Environmental Surveillance Can Dynamically Track Ecological Changes in Enteroviruses

Environmental surveillance can be used to trace enteroviruses shed from human stool using a sewer network that is independent of symptomatic or asymptomatic infection. In this study, the local transmission of enteroviruses was analyzed using two wastewater treatment plants, which were relatively close to each other (15 km), designated as sentinels. Influent was collected at both sentinels once a month from 2013 to 2016, and viruses were isolated. Using neutralizing tests with type-specific polyclonal antisera and molecular typing, 933 isolates were identified as enteroviruses. Our results showed that the frequency of virus isolation varied for each serotype at the two sentinels in a time-dependent manner. Because echovirus 11 (Echo11) and coxsackievirus B5 isolates showed a high frequency and were difficult to distinguish, they were further grouped into various lineages based on the VP1 amino acid sequences. The prevalence of each lineage was visualized using multidimensional scaling. The results showed that Echo11 isolates of the same lineage were isolated continuously, similar to coxsackievirus B5 isolates of three lineages. Conversely, Echo1, Echo13, Echo18, Echo19, Echo20, Echo29, and Echo33 were isolated only once each. Our findings suggested that if an enterovirus is imported into the population, it may result in small-scale transmission, whereas if there are initially many infected individuals, it may be possible for the virus to spread to a wide area, beyond the local community, over time. In addition, our findings could provide in-sights into risk assessment of transmission for importation of poliovirus in polio-free countries and regions. IMPORTANCE In this study, we showed that environmental enterovirus surveillance can be used to monitor the propagation of nonpolio enteroviruses in addition to poliovirus detection. Since epidemiological studies of virus transmission based on the past were performed using specimens from humans, there were limitations to research design, such as specimen collection for implementation on a large-scale target population. However, environmental monitoring can dynamically track the ecological changes in enteroviruses in the region by monitoring viruses in chronological order and targeting the population within the area by monitoring viruses over time. We observed differences in the transmission of echovirus 11 and coxsackievirus B5 in the region according to lineage in a time-dependent manner and with a multidimensional scaling pattern.