Hospitalization for respiratory syncytial virus bronchiolitis and disease severity in twins.

BACKGROUND Respiratory syncytial virus (RSV) is a common cause of lower respiratory tract disease and hospitalization in infants and young children. Infants of multiple births, who are often premature, might be more susceptible to developing a more severe RSV infection than singletons. OBJECTIVE To assess the impact of multiple births on the severity of RSV infection and define risk factors for acquiring RSV infection in infants of multiple birth. METHODS Clinical data on infants hospitalized with RSV infection between 2008 and 2010 were retrospectively collected. RESULTS Twins comprised 7.6% (66/875) of hospitalized infants with RSV bronchiolitis during the study period. Infants in the twin group were younger (122.4 +/- 131.7 vs. 204.5 +/- 278.8 days, P = 0.014), had a lower mean gestational age (35.3 +/- 2.6 vs. 38.6 +/- 2.5 weeks, P < 0.001), and were more likely to have been born prematurely compared with singleton infants (65.6% vs. 13%, P < 0.001). On a multivariable logistic regression analysis, young age, early gestational age and male gender were the only variables identified as risk factors for pediatric intensive care unit admission (P < 0.001, P < 0.001 and P = 0.03, respectively). In contrast, the mere fact of a child being a twin was not found to be a significant risk factor for disease severity. In addition, if one twin is hospitalized due to RSV infection, the other has a 34% chance of also being hospitalized with bronchiolitis. Young age was a significant risk factor for hospitalization of the second twin (P < 0.001) CONCLUSIONS: Our findings suggest that twins hospitalized with RSV bronchiolitis do not have an increased risk for severe infection as compared to singletons. However, a twin of an infant hospitalized with RSV infection has a considerable risk of also being hospitalized with bronchiolitis, thus close monitoring is recommended.