Early Detection of Pertussis Related Activity by Wastewater Surveillance of Bordetella pertussis- and Bordetella parapertussis- Associated DNA Concentrations in Osaka, Japan.

Pertussis causes recurrent outbreaks worldwide. Clinical surveillance can be affected by healthcare-seeking behaviour, diagnostic practices, testing sensitivity, and reporting delays. This study evaluated the utility of wastewater surveillance (WWS) by quantifying Bordetella-associated IS481 and IS1001 DNA concentrations. Weekly wastewater samples were collected from four treatment plants in Osaka Prefecture, Japan, between April 2023 and July 2025, and IS481- and IS1001-associated DNA concentrations were measured using quantitative PCR. The putative B. pertussis-associated IS481 DNA concentration increased markedly from 2024 onwards. Both threshold-based onset detection and cross-correlation analysis indicated that the wastewater IS481 DNA concentration preceded reported cases by one to several months. In contrast, the B. parapertussis-associated IS1001 DNA concentration exhibited a transient peak in 2023, which aligned with contemporaneous clinical reports but remained at low levels thereafter. These findings suggest that WWS may detect increases in pertussis-related activity earlier than clinical reporting and highlight the potential of WWS as a complementary tool to clinical surveillance for monitoring respiratory infectious diseases.