Influenza viruses belong to orthomyxoviriaceae in virology. Its genetic material consists of 8 independent single-stranded negative strand RNA fragments of different sizes, encoding 10 proteins in total. Its characteristic is prone to mutation. It is divided into three types: A, B and C, among which the A influenza virus often produces antigenic variation, which can infect people and a variety of animals, and often causes a pandemic and a small epidemic. Influenza B virus mutates less and can infect humans, causing outbreaks or mini-pandemics. Type C is relatively stable, can infect humans, mostly sporadic cases. At present, influenza virus has been breaking out in the world from time to time, so it is particularly important to establish a scientific and rapid diagnostic method.
At present, the commonly used detection methods of influenza virus detection methods mainly include virus isolation and identification, serological methods and molecular biological methods.
Isolation and identification of viruses Virus isolation is one of the traditional methods for influenza virus detection, including chicken embryo inoculation and cell culture. At present, motor dog kidney cells (MDCK) were used as host system for influenza virus isolation. It takes four to five days to test for the flu virus.
Immunological testing methods
Serological diagnosis is mainly to detect the level of antibodies in the patient's serum, that is, using known influenza virus antigens to detect antibodies in the serum. The serum antibody assay cannot detect antibodies before they are produced in the initial stage of infection or at levels below the detected concentration.
There are two main methods for detection of viral antigens: direct fluorescent antibody detection and immunocolloidal gold chromatography. The direct fluorescent antibody detection method is to use fluorescent pigment to label the antibody molecules, and then combine with the specific antigen in the sample, and observe the virus antigen and its existing position in the cell by fluorescence microscope. Immune colloidal gold chromatography technology is easy to operate without any special instrument. The test results are intuitive and convenient for basic units and field use.
Viral nucleic acid detection
The commonly used methods for viral nucleic acid detection include nucleic acid hybridization, reverse transcription-polymerase chain reaction, multiple reverse transcription-polymerase chain reaction, enzyme linked immunoPCR, and real-time quantification. PCR, dependent nucleic acid sequence amplification, fluorescence PCR and other methods. In recent years, the detection and typing of influenza virus using gene chip has become a hot spot in the research. It can detect many kinds of viruses at the same time, especially suitable for the characteristics of multi-subtype and easy mutation of influenza. However, this method requires high experimental conditions. The general advantages of nucleic acid detection are fast detection speed, strong specificity and easy operation.