Knowledge and comprehensive understanding of avian influenza
According to the different pathogenicity of avian influenza, avian influenza can be divided into highly pathogenic avian influenza, low pathogenic avian influenza and non-pathogenic avian influenza. Recently, avian influenza caused by H5N1 serotype at home and abroad is called highly pathogenic avian influenza, with high morbidity and mortality and great harm.
Human avian influenza (hereinafter referred to as human avian influenza) is an acute respiratory infection caused by some subtypes of avian influenza A virus. In May 1997, a 3-year-old child in Hong Kong Special Administrative Region of China died of unexplained multiple organ failure. In August of the same year, it was identified as human influenza caused by avian influenza A virus H5N1 by the US Centers for Disease Control and Prevention and the World Health Organization (WHO) National Influenza Center in Rotterdam, the Netherlands. This was the first time in the world that avian influenza A virus H5N1 infected humans.
It is generally believed that human beings are not easily infected with avian influenza virus. Although people can be infected at any age, children under the age of 13 account for a high proportion of the infected cases, and their illness is serious.
The main sources of infection are chickens, ducks, geese and other poultry, especially chickens, who suffer from avian influenza or carry avian influenza virus; But it does not rule out the possibility that other birds will become the source of infection.
The route of transmission is mainly through respiratory tract, through close contact with infected birds and their secretions, excreta, water contaminated by virus, and direct contact with virus strains.
Susceptible people generally think that they are susceptible at any age, but the incidence of children under 12 years old is higher and the condition is more serious. People who are in close contact with poultry that died of unexplained illness or infected or suspected to be infected with avian influenza are high-risk groups.
Patients usually have an acute onset, and their early manifestations are similar to ordinary influenza. It is mainly fever, the body temperature is mostly above 39℃, and the heat course lasts for 1 ~ 7 days, usually 3 ~ 4 days, which may be accompanied by 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. Severe patients’ condition develops rapidly, and there may be pneumonia, acute respiratory distress syndrome, pulmonary hemorrhage, pleural effusion, pancytopenia, renal failure, sepsis, shock and other complications. Chest x-ray examination of patients can show unilateral or bilateral pneumonia, and a few patients can be accompanied by pleural effusion.
Avian influenza virus is sensitive to organic solvents such as ether, chloroform and acetone. Common disinfectants are easy to inactivate, such as oxidant, dilute acid, sodium dodecyl sulfate, halogen compounds (such as bleaching powder and iodine agent) can quickly destroy its infectivity.
Avian influenza virus is sensitive to heat and can be inactivated by heating at 65℃ for 30 minutes or boiling at 100℃ for more than 2 minutes. The virus can survive for one week in feces and one month in water, and it also has viability under the condition of pH<4.1. The virus has strong resistance to low temperature, and can keep vitality for more than one year under the protection of glycerol.
The virus can be inactivated in 40 ~ 48 hours under direct sunlight, and its infectivity can be quickly destroyed if it is directly irradiated with ultraviolet rays.
Experts remind that people who have been to the epidemic spot of avian influenza outbreak, or who have close contact with infected poultry and their secretions and excretions, or who are engaged in avian influenza virus laboratory staff, should go to the hospital for examination in time when similar cold symptoms occur during this period to rule out the possibility of avian influenza.
Clinically, we should pay attention to differential diagnosis with influenza, common cold, bacterial pneumonia, infectious atypical pneumonia (SARS), infectious mononucleosis, cytomegalovirus infection, chlamydia pneumonia, mycoplasma pneumonia, pneumonia epidemic hemorrhagic fever and other diseases.
Usually, you should pay attention to food hygiene, do not drink raw water, do not eat immature meat and eggs and other foods; Wash your hands frequently and develop good personal hygiene habits. Frequent hand washing is the most effective way to prevent all kinds of viruses, whether common influenza virus or H5N1 virus from invading. Ordinary medical alcohol cotton balls and disinfectant soap can effectively kill bacteria and viruses. Good hygiene habits are the most economical and effective way to prevent various diseases.
The main route of avian influenza virus transmission is through dead birds, sick birds and their excreta, so chickens and ducks must be bought in regular supermarkets to avoid sick birds and dead birds; Pay attention to food hygiene, and be sure to cook chickens and ducks when eating them. When you buy pet birds in the flower, bird, fish and insect market, you must ensure that the birds are not sick; Wash your hands frequently when raising birds, keep your distance when watching birds, pay attention to air circulation and pay attention to hygiene and disinfection.
Medical workers and people who deal with avian influenza, as well as those who are physically and mentally ill, should be vaccinated against influenza. Experts believe that injecting human influenza vaccine not only reduces the occurrence of influenza, but also helps to block the combination and recombination of human influenza virus and avian influenza virus.
November 14th, 2005. The Ministry of Science and Technology announced in Beijing that researchers in China have successfully developed avian influenza vaccine for human use, completed all pre-clinical research work and will soon start clinical trials.
(Editor: Ye Huiling)