Abstract

Acute gastroenteritis (AGE) represents a significant global health burden, particularly affecting adults in healthcare settings and long-term care facilities. The COVID-19 pandemic dramatically altered the epidemiological landscape of enteric infections through non-pharmaceutical interventions. The post-pandemic era has witnessed an unprecedented resurgence of viral gastroenteritis pathogens, necessitating a comprehensive analysis of temporal trends and clinical outcomes. This systematic review and meta-analysis assessed global trends in adult VGE epidemiology, diagnostics, treatment, complications, and mortality by comparing pre-COVID (2015-2019) and post-COVID (2022-2024) periods. PubMed/MEDLINE, Embase, Cochrane Library, Web of Science, Scopus, and regional databases were searched from January 2015 to December 2024. Observational studies reporting on adults (≥18 years) with confirmed or suspected VGE were included. Risk of bias was assessed using the Newcastle-Ottawa Scale and JBI Critical Appraisal Checklist. Random-effects meta-analysis was conducted using the DerSimonian-Laird method. A total of 127 studies encompassing 2,847,392 adult patients from 42 countries were included. Norovirus outbreak incidence increased by 96% in the 2024-2025 season compared to pre-pandemic levels (2,407 vs. 1,230 outbreaks; p < 0.001). Multiplex PCR adoption enhanced diagnostic sensitivity from 56-78% to 98.5% (pooled difference: 28.4%, 95% CI: 22.1-34.7%) while reducing hospital length of stay by 60% (mean difference: -4.5 days). Mortality risk remained elevated in adults aged ≥65 years (RR: 21.8, 95% CI: 18.2-26.1). Turkish data revealed a genotype shift from GII.4 to GII.17 and case fatality rates of 0.4-1.8%. The post-COVID era demonstrates VGE resurgence exceeding pre-pandemic levels. Advances in molecular diagnostics have improved clinical outcomes through rapid pathogen identification. Elderly populations remain disproportionately affected, emphasizing the need for targeted prevention strategies and vaccine development. Study limitations include significant heterogeneity (I²: 72-89%) and predominance of high-income country data.

Key words: Viral gastroenteritis, Norovirus, COVID-19 pandemic, Epidemiology, Multiplex PCR, Mortality, Türkiye, Systematic review, Meta-analysis, PRISMA 2020