Global Prevalence of Asymptomatic Norovirus Infection: A Meta-analysis

Abstract

Background Studies about asymptomatic norovirus infections have been frequently reported. We aim to assess the global prevalence of asymptomatic infections. Method We identified publications that included the proportion of asymptomatic norovirus infections by searching in PubMed, Ovid, Scopus, and Web of Science and by screening references from the articles reviewed. The principal summary data were the prevalence of asymptomatic norovirus infection. Random-effect models for meta-analysis were fitted to generate estimates of overall and subgroup prevalence. Findings Of 81 studies included, asymptomatic norovirus prevalence was estimated at 7% (95% CI: 6%–9%). Africa, Meso America and South America had higher prevalence (15%, 14%, 11%, respectively) while the prevalence in Europe and North America was lower (4%). Prevalence was similar between community and hospital (9%). Prevalence was higher in children (8%) than adults (4%). For food handlers, prevalence was estimated at 3%. In context of outbreaks, prevalence estimated from 15 studies was as high as 18% (95% CI: 10%–30%). Interpretation This knowledge could have an impact on the development of transmission prevention strategies in the future. The high prevalence indicated asymptomatic individuals must not be overlooked. Outstanding questions The high prevalence indicated asymptomatic individuals must not be overlooked. Asymptomatic individuals may play an important role in norovirus transmission. This knowledge could have an impact on the development of transmission prevention strategies.

Diversity of Noroviruses throughout Outbreaks in Germany 2018

“…It is known that norovirus outbreaks can be linked via asymptomatic patients. A meta-analysis of the global distribution of asymptomatic norovirus infections revealed that the prevalence rate in Europe was 18% (95% CI: 10–30%), when asymptomatic individuals were exposed under outbreak circumstances [ 29 ]. It has been discussed that GII.4 variants might originate from immunocompetent humans by inter-host transmission and the accumulation of mutations during the intra-variant periods [ 10 ].…”

Use of Human Intestinal Enteroids to Detect Human Norovirus Infectivity

“…HIE infection can now be used to reevaluate archived samples to better define parameters that would correlate with the infectious period of norovirus gastroenteritis to guide infection control. Of note, in a meta-analysis, the prevalence of norovirus RNA shedding from asymptomatic patients was estimated to be ≈9% ( 9 ). Moreover, in a large-scale study of outbreak data from CaliciNet (https://www.cdc.gov/norovirus/reporting/calicinet/index.html), a national norovirus surveillance network in the United States, the median C t value among asymptomatic patients was 28 ( 10 ).…”

Norovirus transmission mediated by asymptomatic family members in households

“…However, our results suggest the necessity of further analyzing the role of asymptomatic individuals in a community. Since the frequency of asymptomatic infection varies depending on the setting [5,12], analyses of individuals who are selected with an appropriate procedure with less bias are needed to verify the involvement of asymptomatic carriers in the latency and spreading of NV in the district and other settings.…”

“…Epidemiological studies have indicated that there are two NV-infected populations: one is AGE patients, and the other is individuals without diarrheal symptoms. The latter population, called "asymptomatic carriers" (which includes both pre-and post-disease-onset cases), is common worldwide [5,12]. The ratio of asymptomatic NV infections ranges from <1% to >30%, depending on the setting [5,12].…”

“…The latter population, called "asymptomatic carriers" (which includes both pre-and post-disease-onset cases), is common worldwide [5,12]. The ratio of asymptomatic NV infections ranges from <1% to >30%, depending on the setting [5,12]. Asymptomatic NV infection occurs in all age groups, including children and infants [13][14][15][16][17][18][19][20][21].…”