The emergence, impact, and evolution of human metapneumovirus variants from 2014 to 2021 in Spain.

Background: Human metapneumovirus (HMPV) is an important aetiologic agent of respiratory tract infection (RTI). This study aimed to describe the prevalence, genetic diversity, and evolutionary dynamics of HMPV.
Methods: Laboratory-confirmed HMPV were characterised based on partial-coding G gene sequences with MEGA.v6.0. WGS was performed with Illumina, and evolutionary analyses with Datamonkey and Nextstrain.
Results: HMPV prevalence was 2.5%, peaking in February-April and with an alternation in the predominance of HMPV-A and -B until the emergence of SARS-CoV-2, not circulating until summer and autumn-winter 2021, with a higher prevalence and with the almost only circulation of A2c _111dup . G and SH proteins were the most variable, and 70% of F protein was under negative selection. Mutation rate of HMPV genome was 6.95 × 10 ^-4 substitutions/site/year.
Conclusion: HMPV showed a significant morbidity until the emergence of SARS-CoV-2 pandemic in 2020, not circulating again until summer and autumn 2021, with a higher prevalence and with almost the only circulation of A2c _111dup , probably due to a more efficient immune evasion mechanism. The F protein showed a very conserved nature, supporting the need for steric shielding. The tMRCA showed a recent emergence of the A2c variants carrying duplications, supporting the importance of virological surveillance.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)