Seasonal Incidence of Medically Attended RSV and Influenza Illness in Children 6-59 Months Old
Background: Respiratory syncytial virus (RSV) and influenza are major causes of seasonal respiratory illness in children. The incidence of medically attended, laboratory confirmed illness with these pathogens is not well documented. We estimated the seasonal incidence of medically attended RSV and influenza in a Wisconsin community cohort of children 6 to 59 months of age during 4 seasons (2006-07 through 2009-10).
Methods: Children with medically attended acute respiratory illness (MAARI) were prospectively enrolled during annual studies of influenza vaccine effectiveness; enrollment occurred for 10-12 weeks and included the period of peak influenza and RSV activity. Respiratory swabs were tested for RSV and influenza by multiplex RT-PCR. Results from enrolled children were used to estimate RSV and influenza cases among non-enrolled children with MAARI in three age groups: 6-11, 12-23 and 24-59 months. Results for the enrollment period were weighted to estimate seasonal incidence (week 40 to 18) based on the statewide proportion of RSV and influenza cases that occurred outside the enrollment period.
Results: There were 2800 to 3073 children in the community cohort each season; 627 (27%) of the total 2326 enrolled children with MAARI had RSV and 235 (10%) had influenza. Overall seasonal incidence (cases per 10,000) among children 6-59 months old was 1725 (95% CI, 1609-1850) for RSV and 702 (95% CI, 549-896) for influenza. RSV incidence was higher than influenza in every age group and season; it was highest among children 6-11 months old (2863) and 12-23 months old (2473) (figure 1). Influenza incidence did not differ significantly by age group.
Conclusion: . RSV incidence was higher than influenza in every season and age group. Children 6-23 months old had a higher incidence of both RSV and influenza compared to those aged 24-59 months. The burden of RSV is high in young children and points to the ongoing need to develop safe and effective preventive interventions.
MedImmune: Project scientist - MedImmune funded grant, Research grant
M. Sundaram, MedImmune, LLC: Project scientist on MedImmune-funded grant, Research grant
D. Mcclure, None
J. Meece, None
F. Sifakis, AZ/Medimmune: Employee and Shareholder, Salary and Share grants
R. Gasser Jr., AZ/Medimmune: Employee and Shareholder, Salary and Share grants
H. Mclean, MedImmune: Collaborator, Research grant
E. Belongia, Medimmune LLC: Grant Investigator, Grant recipient