain, abdominal distension and vomiting.
③ Laboratory examination isolated influenza virus from nasopharyngeal or tracheal secretions of patients; The titer of anti-influenza virus antibody in serum of convalescent patients is more than 4 times higher than that in acute stage. The specific protein components or specific nucleic acids of influenza virus particles were found in the respiratory epithelial cells of patients; After the virus was propagated by sensitive cells for one generation, the specific protein or specific nucleic acid of influenza virus particles was found.
At present, there is no unified standard for the classification of human avian influenza cases in China, and the Ministry of Health is organizing the formulation.
23. Do birds need treatment after being infected with avian influenza?
At present, there is no reliable treatment for avian influenza. After birds are infected with avian influenza, they must be thoroughly culled to prevent the spread of the epidemic.
24. What do you think of human infection with avian influenza?
① General treatment should be based on respiratory isolation 1 week or until the main symptoms disappear. Patients need to stay in bed, drink plenty of water, have proper nutrition, supplement multivitamins and keep their nasopharynx and mouth clean. Those with severe symptoms should be hospitalized. Antibiotics are only used when bacterial complications occur.
② Patients with high fever and headache can be treated with physical cooling or antipyretic sedatives, and aspirin is forbidden in children. Patients with high fever and vomiting should be given intravenous rehydration. People who cough and expectorate can take antitussive and expectorant drugs.
③ Take amantadine and rimantadine, anti-influenza drugs. Amantadine and rimantadine are inhibitors of virus M2 protein, which are effective for influenza A, blocking the virus's adsorption to sensitive cells. Usually taking medicine within 48 hours of onset can reduce the amount of virus discharged, shorten the time of detoxification, relieve clinical symptoms, reduce fever within one or two days, prevent infection from spreading to the lower respiratory tract and reduce the occurrence of pneumonia. Za-Nimivir and oseltamivir are neuraminidase inhibitors, which can resist influenza A and B viruses.
25. Can people get bird flu and be cured?
Most patients can be cured after timely treatment. Short course of disease, quick recovery and no sequelae. A few patients, especially those who are older and treated too late, develop rapidly, and patients may die of various complications such as progressive pneumonia, acute respiratory distress syndrome, pulmonary hemorrhage, pleural effusion, pancytopenia, renal failure, sepsis and shock. Therefore, once the patient has the above symptoms, he should seek medical attention in time. Once you are suspected of being infected with H5N 1 virus, you should be hospitalized immediately for isolation treatment and report the epidemic situation to prevent the disease from getting worse and spreading.
Avian influenza infection
Bird flu can infect many kinds of animals, including birds, pigs, horses, seals, whales and humans. However, as asymptomatic carriers, wild birds spread them to more susceptible poultry. It is mainly transmitted in birds through respiratory tract and feces, and there is no evidence that the virus can survive in cooked meat. Viruses first infect the digestive tract of birds, they replicate in the epithelial cells of the small intestine, and finally spread with feces. The symptoms of bird flu infection in animals vary greatly, but the highly virulent type may die within a few days.
The symptoms of avian influenza are similar to those of other influenza, such as fever, cough, sore throat, muscle soreness and conjunctivitis. In severe cases, respiratory problems and pneumonia may be life-threatening. There are also some atypical symptoms. In one case, a boy infected with H5N 1 virus developed diarrhea.
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The source and spread of avian influenza
In the early period of 1900, avian influenza was first confirmed in Italy. In 960, more than 65,438+0,000 common terns died in South Africa. This is the first case of high mortality caused by avian influenza, belonging to H5N3 type.
According to the technical document H5N 1 issued by the Working Group on the Convention on Migratory Species of the United Nations Environment Programme, the source of subtype avian influenza comes from centralized poultry, and the extreme feeding environment leads to the variation of the virus. Human activities such as bird trade, vaccine abuse and transportation have also promoted the variation of avian influenza virus. Field research shows that the vast majority of wild birds suffering from avian influenza are species that have had close contact with poultry raised by human beings during migration, wintering and reproduction, while those wild birds, even waterfowl, which are far away from human society from beginning to end and maintain a high population density have not yet reported the epidemic situation of avian influenza.
Viruses from farms infect wild birds, especially waterfowl, making the virus spread with bird migration. The outbreak of avian influenza in East Asia from the end of 2003 to the beginning of 2004 is considered to verify the hypothesis that migratory birds spread viruses: the epidemic first appeared in South Korea, where migratory birds stopped, then passed through Hong Kong and finally arrived in Vietnam. Due to the relatively good sanitation environment in Hong Kong and previous experience in dealing with epidemic diseases, the disease did not cause a large-scale outbreak in the local area. Vietnam, with a relatively poor sanitation environment, not only kills birds, but also affects human beings. By June 5438+0, 2004, nearly 20 people had died. However, ornithologists pointed out that according to the laws of Siberia-East Asia-bird migration Passage, migratory birds basically completed their migration from north to south as early as the end of June165438+early February 65438. Previous radio positioning and tracking research in Hong Kong also showed that there were almost no migratory birds in the dead of winter. It is also observed that the wintering ground of most waterfowl is located in the north of 20 degrees north latitude, and only white-browed ducks and needle-tailed ducks will migrate to Vietnam, but their transit time is 65438+early February. It is generally believed by ornithologists that the outbreak of avian influenza at the end of 2003 did not overlap with the migration of migratory birds in time and space, so most ornithologists disagree with the statement that migratory birds spread the virus.
It's not just migratory birds that are accused of spreading bird flu virus. According to the communiqué of the Third Meeting of the Parties to the Agreement on the Protection of Non-Eurasian Migratory Waterbirds on 27 October 2005, besides migratory birds, there are other ways to carry and spread avian influenza virus, such as livestock transportation, poultry and caged birds transportation, activities related to this industry, legal or illegal bird trade and human trafficking.
In poultry, once ducks and geese are infected, their disease resistance is relatively high, and the chances of survival after illness are also high. However, chickens are very sensitive to influenza virus. Once infected, it not only spreads quickly, but also the infected chicken will die soon. In the past, farmers generally referred to this phenomenon as "chicken plague" and did not pay special attention to the reasons behind it or the pathogenesis. It was not until the case that bird flu spread from animals to people and died that people began to pay attention to bird flu. At present, the main means for people to deal with avian influenza is to kill and bury infected and possibly infected poultry on a large scale, so as to avoid virus accumulation and further affect human beings.
In the bird flu epidemic in 2004 and 2005, some media also pointed out that the bird flu virus originated from wild birds, spread to farms and then passed on to humans. It is suggested to strengthen the monitoring of migratory birds' migration. A few activists even advocated culling migratory birds in addition to poultry, but this view was not recognized by ornithologists, and the proposal to cull migratory birds attracted opposition from environmental groups.
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Impact of avian influenza
The outbreak and epidemic of avian influenza will have many effects.
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Impact on the economy
Countries and regions where avian influenza broke out will cull poultry on a large scale near the epidemic spot for epidemic prevention reasons, which will have a serious impact on the aquaculture industry. The bird flu epidemic will also affect consumer confidence and hit the catering industry. Considering epidemic prevention, other countries and regions will suspend the import of poultry and products from epidemic areas, which will have an impact on the economy.
The governments of some countries and regions will block and conceal the occurrence of bird flu in their own countries only considering the huge impact of bird flu epidemic on the economy. However, this concealment of the epidemic situation often leads to poor epidemic prevention and further expansion of the epidemic situation. At the end of 2004, the Prime Minister of Thailand publicly apologized to the world for his government's concealment of the bird flu epidemic.
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Influence on human beings
Although the epidemic of avian influenza in June 5-38+February 2004 spread throughout many countries, only human cases were reported in Vietnam and Thailand. * * * 32 people were diagnosed in the laboratory and 22 people died, with a mortality rate as high as 70%. Although there are very few cases, in view of the serious epidemic situation of Spanish influenza in 19 18, whether avian influenza is zoonotic has always attracted much attention. At present, H5N 1 influenza virus has not been recombined with human influenza virus, and there is not enough evidence to prove human-to-human transmission, which is unlikely to cause mass death.
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Impact on the ecological environment
Avian influenza virus can infect wild birds, especially waterfowl. Many waterfowl will flock in groups during migration, wintering and during the period, with high population density, and the virus is easy to spread, causing serious harm. According to the report of the United Nations Environment Programme, 36 kinds of precious wild birds, including the spotted goose, the small white goose, the oriental stork and the white crane, are threatened by avian influenza. It is estimated that in the summer of 2005, more than110 wild geese died in the world. Because bird flu virus can spread among birds, and some birds have relatively concentrated habitats, the impact of bird flu epidemic on some birds may be disastrous.
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Prevention and control of avian influenza
To control infectious diseases, we should start with three links: the source of infection, the route of transmission and the susceptible population.
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source of infection
To prevent avian influenza, we must first start from the source of infection. Relevant reports pointed out that extreme poultry breeding environment is an important factor to promote the mutation of avian influenza virus, so improving poultry breeding environment and reducing the breeding density of farms are the fundamental means to prevent the mutation of avian influenza virus and the outbreak of epidemic diseases in the long run. In addition, keeping different kinds of poultry separately can also help to control the spread of epidemic diseases: keeping ducks, geese and chickens separately can prevent chickens from being infected with ducks and geese and dying in large numbers.
At present, vaccination for poultry has been proved to be the fastest and most effective way to control avian influenza. However, some experts in Hong Kong said that there is a certain risk in the current method of vaccinating all poultry in China mainland farms, that is, all poultry are vaccinated, so that all poultry have disease resistance. In this way, once bird flu breaks out again, all birds have the ability to resist disease, so farmers can't find it early and send an early warning to the relevant departments. At present, the practice in Hong Kong is to require all farms to keep a small number of birds that have not been vaccinated. In this way, once the bird flu comes again, these unvaccinated birds can play an early warning role and remind other farms to pay attention to the virus coming again. In addition, according to the work report of the United Nations Environment Programme, vaccine abuse is also an important factor inducing the variation of influenza virus, so over-injection of vaccine is not worth advocating.
The guiding principles of poultry culling issued by the World Organization for Animal Health on June 29th, 2005 mainly include the following aspects: poultry culling should be carried out under the guidance of professional veterinary experts, and personnel's biological protection should ensure animal welfare.
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Transmission routing
Migratory birds are important spreaders of avian influenza virus, but it is impossible to slaughter all infected migratory birds. The culling of migratory birds will disperse the originally gathered birds, making the spread of the virus more difficult to control. Therefore, isolating poultry from migratory birds and avoiding cross-infection are effective means to control the spread of avian influenza. In China, many farms hang giant nets in poultry farms to prevent virus-carrying migratory birds from infecting poultry. In addition, some European countries require farms to move birds indoors in order to cut off the contact between poultry and wild birds from the transmission route. Although moving poultry indoors will reduce their activity space, thus affecting the texture of poultry meat, it is also less than the loss caused by the need to eliminate all birds because of bird diseases.
In addition to bird migration, the global bird trade is also an important route for the spread of avian influenza virus. Legal bird fairs carry out strict animal epidemic prevention inspection in accordance with relevant laws and regulations, and the probability of spreading diseases is relatively small. The illegal bird trade, especially the smuggling of wild birds, is not within the monitoring scope of animal epidemic prevention. Capturing, selling, selling, eating and releasing wild birds will not only cause the virus to spread across regions, but also cause the virus to spread among birds due to the close contact between operators and wild birds. Therefore, strict monitoring of legal and illegal bird trade is also an important link to prevent and control the spread of avian influenza.
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susceptible population
On the human side, we should always keep farms and poultry farms clean and hygienic to avoid the accumulation of viruses. In addition, according to Dr. Jeremy Faller's clinical experience in Hanoi, Vietnam, people with active autoimmune systems,