Wastewater surveillance of SARS-CoV-2 from aircraft to citywide monitoring

Wastewater monitoring is highly efficient in SARS-CoV-2 surveillance for tracking virus spread through travel, surpassing traditional airport passenger testing. This study explored the links between SARS-CoV-2 contents and variants from aircraft to city, assessing the impact of detected variants from international travellers versus the local population. A total of 969 variants using next-generation sequencing (NGS) were examined to understand the links between-aircraft, Arlanda airport, wastewater treatment plants (WWTPs), and Stockholm city-and compared these to variants detected in Stockholm hospitals from January to May 2023. SARS-CoV-2 contents in WWTPs reflected local infection rates, requiring analysis from multiple plants for an accurate city-wide infection assessment. Variants initially detected in aircraft arriving from China did not spread widely during the study period. RT-qPCR is adequate for the detection of specific variants in wastewater, including Variants Under Monitoring. However, NGS remains a powerful method for identifying novel variants. Wastewater monitoring was more effective than clinical testing in the early detection of specific variants, with notable delays observed in clinical surveillance. Furthermore, a broad range of variants are detected in wastewater that surpasses clinical tests. This underscores the vital role of wastewater-based epidemiology in managing future outbreaks and enhancing global health security.