Systematic Review and Meta-analysis of Clinical Severity and Population-Specific Outcomes of Human Metapneumovirus Infection

Abstract Background Human metapneumovirus (HMPV) is a prevalent respiratory pathogen, but comprehensive estimates of severe clinical outcomes across populations are lacking, limiting evidence-based public health prioritization. We synthesized the proportion of severe outcomes among patients with laboratory-confirmed HMPV infection. Methods We searched PubMed, Embase, Web of Science, Scopus, Cochrane Library, medRxiv, bioRxiv, and Google Scholar from inception to January 20, 2026, without language restrictions. Observational studies reporting severe outcomes (hospitalization, ICU admission, respiratory support, mechanical ventilation, mortality) in laboratory-confirmed HMPV infection were eligible; studies enrolling only immunocompromised patients without comparators were excluded. Two reviewers independently extracted data and assessed quality using Joanna Briggs Institute checklists. Pooled proportions were estimated using random-effects generalized linear mixed models with logit transformation. Subgroup analyses examined healthcare setting and age. Reporting followed PRISMA guidelines. Results Ninety-four studies (∼26,000 HMPV-positive patients) were included. Pooled proportions were 48% (95% CI, 20%–78%; 8 studies, n=1,445) for hospitalization; 12% (95% CI, 8%–16%; 26 studies, n=14,522; Egger P=.03) for ICU admission; 40% (95% CI, 26%–56%; 18 studies, n=4,328) for respiratory support; 8% (95% CI, 5%–13%; 16 studies, n=5,543) for mechanical ventilation; and 3% (95% CI, 2%–5%; 29 studies, n=13,657; I2=78.5%) for in-hospital mortality. Mortality was highest among adults (6%). Sensitivity analyses excluding low-quality studies yielded consistent results. Conclusions HMPV causes substantial hospitalization, ICU admission, and mortality at rates comparable to RSV and influenza, supporting strengthened surveillance, integration into respiratory virus prevention strategies, and accelerated vaccine development.