Genotype-resolved wastewater surveillance for monitoring human norovirus GII circulation

Norovirus GII causes a substantial global burden of acute gastroenteritis, and genotype-resolved wastewater surveillance offers a complementary approach for monitoring community circulation beyond cases captured by routine clinical surveillance. We monitored four municipal wastewater treatment plants in Beijing, China, from October 2023 to September 2024 and compared weekly GII genotype profiles with contemporaneous sporadic-case and outbreak surveillance. Strict-weekly genotype comparisons were the primary inference and used moving-block bootstrap confidence intervals, block-sign tests, and false-discovery-rate correction; centred 3-week profiles were used for description and sensitivity analysis. Bray-Curtis dissimilarity quantified compositional concordance, and same-week and lagged Spearman correlations compared wastewater GII concentration with clinical surveillance activity. In the centred 3-week wastewater series, GII.4 had the highest mean read-based relative abundance (31.1%), followed by GII.17 (17.5%) and GII.7 (15.2%). In strict-weekly comparisons, wastewater had lower GII.17 representation than sporadic cases (-32.6 percentage points) and lower GII.7 representation than outbreaks (-14.0 percentage points). Wastewater had higher GII.3, GII.4, GII.6, and GII.9 representation than sporadic cases and higher GII.9 and GII.13 representation than outbreaks; the GII.4 and GII.7 differences were sensitive to analytical specification, and the GII.13 effect was small. Mean strict-weekly Bray-Curtis dissimilarities were 0.590-0.679 in 32 common weeks. Same-week and lagged wastewater concentration correlations with sporadic-case positivity and outbreak case counts were not significant after temporal-dependence and multiplicity correction. Genotype-resolved wastewater surveillance documented co-circulating GII genotypes and recurrent source-specific differences, while read-based relative abundance remained dependent on catchment coverage and genotype-specific analytical performance.