Environmental surveillance reveals co-circulation of distinctive lineages of enteroviruses in southwest China's border cities, 2020–2022.

This article focuses on the diversity and genetic characterization of enteroviruses (EVs) circulating in border cities of southwest China through a two-year environmental sewage surveillance conducted from 2020 to 2022 in Yunnan Province. A total of 590 enterovirus isolates representing 21 serotypes were identified, with echovirus 6 (E6), echovirus 21 (E21), and coxsackievirus B5 (CVB5) being the predominant serotypes; all poliovirus (PV) strains detected were Sabin-like without wild-type or vaccine-derived polioviruses. Phylogenetic analyses revealed multiple distinct evolutionary lineages among the predominant serotypes, including a unique cluster of E21 not previously reported in China, suggesting ongoing cross-border transmission. The study highlights the sustained high diversity and activity of enteroviruses in these border regions despite COVID-19 pandemic interventions and underscores the value of environmental surveillance in areas lacking comprehensive clinical monitoring.