Seasonal respiratory infections, like RSV (respiratory syncytial virus) are peaking in unexpected months after a year-long low, likely brought on by COVID mitigation policies like lockdowns, masking, and social distancing. Instead of peaking in the winter, RSV peaked in the summer of 2021 and 2022. It is not yet clear if this shift in seasonality will persist. Health systems have been challenged with these unpredictable conditions and could benefit from an early warning before the next wave of RSV cases. We describe trends seen in RSV waves by region.

We analyzed claims with RSV diagnosis codes, by region, January 2018 – December 2022, from open-source, pre-adjudicated professional (Dx) and institutional (Hx) medical claims. These data have a lag-time of 2-4 weeks between when a visit occurs and when the claim appears in the data. Data are available within 90 days of events in the real world. Dx claims comprise more than 180 million patients per year from about 94% of AMA licensed physicians. Hx claims comprise 60 million patients per year from more than one million providers.

We detected 3,026,257 patients with 3,670,606 RSV claims between January 2018 – December 2022. There were ~577K, 649K, 339K, 719K, and 743K patients with RSV diagnoses each year 2018-2022, respectively. RSV claims increased the most from 2020 to 2021 (+112%); however, 2022 had the most RSV claims in the study period. The earliest RSV claims in each wave were seen in the South region, with subsequent increases observed in the Midwest, Northeast, and West, in that chronological order. The data examined suggest that when RSV is increasing at a rate of roughly 1.5K patients per week in the South, a new wave of cases is beginning. Further, we can expect that wave to peak within 4-6 months of signal detection.

A threshold based on existing weekly rates of change in the South could serve as a warning of anticipated RSV waves in other regions. An early warning system for RSV waves would empower health systems to prepare for and manage strains on resources with more predictability. Timely data with a robust, stable sample size, such as that provided by IQVIA Dx and Hx claims, are vital in the surveillance of emerging burdens to health systems such as RSV.