Prevalence of Infections in Thailand and Its Association with HIV and Diarrhea: A Systematic Review and Meta-Analysis.

is a protozoan parasite and a major cause of diarrhea, especially in children and immunocompromised individuals. Despite evidence of its presence in Thailand, comprehensive national data remain limited. This systematic review and meta-analysis aimed to estimate the prevalence of infection in Thailand and assess its association with diarrhea, especially among vulnerable populations, to support targeted public health strategies. This systematic review followed the PRISMA guidelines and was registered with PROSPERO (CRD420251015538). A systematic search was conducted in PubMed, Embase, Scopus, Journals@Ovid, Nursing & Allied Health Premium, Google Scholar, and the Thai-Journal Citation Index (TCI) to identify studies on infections in humans in Thailand. Quality assessment was independently performed using Joanna Briggs Institute tools. Pooled prevalence and odds ratios (ORs) were estimated using random-effects meta-analyses. Heterogeneity was explored via meta-regression and subgroup analyses, and publication bias was assessed using funnel plots and Egger's test. A total of 38 studies with 24,759 participants were included, mostly conducted in Central Thailand. The pooled prevalence of infections was 4.70% (95% CI: 2.68-8.13%), with the highest prevalence observed in Northern Thailand (11.14%) and among HIV-infected individuals (16.33%). Significant predictors of higher prevalence included region, age group, participant type, and diarrheal status. Infection was associated with a non-significant two-fold increased odds of diarrhea (: 0.39; OR: 2.00; 95% CI: 0.67-5.99), but significantly higher odds of diarrhea among patients with infections were seen in the Central region (OR: 3.71; 95% CI: 1.17-11.8). HIV-seropositive individuals had a significantly higher risk of infection (: 0.006; OR: 8.15; 95% CI: 1.82-36.50). This systematic review and meta-analysis estimated a pooled prevalence of infections in Thailand of 4.70%, with the highest rates in Northern Thailand (11.14%) and among HIV-infected individuals (16.33%). Although infection was associated with a two-fold increase in the risk of diarrhea, the association was not statistically significant. Notably, HIV-seropositive individuals had an eight-fold higher risk compared to HIV-seronegative individuals. Future research should expand surveillance in under-represented regions to better understand the epidemiological burden and guide public health interventions.