Data source: Various newspapers
Map created by CUHK SpatioEpi Group
The map shows the flight paths of the first 6 cases of laboratory-confirmed “swine flu” in the region covering Mainland China and Hong Kong, before entering our home cities. As a respiratory infection, influenza virus is transmitted through person-to-person contacts, and “swine flu” is no exception. In modern days, the high intensity and extensiveness of air travel has shortened the distance between people, bringing the source of infection closer to distant populations in almost no time. Presumably originating in Mexico, the virus found its way through long distance air travel to Asian communities. The map has incorporated information obtained from multiple sources in the media.
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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