Wastewater Surveillance Uncovered the Impacts of the\nTiming of COVID-19 on the Epidemic Trajectories of Other Respiratory\nDiseases in Two Northeastern Cities in China

In\nthis study, we conducted quantitative polymerase chain reaction\n(qPCR)-based wastewater surveillance for 12 prominent respiratory\npathogens in two northeastern cities of China, Dalian, and Benxi,\nto understand the cocirculation patterns between COVID-19 and other\nrespiratory diseases from October 2022 to July 2023. Wastewater surveillance\nrevealed that Influenza A virus (IAV) and respiratory syncytial virus\n(RSV) sewage concentrations exhibited an upward trend from October\n2022 in both cities but with distinct epidemic trajectories. In Dalian,\nIAV and RSV sewage concentrations both peaked in early December, followed\nby a rapid decline since the emergence of COVID-19 on November 23,\n2022. In Benxi, two bell-shaped curves were observed for IAV and RSV\nsewage concentrations, both peaking in mid-December of 2022, even\nthough severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)\nemerged in wastewater on December 8, 2022. After a rapid decline in\nSARS-CoV-2 sewage concentrations in January 2023, a new wave of IAV\nin wastewater occurred between February and early April in both cities,\nfollowed by a surge of SARS-CoV-2 RNA in early May. Meanwhile, an\nout-of-season epidemic of RSV from March to May was observed in Benxi\nbased on the cities’ sewage concentrations. This study highlights\nthe impact of the timing of COVID-19 on the epidemic trajectories\nof other respiratory diseases.