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Influenza A or B? 流感甲還是乙?

(added on 2018/03/15)

©2018 SpatioEpi.com
Map created by CUHK SpatioEpi Group


Between the end of 2017 and the beginning of 2018, the influenza epidemic has occurred not only in Hong Kong but also the world. The map shows the distribution of main influenza subtype during this Winter influenza season of the northern hemisphere (between week 45 of 2017 and week 8 of 2018). These main reporting subtypes were confirmed in laboratory, and could be categorized as subtype A, B and C. Subtype A can be further classified as A (H1N1) and A(H3N2), etc., and subtype B as B (Yamagata lineage) and B (Victoria lineage), etc. Subtype C is however not common. It can be seen that the circulating subtype of a place is the same as that among countries nearby. For instance, the main subtype in China and her nearby south-east Asian countries is B, and the main subtype in North America (USA and Canada) is A(H3N2). From another perspective, there’s little relationship between the virus circulating in USA and Hong Kong or China.
The reported influenza subtype data on the maps were obtained from the WHO FluNet http://www.who.int/influenza/gisrs_laboratory/flunet/en/.

2017年底至2018年初的流行性感冒(簡稱流感)不止肆虐香港,更加?行國際。地圖中顯示北半球冬流感季期間(2017年第45週開始,截至2018年第8週)各國家的主要流感類型分佈。這些類型經實驗室確定,主要分為甲型、乙型及丙型。甲型流感可細分為甲型H1N1及甲型H3N2….等。乙型則可再細分為乙型流感病毒株的山形系及維多利亞系等。丙型則屬少數。地圖可見鄰近國家的主要流感類型是同一種,如中國及鄰近東南亞國家的流感類型是乙型,而北美洲(美國及加拿大)則是甲型H3N2 。從另一角度看,在美國擴散的流感病毒和中國或香港所傳播的並不一樣。

Related Article

Human influenza 人類流感

Influenza is a respiratory infection caused by the influenza virus, different forms of which are normally circulating in not just human beings but pigs and birds. All influenza viruses are divided into A, B and C, and further distinguished by their H and N antigens. There are currently 18 H (standing for haemagglutinin) and 11 N (standing for neuraminidase) antigens. Epidemics occurred when novel viruses are introduced to the human population. Pandemic influenza A (H1N1), previously referred as Swine flu, was an example causing worldwide outbreaks in 2009. The genetic structure of this influenza virus contains segments from pig, bird and human, reflecting the occurrence of reassortment. Studies suggested a case fatality rate of 0.4% for the novel infection, and a higher tendency for causing disease in young people compared to other forms of seasonal flu. Since 2009, the same virus has continued to cause outbreaks in different populations at different timepoints.


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