Increased Pediatric Respiratory Syncytial Virus Case Counts Following the Emergence of Severe Acute Respiratory Syndrome Coronavirus 2 Can Be Attributed to Changes in Testing.

A surge in RSV testing, rather than in viral circulation, likely underlies the increased case counts observed in 2021-2023. These findings warrant a critical assessment of the immunity debt hypothesis and highlight the importance of considering the testing denominator when surveillance strategies are dynamic.