Epidemiology of RSV-A and RSV-B in Adults and Children with Medically-Attended Acute Respiratory Illness over Three Seasons

BackgroundRSV is a frequent cause of respiratory illness less often diagnosed outside hospital settings; thus, overall prevalence of RSV-associated illness is under-recognized. Information about presence of RSV among those with chronic conditions is especially needed with recent advances in vaccine development. MethodsParticipants prospectively enrolled in an ambulatory surveillance study of respiratory illness (MFIVE) were tested by RT-PCR for RSV and influenza. Participant and illness characteristics were collected by in-person survey and EMR review. Chronic conditions were characterized by the Multimorbidity-weighted index (MWI). Viral factors, including subtype and viral load, were compared between RSV-A and RSV-B. Multivariate logistic regression models were used to compare participant and illness characteristics between those with RSV and those with influenza. Comparisons were also made across RSV subtypes. ResultsAmong 4,442 individuals enrolled in MFIVE from fall 2017 to spring 2020, 9.9% (n=441) had RSV detected. RSV+ participants with increased viral load had increased odds of illness lasting [≥] 7 days [ORadj=2.39 (95% CI: 1.03-5.51) p-value=0.04]. Adults with RSV had higher median MWI scores compared to influenza and RSV/influenza-negative (1.62, 0.40, 0.64, respectively). ConclusionsOur findings support the need for ongoing RSV surveillance, particularly in older adults and those with multimorbidity. Our findings support a recognition of multimorbidity as a significant contributor to RSV-associated MAARI among outpatient adults, with particularly notable impacts among adults under 65.