Spatial and temporal cluster analysis of influenza epidemic in community surveillance of Tianjin city

Objective To analyze the spatial and temporal cluster of influenza epidemic in community based surveillance and to provide theological base for timely alert and field investigation.Methods Community-based influenza surveillance was carried out in primary hospital of Hangu street and four clinics,primary hospital of Datian county,and six village clinics from Oct 2009 to Feb 2011.Influenza B rapid test kit was used to test all influenza-like illness(ILI).The positive specimens were tested for influenza virus nucleic acid with real-time PCR.Space-time permutation scan statistic was used in the analyses and SaTScan software was used to identify clusters of ILI.Results A rural village outbreak in Oct 2009 was detected by community influenza surveillance.Influenza epidemic decreased in 2010.In the space-time permutation scan analyses,we found ten significant clusters in 2009.Four cluster districts were detected.The most likely clusters were located in Hangu street(rate ratio(RR)=27.44,P=0.0001).In 2010,only one most likely cluster was found in Xiaomashao village and Datian township(RR=12.53,P=0.0001).Two newH1N1 influenza outbreaks were confirmed.Conclusion Spatial and temporal analysis of influenza can timely ascertain the cluster of ILI and give the early alert,which can be used in public health practice.