INTRODUCTION
Human metapneumovirus (hMPV), is a viral respiratory pathogen of global importance 1–4. First identified in 2001, hMPV is a single-stranded negative-sense RNA Pneumovirus which, based on serologic studies, has circulated worldwide in human populations for at least seven decades 5. HMPV is divided into two genetic groups: A and B which are further differentiated into 6 known lineages A1, A2a, A2b, A2c, B1, and B2 6–8 and infects all ages, with severe events occurring in children, the elderly, and the immunocompromised 9. In children, hMPV is pervasive in early-life, causing both upper 10 and severe lower respiratory infections 1,11. Indeed, most children are seropositive for hMPV by age five 5,11–13. Severe hMPV infection is also an important cause in respiratory-associated childhood hospitalization and has globally been estimated to account for 4-18% of Acute Lower Respiratory Infection (ALRI) hospital admissions2,14,15.
Despite the importance of hMPV as a childhood respiratory infection, key questions regarding incidence, severity, and seasonality of hMPV infections particularly in Lower- and Middle-Income Countries (LMIC) remain. Globally, there is significant variation in seasonality of hMPV by location, and hMPV infections can occur throughout the year3,16. Re-infection and repeat symptomatic episodes of hMPV in both children and adults have also been noted12,17–19 highlighting the clinical challenge of this ubiquitous pathogen.
Currently no vaccine exists for hMPV. An important step towards this goal is describing the seasonality and burden of hMPV particularly in LMICs. While research on hMPV is increasing, there are few long-standing cohort studies conducted in Central and Latin America3. In this study, we describe the burden, symptomatic incidence rate, reinfection, and seasonality of hMPV among a cohort of children in Managua, Nicaragua. We additionally describe estimates of effective reproduction numbers for each of the epidemic peaks observed from 2011–2016.