Decade of Hangzhou data shows rotavirus shifts and myocardial injury signal

A ten-year retrospective study from a single hospital in Hangzhou, China, has documented how the epidemiology of rotavirus infection in children was reshaped around the COVID-19 pandemic, and reports an exploratory association between rotavirus positivity and physician-documented myocardial injury in the later phases of that period. The analysis, published in Gut Pathogens as an open-access research article, drew on 71,115 rotavirus antigen test-episodes from children aged 15 years or younger who presented with acute diarrhoea between January 2016 and December 2025. The investigators followed STROBE-RECORD reporting guidelines for electronic-health-record-based observational research and included both inpatients and outpatients. Duplicate tests within a single diarrhoeal episode were excluded, while distinct episodes separated by more than 14 days in the same child were retained.

Overall rotavirus test-positivity was 16.25 percent, with 11,553 of the 71,115 test-episodes returning a positive result. Positivity peaked at one year of age, reaching 23.91 percent in that group, and one-year-olds accounted for 43.31 percent of all rotavirus-positive test-episodes. The annual trajectory was striking: positivity peaked at 44.55 percent in 2017, fell to a nadir of 2.80 percent in 2023, rebounded to 9.02 percent in 2024, and modestly declined to 8.51 percent in 2025. When the decade was divided into three periods, positivity declined stepwise from 27.55 percent pre-COVID (2016 to 2019) to 10.16 percent mid-COVID (2020 to 2022) and 6.82 percent post-COVID (2023 to 2025), a difference the authors report as highly significant.

The pandemic-era decline was not uniform across ages. The authors state that the age-stratified changes were compatible with shifts in age-specific population susceptibility: larger declines were observed in toddlers, whereas changes were modest in school-aged children, with a negative rank correlation between age and the magnitude of decline. Consistent with this, the median age of rotavirus-positive children rose across periods, from 1.0 year pre-COVID to 2.0 years mid-COVID and 3.0 years post-COVID. The proportion of rotavirus-positive children aged two years or older climbed from 48.2 percent before the pandemic to 76.5 percent after it. The study period coincided with the COVID-19-associated non-pharmaceutical interventions that the authors note profoundly altered enteric virus circulation, and the data are presented as observational and compatible with these age-distribution shifts rather than as proof of causation.

Seasonality also appears to have been reshaped. Negative-binomial regression applied to monthly aggregated counts showed a significant month-by-period interaction, which the authors interpret as consistent with a change in seasonal pattern: the pre-COVID winter-early-spring peak was attenuated during the mid-COVID period and shifted toward a spring-centred peak in the post-COVID years. Cosinor-harmonic regression, an alternative approach to formal seasonal inference, failed to converge and was not used. The authors emphasize that these are descriptive and model-based observations from a single centre, and that continuous epidemiological surveillance remains warranted to track whether the altered age distribution and seasonal timing persist.

The study’s most cautionary finding concerns the heart. Physician-documented myocardial injury, extracted from electronic medical records as diagnostic labels obtained within three days of rotavirus testing, occurred in 1.13 percent of rotavirus-positive test-episodes compared with 0.42 percent of rotavirus-negative episodes, yielding a crude relative risk of 2.67. Stratified by period, the crude relative risk was 1.51 and not statistically significant pre-COVID, but rose to 6.29 mid-COVID and 5.93 post-COVID, with a statistically significant period-by-rotavirus-status interaction. No physician-documented myocardial injury was recorded among rotavirus-positive infants younger than one year, and age-specific myocardial-injury proportions among rotavirus-positive children did not increase monotonically with age. The authors stress that this analysis is exploratory because universal standardized cardiac screening was not implemented across the cohort, and they interpret the data as showing an association with elevated risk of physician-diagnosed myocardial injury in mid- and post-COVID periods, whereas no statistically significant association existed pre-pandemic.

The findings carry substantial retrospective limitations that the authors set out explicitly. Unique patient identifiers were not retained in the frozen analytical dataset, so patient-level clustering could not be performed and repeated test-episodes may have inflated the statistics. Electrolyte abnormality labels were unavailable and cardiac testing frequency could not be quantified, precluding adjustment for electrolyte disturbances and precise assessment of surveillance bias. Reagent and assay documentation was incomplete. Sensitivity analyses, including a hospitalized-only subset and models incorporating available comorbidity diagnostic tags, together with Firth penalized logistic regression for sparse-event strata, are provided in supplementary tables. Given these constraints, the authors suggest increased clinical awareness for potential cardiac complications in hospitalized rotavirus-positive children rather than drawing firm causal conclusions, and they recommend ongoing surveillance of paediatric rotavirus epidemiology as circulation patterns continue to evolve after the pandemic era.

Subject of Research: Epidemiology of paediatric rotavirus infection and physician-documented myocardial injury in Hangzhou, China, 2016–2025

Article Title: Epidemiologic shifts, seasonal reshaping, and exploratory analysis of physician-documented myocardial injury in children with rotavirus infection in Hangzhou, China, 2016–2025: a decade-long single-centre retrospective study

Article References: Xu, X., Zhao, W., Wang, J., Zhao, X., & Lin, X. (2026). Epidemiologic shifts, seasonal reshaping, and exploratory analysis of physician-documented myocardial injury in children with rotavirus infection in Hangzhou, China, 2016–2025: a decade-long single-centre retrospective study. Gut Pathogens. https://doi.org/10.1186/s13099-026-00890-w

Image Credits: AI Generated

DOI: 10.1186/s13099-026-00890-w

Keywords: rotavirus, myocardial injury, children, COVID-19, epidemiology, seasonality, Hangzhou, retrospective study, Epidemiologic, shifts, seasonal, reshaping