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Norovirus is a substantial public health burden, yet surveillance is challenging because infections are underreported. Wastewater surveillance offers a complementary approach. We quantified norovirus genogroups GI and GII from 2,823 wastewater samples collected in New York, USA, during September 2022–July 2024. Across 4 counties in New York, we detected norovirus GI in 100% of samples and GII in 92%–100%. Both genogroups exhibited strong seasonal trends. During the study period, 499 norovirus-specific and 50,004 all-cause acute gastroenteritis hospitalizations occurred. Weekly correlations between GII concentrations and norovirus-specific hospitalizations showed moderate positive relationships (ρ = 0.23–0.28); GI concentrations showed weak correlations (ρ = −0.18 to 0.06). Correlations between norovirus in wastewater and all-cause acute gastroenteritis hospitalizations were weaker. Although wastewater surveillance reliably detects seasonal norovirus circulation in the population, correlations with hospitalizations were moderate. GII showed stronger associations with clinical outcomes than GI, supporting the importance of genogroup-specific monitoring.
Noroviruses are genetically diverse icosahedral viruses belonging to the family Caliciviridae; they consist of a single-stranded, positive-sense RNA genome. They are a leading cause of diarrheal disease. and can infect a wide variety of hosts ( 1 ). Norovirus consists of 10 genogroups (GI–GX) and 49 genotypes. Genogroups GI, GII, GIV, GVIII and GIX are known to infect humans, whereas genogroup GIII primarily infects cows and GV mice ( 1 – 4 ). Norovirus infections are highly contagious, causing gastroenteritis that is typically mild and self-limiting in healthy adults but can be severe and even fatal in children, elderly, and immunocompromised persons. In the United States, outbreaks peak during November–April ( 5 , 6 ) and cause $2.3 billion in direct medical costs and $1.4–$20.7 billion in loss of productivity annually ( 7 ).
As of August 2026, norovirus surveillance relies primarily on either outbreak detection with case investigations or individual case reporting. Most norovirus infections in healthy adults are either asymptomatic or self-limiting and thus not tested, leading to a large burden of unreported incidence ( 1 , 8 , 9 ). In most US jurisdictions norovirus is not a notifiable disease. Poor clinical surveillance provides inaccurate estimates of norovirus incidence, which leads to lower prioritization for prevention and control. Understanding the true epidemiologic burden of norovirus requires an approach that addresses those limitations. Wastewater surveillance is one potential data source; it does not depend on symptomatic persons seeking medical care but enables community-level infectious disease surveillance ( 10 ).
The level of norovirus RNA in wastewater has been associated with the monthly incidence of acute gastroenteritis hospitalizations across diverse geographic regions ( 11 ). Several studies have found a strong correlation between norovirus genogroup–spec…