Prevalence and seasonality of norovirus in agricultural irrigation water across China: implications for food safety

Norovirus (NoV) is a leading cause of acute gastroenteritis worldwide. Irrigation water has been confirmed as a vector for transmitting NoV to crops. The study aimed to analyze the prevalence of NoV in irrigation water across China and assess its implications for food safety. Between December 2023 and April 2024, 200 irrigation water samples were collected from 27 cities. Viral concentration was performed using tangential flow filtration, followed by RNA extraction and RT-qPCR detection for NoV genogroups GI and GII. NoV was detected in 17 samples (8.50%, 17/200). Among the positive samples, GI was identified in 8 (4.00%), GII in 14 (7.00%), with 5 samples (2.50%) positive for both genogroups. The results indicated that the detection rate of NoV in irrigation water exhibited seasonal variation, with a significantly higher rate observed in winter compared to spring ( p < 0.001). Irrigation water in China is a reservoir for NoV, with a significantly higher contamination level in winter. These findings highlight irrigation water as a potential risk factor for foodborne and waterborne NoV transmission and warrant focused attention in public health strategies.