Abstract
Human metapneumovirus (hMPV) is an important cause of acute respiratory tract infections. This study aimed to describe the clinical characteristics, outcomes, and molecular features of hMPV infection among hospitalized patients in Romania. We performed an analysis of prospectively collected surveillance data from patients hospitalized with influenza-like illness or severe acute respiratory infection and tested by RT-PCR for the presence of respiratory viruses between November 2023 and May 2025. Only cases of hMPV monoinfection were analyzed. Clinical, laboratory, and outcome data were analyzed, and a subset of samples with high viral load underwent genetic sequencing of the hMPV fusion (F) gene. A total of 71 patients met the criteria. Children accounted for 62.0% of cases. The clinical features were nonspecific, dominated by cough (87.3%), fever (80.3%), and nasal congestion (47.9%). Adults were significantly more likely to develop dyspnea and respiratory failure requiring oxygen supplementation (51.9% vs. 6.8%, p < 0.001). The median length of hospital stay was 5 days (interquartile range: 2, 7 days), and dyspnea at admission was the strongest factor associated with prolongation of hospitalization. The rate of intensive care unit admission was 4.2%, and overall outcomes were favorable, with no deaths recorded. Molecular analysis revealed the circulation of different hMPV subclades across consecutive seasons, with A2b1 predominating in 2023-2024 and A2b2 in 2024-2025. hMPV infection in hospitalized patients presents with nonspecific clinical features and shows distinct age-related patterns of severity and complications. Early identification of respiratory involvement, particularly dyspnea at presentation, may support risk stratification and optimized clinical management. Preliminary molecular data indicate dynamic circulation of hMPV subclades, underscoring the value of integrated clinical and molecular surveillance. These findings support the inclusion of hMPV in the differential diagnosis of severe acute respiratory infections and highlight the importance of continued monitoring in the post-pandemic period.