Epidemiology of 2009 pandemic influenza A(H1N1) virus infection in Henan province,2009-2010

Objective To analyze the epidemiological features of 2009 pandemic influenza A (H1N1) virus infection in Henan and provide the evidence for the prevention and control of the disease. Methods The surveillance data of 2009 pandemic influenza A (H1N1) virus infection in Henan were analyzed by descriptive epidemiological method. Results In the first half of August 2009, all the cases in Henan were imported ones from other countries or secondary ones of the imported cases, which mainly occurred in Zhengzhou. From mid-August 2009, the outbreaks began to occur in schools with rapid increase of the cases. The disease spread from urban area to rural area in the province, resulting in the shift of mostly affected population from students to farmers. Severe cases and deaths occurred. The epidemic became mild in mid-December 2009 and ceased at the end of February 2010. Conclusion Because of strict control measures in early phase of the epidemic, the spread of 2009 pandemic influenza A(H1N1) virus infection was slowed in Henan; The affected area and population were different in different stage, but no difference was observed on the incidence of severe cases. Students were the mostly affected population during outbreaks, from which the disease was transmitted to others. The epidemic pattern of 2009 pandemic Influenza A(H1N1) virus infection is different from that of seasonal influenza.