Shedding of SARS-CoV-2 genome in wastewater after COVID-19 outbreaks at nursing care homes in Japan: An ad-hoc survey

Abstract Early detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among individuals in long-term care facilities, such as nursing homes, has the potential to prevent the spread of infection. Polymerase chain reaction testing or antigen screening for SARS-CoV-2 help detect virus carriers; however, non-invasive methods, such as wastewater testing at a facility, might be beneficial as a long-term strategy. Nonetheless, survey studies are limited owing to complications ewrelated to different facilities. Therefore, we conducted an ad-hoc survey in three nursing homes using the grab or trap sampling methods, which have been used in previous studies for environmental surveillance. As this study was conducted on an ad-hoc basis, it is necessary to consider improving the sampling methods for adaptability to different drainage pipe systems across various facilities and ensure the reliability and sensitivity of the detection methods. Nevertheless, the results revealed viral genome detection at the early stage of the outbreak and shedding of the viral genome in the wastewater for approximately two months after the index case. Therefore, the result should be carefully interpreted as the viral genome would be detected over a long period. During the COVID-19 epidemic around the facility, frequent testing of wastewater, especially a combination of other clinical tests where necessary, might be helpful in early confirmation of index cases and reduce the risk of an outbreak within a facility.