In late 2022, there was a significant increase in the prevalence of RSV in the northeastern United States. This surge occurred concurrently with the beginning of the traditional influenza season and the ongoing circulation of SARS-CoV-2. We retrospectively analyzed respiratory testing data at a regional reference laboratory from September 2022 to April 2024 to characterize the prevalence and incidence of co-detection of RSV, influenza A, influenza B, and SARS-CoV-2 in the northeastern United States. The positivity rates were found to be 16.68% for SARS-CoV-2, 11.66% for influenza A, 0.83% for influenza B, and 9.11% for RSV during the study period. Co-detections were observed in 0.49% of samples, with SARS-CoV-2/influenza A co-detection being the most common. Co-detections occurred less frequently than expected based on individual positivity rates. During the study period, influenza B positivity increased over 10-fold, SARS-CoV-2 positivity decreased by 60%, and co-detection was more prevalent in the pediatric population.