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

Background Human metapneumovirus (HMPV) is a prevalent respiratory pathogen, but comprehensive estimates of severe clinical outcomes across populations are lacking. We synthesized the proportion of severe outcomes among people with laboratory-confirmed HMPV infection. Method We searched PubMed, Embase, Web of Science, Scopus, Cochrane Library, medRxiv, bioRxiv, and Google Scholar from inception to 20 January 2026, without language restrictions. Observational studies reporting severe outcomes (hospitalization, intensive care unit [ICU] admission, respiratory support, mechanical ventilation, mortality) in laboratory-confirmed HMPV infection were eligible; studies enrolling only people who are immunocompromised 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. Results Ninety-four studies (∼26 000 people who are HMPV positive) were included. Pooled proportions were 48% (95% CI, 20%–78%; 8 studies, n = 1445) 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 = 4328) for respiratory support; 8% (95% CI, 5%–13%; 16 studies, n = 5543) 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%). Conclusions Human metapneumovirus causes substantial hospitalization, ICU admission, and mortality, supporting strengthened surveillance, integration into respiratory virus prevention strategies, and accelerated vaccine development.