H1N1 diagnostic criteria for the test
Posted on October 31, 2009
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In March of this year in Mexico and the United States has occurred in a new pathogenic influenza H1N1 influenza virus, is now occurring in many countries in the world and spread, causing the World Health Organization and governments of the widespread concern, and actively take strict measures to prevent its spread . The influenza virus is a new variant of an old virus. Influenza virus belongs to Orthomyxoviruses Branch, is a negative chain of single-stranded RNA virus. It is divided into Influenza A (A), B (B) and C (C). There are many processes virus surface glycoprotein molecules, mainly haemagglutinin (H) and neuraminidase (N), also according to their antigenic differences be divided into 16 H subtypes (H1-H16) and 9 a N subtypes (N1-N9). Thus, H1N1 is a haemagglutinin and neuraminidase type 1 in combination. The antigens of these subtypes are continuing to variation, from quantitative to qualitative change on the emergence of a new type. This is a new type of Influenza A H1N1. Because the Influenza A H1N1 in 1918 has attracted world-wide pandemic (Spanish flu). In 1957 there H2N2 pandemic (Asian flu), 1968, there were a pandemic H3N2 (Hong Kong flu), H1N1 variants in 1977, is also popular (Russian influenza). This might be it H1N1 influenza in humans, animals or the environment, a new mutation occurs.
For the timely and effective prevention and control of influenza A H1N1 influenza, China’s Ministry of Health issued timely treatment program. At present the majority of our case is due to imported cases, with emphasis on prevention and control of the spread by air channels. In patients with suspected or confirmed in close contact with the crowd for medical observation cases, there is another history of exposure to symptoms of suspected cases, diagnosed by testing positive for Influenza A H1N1 confirmed cases. Can see that the key lies in whether the evidence of diagnostic testing, testing evidence in a clear diagnosis is crucial. So, what evidence of diagnostic tests do?
1, Influenza A H1N1 influenza virus nucleic acid amplification. Since the patient’s respiratory tract specimens (eg nasopharyngeal secretions, mouth rinse fluid, tracheal aspirate or respiratory secretions and other materials) with RT-PCR (reverse transcription – polymerase chain reaction) to amplify this virus-specific nucleic acid fragments, according to the size of nucleic acid fragments can be identified, you can sample to be taken 2 hours after the outcome. China’s Ministry of Health has provided standardized test method, by the Centers for Disease Control at all levels to implement and issue reports, can be quickly and reliably make a diagnosis.
2, cell culture method of separation of Influenza A H1N1 influenza viruses. This method requires a longer time, but it is the most reliable diagnostic method. Classification of viruses can be used to analyze the genetic changes in understanding of fashion trends, right to determine its prevalence in the world will be of great value in the law. More importantly, with the strain of the virus in order to produce the vaccine. Recently, the World Health Organization in China from the standard strains obtained by the number of vaccine production in China to expedite the production of vaccine. From the focus groups (cases for the region around the crowd, the elderly, children, etc.) began a general prevention and control of influenza H1N1 vaccine is the most reliable method. With the cell culture method of separation of Influenza A H1N1 influenza virus, the time required for a long, technical requirements are high, but this is the most reliable diagnostic method.
Third, rapid antigen influenza A H1N1 influenza inspection. Rapid detection tools available from the patient’s respiratory tract specimens (as above), using immunological techniques to the known antibody, to examine samples of the virus nucleoprotein antigen (NP antigen) or matrix protein (M1) or the influenza virus H Asia antigen. This is the timely detection of suspected cases, or do not have the nucleic acid amplification conditions may play a role, but will need further impose nucleic acid amplification positive or positive serology can be judged as confirmed cases.
4, serological examination. In patients with early stage disease to take blood tests Influenza H1N1 influenza virus antibodies, when more negative or low antibody titers. After two weeks after a antibodies significantly increased. Therefore, the patient’s recovery and then measured blood and, if antibodies 4-fold higher, indicating that there have been a patient of this influenza virus infection, but also for confirmed cases. This epidemiological investigation and understanding of the population of antibody levels and to determine the effect of the vaccine are important means.
5, auxiliary diagnostic index. The blood leukocyte count did not increase or decrease. Often in patients with severe reduction in white blood cells and lymphocytes, often reducing the platelet.
Influenza A H1N1 flu threat to humanity so great, mainly because this new human influenza virus have no immunity. Born before 1957 may have infection or contact with H1N1 virus, but antibodies have also been very low and the current H1N1 influenza viruses target is not strong. Thus, an important means of prevention is vaccination, China is going to mass production. However, with the variation of influenza virus antigen, a vaccine targeted also need to change. It can be said of influenza vaccination can not have once and for all vaccines.
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