A large multicentre study highlights the impact of human metapneumovirus on elderly Italians.

What is it about?

Human metapneumovirus (hMPV) is a respiratory agent that is one of the most common causes of airway diseases. These diseases can range in severity and affect all age groups, particularly young children and the elderly. A large multicentre study, conducted by La Sapienza University, the University of Milan, and the University of Pavia, collected and analysed data obtained from seventeen AMCLI GLIViRe working group centres throughout Italy between 2022 and 2024. Funded by the National Recovery and Resilience Plan (PNRR) as part of initiatives on emerging infections, the research highlighted the circulation of the virus and its impact on older people. It was published in a supplement of The Journal of Infectious Diseases dedicated entirely to hMPV. Nearly 100,000 respiratory samples from patients of all ages (both outpatients and inpatients) were analysed, revealing an hMPV positivity rate of 3.4%. Among those over 50, positivity was 2.6%, with one-third of cases occurring in individuals over 80 years of age. The results revealed two seasonal peaks of the virus, in February 2023 and April 2024, which, despite some geographical variations, exhibited a similar incidence among the general population and the elderly. In some North-Western areas, hMPV was found more frequently in outpatients than in hospitalised patients. Genetic analysis of viral strains revealed an even distribution of the two main subtypes (hMPV-A and hMPV-B), with an increase in emerging variants and a decrease in previously circulating strains.

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Why is it important?

Studies on SARS-CoV-2 have prompted the surveillance of other respiratory viruses, which are a leading cause of hospitalisation across all age groups. This large, multicentre study sheds new light on the circulation and infection rates of human metapneumovirus (hMPV) in the post-pandemic period. The results clearly show that hMPV is a significant respiratory pathogen, particularly in older adults. This emphasises the need to develop targeted preventive strategies, including vaccines, to safeguard the most vulnerable members of society.