Human metapneumovirus associated acute respiratory infections burden in older adults globally

Background: The human metapneumovirus (hMPV)- associated disease burden in older adults remains under-researched. This review aimed to systematically estimate the global burden of hMPV-associated disease in older adults. Methods: We searched Medline, Embase, Global Health, CINAHL, Web of Science, and Global Index Medicus in February 2023, November 2023 and October 2024; and CNKI, Wanfang and CQVip in April 2024 and October 2024. We included studies conducted over ≥12 consecutive months, reporting on adults aged ≥60 years, and with laboratory-confirmed hMPV infections. Critical appraisal of included studies was conducted using the Joanna Briggs Institute critical appraisal tools. Random effects meta-analyses were conducted to estimate the pooled hMPV proportions positive in acute respiratory infections (ARIs). Using Monte Carlo simulation, we estimated the hMPV-associated hospitalisations globally, in high-income countries, low-and-middle-income countries and the USA in ≥65 years during 2019 as most studies reported on this age group. The hMPV-associated ARI incidence in countries other than the USA and outpatient/ community settings in the USA was summarised narratively. The review protocol was registered on PROSPERO (CRD42023422325). Findings: Forty-six studies conducted between 2005 and 2023, and reporting on hMPV proportion positive estimates (n=36, with 29,866 laboratory tests), hospitalisation rate in the USA (n=4), and hMPV incidence (n=6) were included. We estimated 473,000 (95% confidence interval [CI]: 396,000; 777,000) hMPV-associated hospitalisations globally, 185,000 (105,000; 340,000) in high-income countries (n=6), and 288,000 (193,000; 436,000) in low-and-middle-income countries (n=10) in people aged ≥65 years during 2019. In the USA, the pooled hMPV-associated hospitalisation rate (n=4) was 231 (95% confidence interval [CI]: 41; 421) per 100,000 persons in those aged ≥65 years, representing approximately 122,000 (41,000; 398,000) hospital admissions in this population during 2019. Interpretation: hMPV-associated ARIs contribute to a significant disease and hospitalisation burden in older adults. However, large-scale surveillance studies with more investment in research and diagnostic methods to develop reliable estimates are required.