Influenza surveillance in Hainan province,2007 to 2008

ObjectiveTo get an insight into the variability and prevalence characteristics of influenza in Hainan from 2007 to 2008.MethodsDescriptive analysis and χ²-test were applied to analyze the flu-like cases and virologic surveillance results during 2007-2008 based on the data from influenza sentinel hospitals in Hainan province.ResultsInfluenza-like illness(ILI)occurred with high incidence during summer and winter.The proportion of ILI in different areas were significantly different during 2007-2008(χ² = 1033,P<0.01).The cases were mainly distributed in 0-4 and 5-14 year age groups,accounting for 70.17%of all ILI cases,and there were significant differences in ILI incidence among different age groups(χ²=1400,P<0.001).The positive rate of influenza virus isolation was 11.26% in 2007 and 6.62% in 2008.Influenza B viruses were predominant(55.26%)in 2007,but the dominant virus strains in 2008 were influenza A(H1N1)(41.18%)and influenza B viruses(37.25%).The positive rate of isolation in 2007 was higher than that in 2008(χ²=9.69,P<0.01).ConclusionSummer and winter are the key periods for influenza prevention and control in Hainan province,and it is necessary to strengthen the prevention and control of influenza among adolescents and children.Meanwhile,the dominant virus strain change needs to be monitored.