(Hereinafter referred to as bird flu influenza A (H5N1) virus (Avian influenza virus)) from the avian influenza virus strains caused by certain subtypes of acute respiratory infection. In May 1997, China's Special Administrative Region 1 cases of three year-old child died of unknown causes multiple organ failure, the same year, eight menstrual U.S. Center for Disease Control and Prevention and the World Health Organization (WHO) National Influenza Center, Rotterdam, the Netherlands identified as avian A influenza virus, human influenza caused by H5N1, which is the world's first confirmed H5N1 avian influenza A viruses infect humans. Successively after the H9N2, H7N7 subtype H5N1 infection in humans and reports of re-infect humans.
Influenza referred to as influenza, is caused by influenza virus, commonly acute respiratory infectious diseases, spread of strong, Changcheng endemic, when the population of the new variant strain of influenza virus is still a lack of immunity, may lead to a global pandemic, which is characterized by sudden onset and rapid spread, 1918 ~ 1919 have occurred in a very wide range of world-wide pandemic, causing 20 million deaths.
I. Etiology
Avian influenza viruses are influenza A virus. Influenza A virus showed pleomorphic, in which spherical diameter of 80 ~ 120nm, with envelope. Sub-segments of the genome of single-stranded minus-strand RNA. In accordance with its outer membrane hemagglutinin (H Hemagglutinin) and neuraminidase (N Neuraminidase) of different protein antigen present can be divided into 15 H subtypes (H1 ~ H15) and 9 N subtypes (N1 ~ N9 ). In addition to influenza A virus infection of people, can be infected with pigs, horses, marine mammals and birds.
Blood clotting drug called H, for the rod-like protrusions with adhesive on the sensitive virus receptors and cause a variety of animals, agglutination of red blood cells took place;
Neuraminidase referred to N, for the dumbbell loaded processes, hydrolysis of cell surface glycoprotein with N-acetyl-neuraminic acid's role, so that replication of virus may be released from the cell surface.
Infection of human avian influenza virus subtype is mainly H5N1, H9N2, H7N7, one H5N1 infection in patients with severe illness, a high fatality rate.
Second, epidemiological
1, infection sources and routes of transmission
(A) the major source of infestation of infectious avian influenza or bird flu virus carrying chickens, ducks, geese and other poultry, especially chickens; but does not exclude other birds or pigs as a source of infection possible. The patient is the main source of infection, particularly in light patients and play an important role in latent infection, its difficult to be discovered, range of activities is also more extensive. Antigen has been confirmed from the animals (pigs, horses, birds) influenza virus with human influenza viruses are homologous, so animal influenza can be transmitted to people, but most of the popular early as the start of factors or long-distance play a role in transmission.
(B) the main mode of transmission through the respiratory tract spread through close contact with infected poultry and their secretions, excreta, water contaminated with the virus, as well as direct exposure to the virus strain infected. There is no definite evidence of spread from person to person.
2, immunity to human influenza viruses generally susceptible to infection with the virus to gain immunity, but retain a short time, only 8 to 12 months, no more than 2 years.
② partial immunity: infection are mostly localized mucosal surface of respiratory tract infection, the virus does not violate the blood, the incubation period is short, the role of serum antibodies to prevent infection is limited, and not lasting, it is more important for local immunity. Local mucosal secretion soon after the virus infection-specific SIgA, against virus attacks, acts as a major local protection.
① systemic resistance: the level of specific antibodies in the blood related to neutralizing antibody and hemagglutination inhibition antibody levels often parallel, 2 weeks after the illness reached its peak, after dropping 8 to 12 months after the disease fell to the level before. a, antibodies from the blood infiltrated the organization and its secretions, you can prevent the virus from entering and breeding starting role. b, newborns can be obtained from the mother's passive immunity, the first 2 ~ 3 months decreased significantly from 7 months to disappear. c, different age groups of children due to come into contact with influenza virus strains different from the blood antibody composition is also different. Cell-mediated immunity after infection has been confirmed that NK cell activity increased lethality and interferon
(C) the susceptible population is generally believed that all have the susceptibility of any age, but children under 12 years of age a higher prevalence serious condition. And unexplained dead poultry or infected, suspected of close contact with poultry infected with bird flu staff to high-risk groups.
3, age
Children and young persons contracting this disease, as many of 5 ~ 20 years of age the highest incidence. 4 to 5 months of age infants less vulnerable to infection, when a new subtype caused a pandemic, the incidence rate of all age groups close, but still 5 to 14-year-old children for multi-infection rate close to 50%.
4, season
Generally temperate and boreal Dongmochunchu flu epidemic in winter, when the disease prevalence of heavier.
WHO's influenza warning level
1: influenza virus spread among animals, but there was no human infection cases.
2: influenza virus spread among animals, these viruses have caused human infections, is seen as a potential influenza pandemic threat.
3: influenza virus in animals or between man and animal to animal transmission of such virus has caused sporadic or partial range of human infections, but there was interpersonal communication situation.
4: Influenza viruses spread from person to person and trigger a sustained outbreak. In this level, the spread of the risk of influenza compared with the previous one level "increased significantly."
5: the same types of flu viruses in the same area (eg North America) at least two countries, interpersonal communication, and cause sustained epidemic. While most countries at this level will not be affected despite a significant impact, but 5 warning means that large-scale flu outbreak is coming closer, to take measures to deal with the epidemic of time is running out.
6: the same types of flu viruses interpersonal communication occurs in two or more regions. At this level mean that the global nature of the epidemic is spreading.
留言列表
