Frequency of acute respiratory illnesses and circulation of respiratory viruses in households with children over 3 surveillance seasons.

BACKGROUND The household has traditionally been the site for studying acute respiratory illnesses (ARIs). Most studies were conducted many years ago, and more broadly sensitive laboratory methods to determine ARI etiology are now available. METHODS We recruited and followed households with children over 3 annual surveillance periods and collected respiratory tract specimens from subjects with reported ARI. Virus etiology was determined by real-time reverse-transcription polymerase chain reaction (RT-PCR) analysis. RESULTS Individuals in larger households (defined as households with >4 members) and those in households with children aged <5 years had significantly higher ARI frequencies than others. ARI frequency generally declined with increasing age. Virus etiology was most likely to be determined in young children, who were also most likely to have virus coinfection. Overall, 16% of ARIs with 1 virus identified had ≥1 coinfecting virus. Rhinoviruses and coronaviruses were the most frequently identified agents of ARI in all age categories. Influenza virus and adenovirus were less frequently identified but were most likely to cause ARI that required medical attention. CONCLUSIONS Longitudinal studies in families remain a valuable way to study respiratory infections. RT-PCR has increased the sensitivity of virus detection, including coinfecting viruses, and expanded our ability to detect viruses now known to cause ARI.