Disease Spectrum of Human Metapneumovirus Infections in Infants and Young Children: Data From a Prospective Multicenter Study in Germany

Background: Human metapneumovirus (hMPV) is a significant respiratory pathogen in infants and young children. Although most infections present as nonsevere cases in outpatient settings, severe courses can lead to hospitalization. Few potential risk factors for hospitalization have already been identified, but studies comparing the clinical presentation of children with hMPV in inpatient versus outpatient settings are lacking. Methods: This retrospective analysis used data from the Pediatric Airway Pathogen Incidence study, a multicenter surveillance study of lower respiratory tract infections, conducted in Germany during winter seasons 2021/22 and 2022/23 (weeks 40–17 each season). We compared 102 hospitalized and 114 outpatient pediatric cases with laboratory-confirmed hMPV infection after excluding coinfections with respiratory syncytial virus. Detailed clinical and demographic data were collected. Results: Hospitalized patients were significantly younger (median age 9 vs. 14 months, P = 0.003) than outpatients. Prematurity was notably higher in severe cases (25% vs. 6.2%, P < 0.001), and extreme prematurity (gestational age <28 weeks) was present only in hospitalized patients. Hospitalized cases were independently associated with a history of recurrent wheezing, but not with neonatal invasive and noninvasive respiratory support, inhalative steroids and bronchopulmonary dysplasia. On clinical examination, hospitalized children more often exhibited wheezing, crackles, tachypnea, hypoxemia and reduced fluid intake. Hypoxemia in hMPV was independently associated with gestational age at birth, but not with age at diagnosis. Conclusion: The clinical presentation of hMPV in hospitalized young children differed from that observed in outpatient settings. We identified multiple factors that were independently associated with hMPV-related hospitalization.