BACKGROUND: Human metapneumovirus (hMPV) is an increasingly recognized respiratory pathogen in immunocompromised patients, but its impact in haematological malignancies is poorly defined. Unlike influenza or SARS-CoV-2, hMPV has no specific treatment or vaccine, contributing to underdiagnosis and underestimation of its clinical relevance.

METHOD: We performed a multicentre retrospective cohort study within the Epidemiology of COVID-19 in patients with hematological malignancies: A European Haematology Association Survey/ Epidemiology of respiratory viral infections in patients with hematological malignancies: A European Haematology Association Survey registry of haematological patients with hMPV (January 2023-December 2024), comparing clinical features and outcomes with matched influenza and SARS-CoV-2 cohorts.

RESULTS: The study included 130 patients with hMPV. Median age was 58.5 years; 57% were male. Plasma cell neoplasms (25%), lymphoma (23%), and acute myeloid leukemia (20%) were the most common hematological malignancies. Hospitalization occurred in 64%, intensive care unit (ICU) admission in 19%, and 30-day mortality was 8%. Most cases (73%) received supportive care only. Secondary infections were common (24%). Chronic renal disease significantly increased mortality risk (hazard ratio 20.9 11.05, P = .014). Compared with influenza and SARS-CoV-2, hMPV patients had comparable severity and outcomes, with 18.5% ICU admission rates versus 25.9% for influenza ( P = .316) and 20.9% versus 4.7% for SARS-CoV-2 ( P = .006), and 30-day mortality of 5.6% versus 11.1% for influenza ( P = .489) and 7.0% versus 2.3% for SARS-CoV-2 ( P = .277), yet received fewer targeted interventions.

CONCLUSIONS: hMPV causes clinically significant disease in patients with hematological malignancy, often necessitating hospital and ICU care, and leading to mortality. In the absence of specific treatments or vaccines, this virus remains an underrecognized pathogen in patients with hematological malignancy. Enhanced clinical awareness and investment in diagnostics, prevention, and therapeutics are needed.