Assessing indicators of severe human metapneumovirus respiratory tract infections in children

<bold>Background:</bold> Human metapneumovirus (hMPV) is an important pathogen that causes both upper (URTI) and lower respiratory tract infections (LRTI) in children. The virus can be implicated in severe bronchiolitis and pneumonia, necessitating hospitalization, with certain cases requiring intensive care unit intervention. <bold>Methods:</bold> As part of a retrospective observational study, we aimed to identify indicators of severe hMPV respiratory tract infections in children referred to the University Children's Hospital Ljubljana and the Department of Infectious Diseases Ljubljana, Slovenia, during a recent outbreak. We analyzed clinical data from November 2022 to January 2023 and compared the characteristics of children presenting with URTI and LRTI. We also examined the characteristics of children with hMPV LRTI, distinguishing between children with and without LRTI-associated hypoxemia. <bold>Results:</bold> Of 78 hMPV-PCR-positive pediatric patients (mean age 3.1 years; 60.3% boys), 36% had a URTI, and 64% had an LRTI. Hospitalization was required in 64% (50/78), with 42% (21/50) requiring oxygen therapy. LRTI-associated hypoxemia was more common in patients with atopy who showed dyspnea, tachypnea, crackles, and wheezing on lung auscultation. In a multivariable logistic regression analysis, obstructive lung auscultation was a significant predictive factor for hypoxemic hMPV-LRTI, with children with wheezing ten times more likely to have hypoxemia. Prematurity and chronic conditions did not influence the presentation or severity of hMPV infection. <bold>Conclusion:</bold> This study highlights wheezing and atopy as crucial indicators of severe hMPV LRTI in children, emphasizing the importance of early recognition and intervention.