Rotavirus and Norovirus Infections in Children Under 5 Years Old with Acute Gastroenteritis in Southwestern China, 2018–2020

OBJECTIVE: Rotaviruses and noroviruses are important causes of acute gastroenteritis in children. While previous studies in China have mainly focused on rotavirus, we investigated the incidence of norovirus in addition to rotavirus in Southwestern China. METHODS: From January 2018 to December 2020, cases of rotavirus or norovirus infections among children under five ages with acute gastroenteritis were evaluated retrospectively. RESULTS: The detection rate of rotavirus was 24.5% (27,237/111,070) and norovirus was 26.1% (4649/17,797). Among 17,113 cases submitted for dual testing of both rotavirus and norovirus, mixed rotavirus/norovirus infections were detected in 5.0% (859/17,113) of cases. While there was no difference in norovirus incidence in outpatient compared to hospitalized cases, rotavirus was detected two times more in outpatients compared to hospitalized cases (26.6% vs.13.6%; P < 0.001). Both rotavirus and norovirus infections peaked in children aged 12–18 months seeking medical care with acute gastroenteritis (35.6% rotavirus cases; 8439/23,728 and 32.5% norovirus cases; 1660/5107). Rotavirus infections were frequent between December and March of each year while norovirus was detected earlier from October to December. Our results showed significant correlation between virus detection and environmental factors such as average monthly temperature but not relative humidity. In addition, we observed a reduction in the detection rates of rotavirus and norovirus at the beginning of the SARS-CoV-2 pandemic in 2020. CONCLUSION: Our results indicate that rotavirus and norovirus are still important viral agents in pediatric acute gastroenteritis in Southwestern China.