Human Metapneumovirus Infections in Young and Elderly Adults

Human metapneumovirus virus (hMPV) is a newly discovered respiratory pathogen with limited epidemio-logical data available. Cohorts of young and older adults were prospectively evaluated for hMPV infection during 2 winter seasons. Patients hospitalized for cardiopulmonary conditions during that period were also studied. Overall, 44 (4.5%) of 984 illnesses were associated with hMPV infection, and 9 (4.1%) of 217 asymp-tomatic subjects were infected. There was a significant difference in rates of hMPV illnesses between years 1 and 2 (7/452 [1.5%] vs. 37/532 [7.0%];). In the second year, 11 % of hospitalized patients had evidenceP!.0001 of hMPV infection. Infections occurred in all age groups but were most common among young adults. Frail elderly people with hMPV infection frequently sought medical attention. In conclusion, hMPV infection occurs in adults of all ages and may account for a significant portion of persons hospitalized with respiratory infections during some years. Human metapneumovirus virus (hMPV) is a newly discovered human respiratory pathogen [1]. Geneti-cally, hMPV is similar to avian pneumovirus and has been classified in the subfamily Pneumovirinae, genus Metapneumovirus [2]. The virus was first isolated in The Netherlands from 28 young children with illnesses similar to human respiratory syncytial virus (hRSV) infections. Isolation of the virus in cell culture requires prolonged incubation, and identification is difficult when traditional techniques are used. Sequence studies of isolates have identified 2 main lineages of hMPV