Respiratory tract infection due to human metapneumovirus among elderly patients.

After the initial isolation of human met-apneumovirus (hMPV) from infants with respiratory tract illnesses (RTIs), a pleth-ora of studies involving the pediatric population have demonstrated that, in this population, hMPV infection accounts for 5%–25% of reported RTIs. Among infants hospitalized for RTI, hMPV is often the second most detected pathogen after human respiratory syncytial virus (hRSV). The clinical signs induced by both infections in patients of all ages are similar and range from mild upper RTI to bronchi-olitis and pneumonia. Primary infection with hMPV does not induce lifelong immunity ; several studies have shown that reinfection can occur during adult life, possibly because of waning immunity. Studies among adults have shown that clinical signs related to reinfection are usually restricted to the upper respiratory tract, but respiratory viruses, such as hMPV, hRSV, and influenza virus, have been associated with influenza-like illness, bronchitis, pneumonia, and exacerbations of both asthma and chronic obstructive pulmonary disease in the adult population [1]. This was illustrated in a study among patients of all ages, where Boivin et al. [2] detected hMPV not only in young children with RTI but also in immunocom-promized individuals, adults, elderly adults, and institutionalized elderly adults. In adults with underlying disease, in particular , it has been demonstrated that hMPV is a major causative agent of RTI and, in some cases, is associated with fatal outcomes. Only limited studies of hMPV infection, mostly case reports, are available involving elderly adults or institutionalized elderly adults. Honda et al. [3] described the occurrence of hMPV infection in a hospital for older people in Japan. Eight of 23 patients (age range, 65–89 years) in 1 ward who shared the same day care room were infected with hMPV, and all patients recovered. Kaye et al. [4] detected 20 samples that were positive for hMPV out of 373 total samples obtained in an adult hospital (patient age 118 years); 10 of these samples were obtained from patients who were 175 years old. In addition, in the 2 years of this study, hRSV and hMPV were each responsible for as many hospitalized cases of RTI as was influenza virus. Among 741 samples obtained from patients 118 years old, O'Gorman et al. [5] detected 6 hMPV-positive samples. All 6 patients were aged 150 years (range, 51– 83 years); 2 were hospitalized inpatients with chronic obstructive pulmonary disease , and 2 of the patients, both of whom died, received …