Visitors May Affect Utility of Wastewater Analysis for COVID-19 Surveillance, Study Finds

Wastewater-based epidemiology (WBE) may negatively be affected in areas with large numbers of visitors who can skew surveillance data, according to a study appearing this week in JAMA Network Open. Analyzing municipal sewage has proven to be a valuable tool for tracking the spread of SARS-CoV-2, but there are concerns that interpretation of wastewater surveillance data can be misleading in communities with mobile populations such as tourists and commuters. Because of that, modifications to existing WBE protocols may be necessary in such areas to overcome the confounding effects of mobile populations. In the new study, a team led by scientists from the University of Nevada, Las Vegas quantified and sequenced SARS-CoV-2 RNA obtained between early 2020 and early 2022 in sewage from a manhole near the visitor-dominated Las Vegas Strip, from the wastewater treatment plant (WWTP) serving the Strip and surrounding community, and from all other WWTPs in southern Nevada. They found that visitors may have disproportionately contributed to wastewater surveillance data without being reflected in local clinical surveillance effort, potentially leading to overestimates of infection burden and erroneously suggesting the circulation of a variant of concern in the local community. The findings, the study's authors write, support the importance of understanding the potential confounding effects of mobile populations in WBE applications and accounting for such effects