Objective: To determine (1) the rates of single infection and coinfection with 7 respiratory viruses in pediatric inpatients undergoing respiratory viral cultures, (2) the rate of cytomegalovirus (CMV) coisolation in these patients and (3) the relationship between these and length of hospital stay.
Methods: A retrospective analysis of all respiratory viral cultures undertaken at the Royal Children's Hospital, Melbourne, Australia during a 4-year period.
Results: A total of 6706 respiratory virus cultures were identified, of which 3955 were the first nasopharyngeal or nasal specimen taken within 48 hours of admission from inpatients younger than 18 years of age. A virus was isolated in 1444 (36.5%) specimens. Coinfection was found in only 13 (0.9%) of these culture-positive specimens (0.3% of all 3955 specimens). After adjustment for age and seasonal variation in virus isolation, rates of coinfection were lower than would have been predicted for most respiratory viruses, particularly for respiratory syncytial virus (RSV) with influenza A, and RSV with any other virus. CMV was isolated in 174 (4.4%) specimens. Rates of CMV coisolation with respiratory viruses were lower than predicted from independent infection rates, with clearest evidence for the most common virus, RSV. The length of hospital stay varied between different viruses, but there was no evidence of increased length of stay in patients with coinfection (median, 1.9 days) compared with single infection (median, 2.5 days). The length of stay was longer in patients with CMV, especially when coisolated with a respiratory virus (a median of 3.9 days for coisolation compared with a median of 2.5 days for CMV isolation alone).
Conclusion: Coinfection with respiratory viruses is rare and in our study occurred less commonly than predicted from the independent virus isolation rates. Coisolation of CMV occurs less commonly than predicted with RSV. CMV coisolation, in contrast to respiratory virus coinfection, is associated with a longer length of stay.