Epidemiology of documented viral respiratory infections and acute otitis media in a cohort of children followed from two to twenty-four months of age

Background. Viral upper respiratory infections (URIs) are considered major risk factors for acute otitis media (AOM) in young children. We studied the epidemiology and relative roles of different viruses in respiratory infect ions in a cohort of 329 Finnish children followed from 2 months to 2 years of age. Methods. A nasopharyngeal aspirate (NPA) was collected whenever the child h ad signs and/or symptoms of URI and tested for the presence of common respi ratory virus antigens or infectivity/nucleic acid (only rhinoviruses), Poss ible repeated detections of a given virus during a 30-day period were consi dered to represent a single designated virus-specific episode, AOM and URI episodes were defined in a similar way. Results. At least one virus was detected in 837 (41.7%) of the 2005 NPA spe cimens examined. Rates of URI and virus-specific episodes showed expected s easonal variation with major peak occurrences coinciding with or preceding those of AOM. The proportions of rhinoviruses, respiratory syncytial (RS) v irus, parainfluenza virus (PIV) type 3, influenza virus A and adenoviruses were 63.1, 14.7, 6.7, 6.7 and 6.2% of the total of 761 virus-specific episo des. Influenza virus B, PIV1 and PIV2 were each responsible for similar to1 % of the episodes. AOM was diagnosed in 870 URI cases (43.4%) and in 43.3% of cases associated with a virus-positive NPA. The latter figure was clearl y higher (57.7%) for RS virus-positive specimens. Conclusions. The seasonal coincidence of URI and AOM demonstrated the obvio us role of URI in the pathogenesis of AOM. The occurrence of rhinoviruses a nd RS virus in URI was strikingly more common than that of any other virus tested. Although rhinoviruses were definitely the most frequently found vir uses in NPA specimens, the association of RS virus with concurrent AOM was relatively higher than that of any other virus.