Norovirus can be accurately tracked in wastewater samples, which can help identify outbreaks and trends, according to a new study based on California wastewater surveillance published in Emerging Infectious Diseases.
Norovirus is one of the leading causes of gastroenteritis in the United States, but surveillance is challenging because many cases are unreported, the authors said. As wastewater surveillance has proved useful and accurate for viral detections, including COVID-19, the researchers assessed its usefulness for norovirus.
The authors collected wastewater data from December 17, 2022, through December 17, 2023, from 76 California wastewater utilities, as part of the WastewaterSCAN program.
The authors looked for norovirus viral RNA from wastewater samples and compared findings with Centers for Disease Control and Prevention National Respiratory and Enteric Virus Surveillance System (NREVSS) norovirus test positivity at the national and western US regional level.
Activity peaked in Southern California in February
That data was then cross-referenced with California Norovirus Laboratory Network (NLN)–confirmed GII norovirus outbreaks, which are published monthly.
"We observed positive, statistically significant (p<0.001), moderate-to-strong correlations between California regional and statewide wastewater aggregates and US national and western regional NREVSS test positivity," the authors said.
The authors said they observed distinct regional patterns to norovirus outbreaks in the state, with activity peaking February 22, 2023, in Southern California, and March 24, 2023, in the San Joaquin Valley.
Given that no other local California norovirus surveillance data are available, wastewater data have been used as a local and leading indicator to support investigations of gastrointestinal illness outbreaks.
"Given that no other local California norovirus surveillance data are available, wastewater data have been used as a local and leading indicator to support investigations of gastrointestinal illness outbreaks," the authors concluded. "Those data have enabled LHDs [local health departments] to more (or less) aggressively pursue investigation and control efforts during gastroenteritis outbreaks, efforts that are time- and resource-intensive for LHDs, the public, and affected establishments."