Study on case definition of influenza like illness in children for influenza surveillance

Objective To probe into the case definition of influenza like illness(ILI)in children for influenza surveillance.Methods Retrospective analysis was conducted on the influenza surveillance data of Wuhan area from 1994 to 2004.Results Of 1 003 subjects selected in this study,301(30.01%)were confirmed to have influenza.The incidence of influenza was significantly different between two age groups(P=0.024).Nasal symptoms(P=0.0242)and sore throat(P=0.0091)were significantly different between the infections of influenza A and influenza B viruses.Temperature(OR=1.555),duration of symptoms(OR=2.369),cough(OR=2.369),nasal symptoms(OR=1.873),and sore throat(OR=2.061)were significantly associated with influenza infection in logistic regression analysis.The combination of cough and nasal symptoms/sore throat had the positive predictive value of 41.3%,negative predictive value of 78.4%,sensitivity of 58.8% and specificity of 64.1% for predicting the influenza infection among children.Conclusions A better case definition of influenza like illness in children for influenza surveillance is:fever(temperature ≥38 ℃),cough accompanied by nasal symptoms or sore throat.