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.