Correlation between Baidu index of specific keywords and influenaz epidemics

Objective To analyze the correlation between Baidu index of specific keywords and influenza epidemics and to explore the utilization of the index in influenza surveillance.Methods Data on reported influenza like illness (ILI) cases and weekly positive rate of influenza virus isolation among the cases from October 2014 to March 2015 were collected form influenza surveillance sentinel hospitals in Tianjin city and 266 laboratory test confirmed influenza cases were surveyed with a questionnaire.Search queries related to influenza epidemics were gathered from Baidu database for the calculation of Baidu keyword index.Spearman correlation was used to analyze the relationship between influenza epidemics and Baidu keyword index.Results Among the confirmed influenza cases,65.04% performed internet searches about their early symptoms using search engine and "cold" was a keyword with the highest query frequency (67.72%) used by the cases.There was a highly close correlation between Baidu index for "fever" and the weekly positive rate of influenza virus isolation (r=0.808,P<0.05) and the correlation was more close when a one-week lag Baidu index for "fever" was adopted in the analysis (r=0.827,P<0.05).Conclusion Baidu index for "fever" could be considered as a earlier signal for incidence of influenza epidemic.