Epidemiological Analysis of Seasonal Influenza Epidemic in Taiwan in 2006/2007

Chiu-Wen Chang

2008 Vol.24 NO.12

Correspondence Author： Chiu-Wen Chang

Abstract：

To investigate severity of influenza epidemic in Taiwan in 2006/2007, we used disease surveillance results of the CDC, including reported cases of influenza from the Sentinel Physician Surveillance System, the School-based Infectious Disease Surveillance Reporting System, and Laboratory Surveillance System, and the cases of influenza with severe complications from the National Notifiable Disease Surveillance System from June 1, 2006 to June 30, 2007. The results showed that there were more cases of seasonal influenza in 2006/2007 than in 2005/2006. The peak happened in late 2006 and 2007, but cases started to increase in the 42nd week of 2006 in the School-based Infectious Disease Surveillance Reporting System, one month earlier than two other surveillance systems (cases in the Sentinel Physician Surveillance System increased since the 47th week of 2006, and numbers of viral isolation increased since the 48th week of 2006). The results of influenza virus isolation showed that 77.0% were influenza virus type B, and the major type was B/Malaysia/2506/2004. In this influenza season, 154 cases of influenza with severe complications were reported from the legal infectious disease system, and 34 were confirmed cases. The major viral type was also type B influenza virus. When Poisson distribution was used to estimate 95% confidence interval (95% CI) of the incidence of influenza with severe complications, it was 0.15 cases per one hundred thousand people per year (95%CI: 0.10-0.21). The incidence in northern Taiwan was 0.24 cases per one hundred thousand people per year (95% CI: 0.15-0.35), higher than other areas in Taiwan. The incidence among people between 0 and 9 years old was 0.51 cases per one hundred thousand people per year (95% CI: 0.27-0.88), higher than people of other ages. In summary, there are more cases of seasonal influenza in Taiwan in 2006/2007 than in 2005/2006, and the peak was between late 2006 and early 2007. The major viral type was type B, B/Malaysia/2506/2004.
Keywords:influenza, disease surveillance, influenza virus