Asymptomatic norovirus infection during outbreaks in China: A systematic review and meta-analysis.

Acute gastroenteritis outbreaks may be caused by the excretion of norovirus (NoV) from asymptomatic individuals. Despite numerous studies involving asymptomatic NoV infection during outbreaks in China, a comprehensive assessment of its role has not been conducted, which is critical for emergency management. Our objective was to assess the prevalence of asymptomatic NoV infection during outbreaks in China. We conducted a comprehensive search of multiple databases, including PubMed, Web of Science, Cochrane Library, China National Knowledge Infrastructure, China Wanfang, and China Weipu, between January 1, 1997 and June 19, 2023. The retrieved articles and their references underwent screening, which utilized polymerase chain reaction-based assays for the detection of NoV in asymptomatic individuals during outbreaks that occurred in China. The primary summary data were the prevalence of asymptomatic NoV infection in outbreaks. We generated pooled estimates of asymptomatic prevalence in the population as a whole and in subgroups by using random-effect models. Of the 97 articles included, the pooled asymptomatic prevalence of NoV among 5117 individuals in outbreaks was 17.6% (95% confidence interval [CI]: 14.1-21.3). The asymptomatic prevalence of NoV GII (17.1%, 95% CI: 12.9-21.5) was similar to that of NoV GI (22.0%, 95% CI: 12.8-32.4). However, the proportion of asymptomatic individuals involved in NoV GII (57.44%) was significantly higher than that of NoV GI (5.12%), and NoV GII (75.26%) was reported much more frequently than NoV GI (14.43%) in the included articles. Meta-regression analysis of 11 possible influencing factors (geographic region, setting, season, sample type, genotype, transmission route, occupation, age, per capita income, study quality, and cases definition) showed that the source of heterogeneity might be related to the outbreak settings, per capita income, and study quality (p = 0.037, 0.058, and 0.026, respectively). Of particular note was the asymptomatic prevalence peaked in preschoolers (27.8%), afterward, it fell into trough in elementary and junior school children (10.5%), before the second peak located in adults (17.8%), and the elderly (25.2%). Prevalent genotypes reported include GII.4, followed by GII.17, GII.2, GII.3, GII.6, and so forth. The estimated asymptomatic prevalence of NoV during outbreaks in China was as high as 17.6%, with NoV GII dominating. In addition, genetic subtypes of NoV in outbreaks should be detected whenever possible. The role of asymptomatic individuals in NoV outbreaks cannot be ignored. This knowledge will help governments develop public health policies and emergency response strategies for outbreaks, assess the burden, and develop vaccines.

[Analysis on neutralization antibody titer of Japanese B encephalitis virus in healthy population in Shaanxi province].

OBJECTIVE: To detect Japanese B Encephalitis virus (JEV) neutralization antibody (NA) titer and evaluate immunologic barrier, analyze the factor of affecting JEV NA titer, and provide the data for JE control. METHOD: Cluster sampling was selected randomly in the region of high, middle, low JE incidence rate. To detect the NA of JEV by micro neutralization test. RESULTS: The positive rate of JEV NA (and GMT) was 81.3% (1:27.84) in Ankang prefecture where JE incidence rate was high, 47.9% (1:7.41) in Baoji prefecture where JE incidence rate was middle, 24.1% (1:3.04) in Tongchuan prefecture where JE disease rate was low. There was the tendency that JEV NA titer increased with increasing age in the region of high JE disease rate, and there was not this tendency in the region of low JE incidence rate. CONCLUSION: In shaanxi province, the children's JEV NA titer was low in the region of high JE incidence rate, and it is important to vaccinate JE vaccine for children. The adult's JEV NA titer was low in the region of low JE incidence rate. And it is important to control JE disease in adult groups.

[Analysis on data from the clinical acute viral encephalitis surveillance system in three prefectures in Shaanxi during 2005 - 2006].

OBJECTIVE: To describe the epidemiological features of viral encephalitis and burden of Japanese encephalitis (JE), and to identify potential strategies for effective JE control measures, using data from the Viral Encephalitis Surveillance Program (VESP) launched in Ankang, Baoji, and Weinan prefectures, Shaanxi province. METHODS: Data was gathered from sentinel hospitals reporting system on all the viral encephalitis (VE) cases identified between June 2005 and May 2007. County Center for Disease Control and Prevention (CDC) investigated the cases, drawing blood and cerebrospinal fluid (CSF) samples from the hospitals, and testing IgM antibody against JE using ELISA. We used Epi Data and Excel for data entry and analysis. RESULTS: A total of 1097 VEs were reported and 1053 (96.0%) had blood or CSF samples collected and tested for IgM antibody against JE. Three hundred and eleven cases (29.5%) showed JE antibody positive (JE confirmed case). Among the JE confirmed cases, numbers of those under 15 year of age accounted for 33.7%, 43.9% and 88.3% in Baoji, Weinan and Ankang prefectures respectively. The rest were mainly children aged 5-14 years old (53.3%). Toddlers,farmers and children accounted for 85.2% in JE confirmed cases. About half of other VE cases (51.0%) were students of all age. Data an investigation on 398 reported VE cases at discharge, showed that 67.1% of JE confirmed cases recovered while 83.7% of the other VE cases fully recovered. The case fatality rates were 9.2% for JE confirmed cases and 3.1% for other VE cases. 578 cases were followed up at 90-days after discharge, 69.6% of JE confirmed cases and 90.2% of other VE cases recovered, with case fatality rates were 13.6% and 3.6% for JE confirmed cases and for other VE cases, respectively. The sequelae rates were 10.0% for JE confirmed cases and 4.5% for other VE cases. CONCLUSION: The peak of the VE season was the same as that of JE. There were 45.6% of reported JE cases with negative JE IgM, suggesting that it is necessary to carry out laboratory testing for clinical diagnosis cases. The fact that high risk population was different at prefectures levels suggested that more attention be paid in JE control and prevention.