Identifying the viral and epidemiological factors behind the apparent global extinction of influenza B/Yamagata
- 1University of Georgia
Abstract
Until 2020, two lineages of the influenza B virus had co-circulated globally. Measures to control the COVID-19 pandemic led to a near-absence of influenza infections. While B/Victoria reemerged in late 2021, there have been no reports of B/Yamagata since the pandemic. To investigate which epidemiological and immunological factors were primarily responsible for the extinction of B/Yamagata, we developed a global model for the two influenza B lineages. To mimic the transmission impacts of the pandemic, we implemented a transient reduction in contacts and identified parameter values that recapitulated viral coexistence dynamic before the pandemic and the qualitative post-pandemic outcomes of B/Victoria (reemergence in late 2021) and B/Yamagata (extinction). Our results suggest that, rather than immunological or evolutionary mechanisms, the extinction of B/Yamagata was mainly driven by its lower basic reproduction number making the virus particularly vulnerable during the early phase of the pandemic. Stochastic simulations of our best-fitting model suggest that B/Victoria was also close to extinction during this period. We investigate the model to assess the feasibility of B/Victoria eradication through vaccination and the potential for a sustained re-emergence of B/Yamagata in the 2026-27 flu season, thus highlighting important considerations for biosafety.
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BibTeX
@misc{gutierrez2026identifying,
title = {{Identifying the viral and epidemiological factors behind the apparent global extinction of influenza B/Yamagata}},
author = {M. A. Gutierrez and P. A. Rohani},
howpublished = {medRxiv},
year = {2026},
month = jul,
doi = {10.64898/2026.07.22.26358639},
url = {https://www.medrxiv.org/content/10.64898/2026.07.22.26358639v3},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Identifying the viral and epidemiological factors behind the apparent global extinction of influenza B/Yamagata
AU - M. A. Gutierrez
AU - P. A. Rohani
PY - 2026
DA - 2026/07/22
PB - medRxiv
DO - 10.64898/2026.07.22.26358639
UR - https://www.medrxiv.org/content/10.64898/2026.07.22.26358639v3
AB - Until 2020, two lineages of the influenza B virus had co-circulated globally. Measures to control the COVID-19 pandemic led to a near-absence of influenza infections. While B/Victoria reemerged in late 2021, there have been no reports of B/Yamagata since the pandemic. To investigate which epidemiological and immunological factors were primarily responsible for the extinction of B/Yamagata, we developed a global model for the two influenza B lineages. To mimic the transmission impacts of the pandemic, we implemented a transient reduction in contacts and identified parameter values that recapitulated viral coexistence dynamic before the pandemic and the qualitative post-pandemic outcomes of B/Victoria (reemergence in late 2021) and B/Yamagata (extinction). Our results suggest that, rather than immunological or evolutionary mechanisms, the extinction of B/Yamagata was mainly driven by its lower basic reproduction number making the virus particularly vulnerable during the early phase of the pandemic. Stochastic simulations of our best-fitting model suggest that B/Victoria was also close to extinction during this period. We investigate the model to assess the feasibility of B/Victoria eradication through vaccination and the potential for a sustained re-emergence of B/Yamagata in the 2026-27 flu season, thus highlighting important considerations for biosafety.
ER -