Analysis of Respiratory Syncytial Virus Episodes During and Outside Typical Season in US, 2016–2020

Overview

This study analyzed hospital-based RSV episodes in the US from 2017 to 2020, comparing narrowly defined in-season (December–February) and off-season (June–August) cases. It identified demographic disparities, higher antibiotic use, and greater prevalence of underlying conditions among off-season pediatric cases.

Background

Respiratory syncytial virus (RSV) is a common respiratory pathogen causing mild to severe illness, especially in infants, older adults, and those with chronic conditions. RSV typically follows a seasonal pattern in temperate climates, peaking in fall, winter, and spring. However, variability exists in season timing and intensity, with off-season cases occurring. Understanding RSV epidemiology, including off-season episodes, is crucial for optimizing emerging preventive interventions such as vaccines and monoclonal antibodies.

Data Highlights

Key Findings

• Among pediatric RSV episodes, approximately 60% of both in-season and off-season cases occurred in infants.
• Black and Hispanic pediatric patients were disproportionately represented in off-season episodes compared to in-season (Black: 22% vs 15%; Hispanic: 30% vs 19%; P < .0001).
• Similar racial and ethnic disparities were observed among adult RSV cases.
• Off-season pediatric episodes had a higher proportion of antibiotic use (54%) compared to in-season episodes (45%; P < .0001).
• Infants and children aged 1–4 years with congenital or chronic conditions were more likely to experience off-season RSV episodes (P < .0001).
• RSV seasonality showed geographic and temporal variability, with typical season onset between mid-September and mid-November and offset between mid-April and mid-May.

Clinical Implications

Clinicians should be aware that RSV can cause significant illness outside the traditional season, particularly among infants, racial and ethnic minority groups, and children with underlying conditions. Off-season cases may be associated with higher antibiotic use, highlighting the need for judicious antimicrobial stewardship. These findings support the importance of year-round vigilance and tailored preventive strategies as RSV immunization options become available.

Conclusion

RSV episodes occur both during and outside the typical season with notable demographic disparities and increased antibiotic use in off-season pediatric cases. Understanding these patterns is essential for optimizing prevention and management strategies across all age groups.

References

1. CDC/NREVSS -- National Respiratory and Enteric Virus Surveillance System
2. Premier Healthcare Database -- Data Source Description
3. Study Authors, 2016–2020 -- Analysis of Respiratory Syncytial Virus Episodes During and Outside the Typical Season—United States