Contribution of influenza and respiratory syncytial virus to community cases of influenza-like illness: an observational study

Background Respiratory syncytial virus (RSV) is an important cause of lower-respiratory-tract infection in children and elderly people, but its effect in other age-groups is uncertain. We did a community-based observational study of RSV infection in community-dwelling individuals of all ages who presented to general practices in the UK with influenza-like illnesses during three successive winters (1995-96,1996-97, and 1997-98). Methods Nasopharyngeal swabs routinely submitted for virological surveillance were examined by multiplex reverse transcription PCR for influenza A and B viruses and, RSV A and B, and findings were related to the clinical incidence of influenza-like illness and acute bronchitis at that time. RSV strains identified were compared with those obtained from hospital admissions. Findings 480 RSV and 709 influenza viruses were identified from a total of 2226 swabs submitted. Both types of virus were found in all age-groups for between 12 and 20 weeks In each winter. RSV A accounted for 60% of RSV detections. Similar strains of RSV were present in hospital and community patients within the same year, but there were different lineages each year. Interpretation In individuals diagnosed with Influenza-like illness, there is a substantial potential for confusion between illnesses caused by influenza and those caused by RSV. The burden of illness attributable to each needs to be clarified to define optimum management routines.