Epidemiologic characteristics of influenza in Guangdong Province,2005-2007

Objective To understand the epidemiologic characters of influenza in Guangdong Province from 2005 to 2007 to take proper action for prevention and control of influenza.Methods Descriptive epidemiological analysis was made on surveillance data of influenza surveillance system of Guangdong Province from 2005 to 2007.The surveillance data contained information on patients with influenza-like illness(ILI) visiting out-patient departments of influenza sentinel hospitals,ILI outbreak surveillance information all over the province,and pathogenic surveillance data of ILI specimens collected from sentinel hospitals surveillance system and ILI outbreaks.Results The surveillance data from 2005 to 2007 showed that the peak of epidemic of influenza in Guangdong Province was from March to July,while the influenza activities of each year were unique.The peak of influenza activity was from March to May in 2005,which was caused by influenza A(H3N2) and A(H1N1) viruses.The influenza activity appeared double peaks in 2006,i.e.,one was from March to April caused by influenza B(Victoria) viruses,and the other in June caused by influenza A(H1N1) viruses.There was only one peak in June in 2007 which was caused by influenza A(H3N2) viruses.Provincially,121 ILI outbreaks were reported in 2005,172 in 2006 and 40 in 2007,respectively.The type of influenza virus which caused outbreaks was the same as the surveillance results of sentinel hospitals in the past three years.Over 92 percent of ILI outbreaks reported occurred in schools and kindergartens,The surveillance data from sentinel schools showed that the peak of weekly ILI outpatient consultant rate in sentinel schools appeared one week earlier than that from other sentinel hospitals.Conclusion The seasonal peak of influenza epidemic in Guangdong Province was in spring and summer,as a single peak or double.Most influenza outbreaks occurred in primary and secondary schools and nurseries,which should be the focus of prevention and control.