Symptomatic predictors of influenza virus positivity in children during the influenza season

Background. Symptomatic predictors of the etiology of infectious diseases are necessary when quick action is required in treatment, as with cases of influenza or anthrax, or for when patient isolation is required, as with cases of severe acute respiratory syndrome (SARS). Predictors of influenza virus infection during the influenza season have previously been evaluated in adult studies of the antiviral agent zanamivir; cough and temperature >= 37.8 degrees C predicted influenza virus positivity in 79% of those evaluated. Methods. Fever and other respiratory symptoms were examined to determine their value in predicting influenza virus-positive status in children. Data analyzed were from a clinical trial of zanamivir in children 5-12 years of age and from a trial of oseltamivir in children 1-12 years of age. Results. In the pediatric study of zanamivir, as in the adult zanamivir study, cough and fever were the best predictors of influenza virus infection; a temperature >= 38.2 degrees C plus cough predicted 83% (95% CI, 79%-88%) of illnesses that were determined to be influenza virus positive. Cough (positive predictive value, 70%; 95% CI, 64%-75%), but not fever, was the best predictor of influenza virus-positive status in children aged 5-12 years in the oseltamivir trials, but neither cough nor fever were successful predictors in young children 1-4 years of age. The latter findings appeared to be the result of less symptomatic diversity among patients recruited for this trial, such that subjects who were determined to be influenza virus positive and subjects who were influenza virus negative had similar symptoms. Conclusions. The results of these studies suggest that, during the influenza season, symptomatic predictors of influenza virus infection are applicable to identification of cases in children, although confirmation of predictive values in subjects 1-4 years of age may require further study of additional signs/symptoms.