Data source: Stanley Ho Centre for Emerging Infectious Diseases, The Chinese University of Hong Kong
Map created by CUHK SpatioEpi Group
To many people, influenza may just be a minor ailment. Caused by the influenza virus, infected individuals may require hospitalization if the condition is severe. Elderly people are particularly susceptible to severe influenza because of weakened immunity. The map shows the distribution of influenza cases admitted to a district hospital between March and November 2010 in Hong Kong. The dots and circles represent the resident location of influenza patients requiring hospitalization. People at or above the age of 65 people accounted for a majority of the influenza patients, many of which were residents of elderly homes (house symbols). It is not uncommon to find multiple patients (circles) in the same elderly home, which may be a result of cross infection. Yearly vaccination is an important means of protecting old people from severe influenza diseases. Data used in this map were obtained from a study conducted at the Alice Ho Miu Ling Nethersole Hospital in Tai Po District in the North East of Hong Kong.
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.