Systematic surveillance of influenza, syncytial respiratory, parainfluenzaand adenovirus in children with acute respiratory infections

Background: The efficacy of influenza vaccination programs depends on the a ntigenic similitude between vaccine and the influenza virus circulating in the community. therefore the surveillance of clinical activity and antigeni c features of influenza virus Is of utmost importance. Aim: To perform a sy stematic surveillance of clinical activity and antigenic characteristics of influenza virus. Material and methods: Since 1996 and during the cold mont hs (May to September), 20 samples of tipper respiratory secretions per week , were obtained from children with acute respiratory infections; consulting to the emergency room of a public hospital. Using indirect immunofluoresce nce and cellular cultures, the presence of influenza, syncytial respiratory , parainfluenza and adenovirus was assessed. The weekly number of consultat ions in the emergency room and the number of hospital discharges due to acu te respiratory infections, were registered. Results: Influenza and syncytia l respiratory were the predominant virus detected since 1996. In 1996 and 1 998, the weekly detection of influenza virus followed a single seasonal cur ve. The maximal weekly positively results reached 85 and 80% of the obtaine d samples, respectively. During 1997, two curves of influenza virus activit y were observed, but none reached more than 50% of weekly positive samples. The demand for outpatient care evolved in parallel to the weekly detection of influenza virus. The hospital discharges due to acute respiratory infec tions paralleled the syncytial respiratory virus detection rates. Conclusio ns: This surveillance model is effective for the detection of influenza and other virus responsible for acute respiratory, infections and their relati onship with the demand for health care during the cold months.