Is influenza B/Yamagata extinct and what public health implications could this have? An updated literature review and comprehensive assessment of global surveillance databases

Abstract

Introduction: Early after the start of the COVID-19 pandemic, a major drop in the number of influenza B/Yamagata detections was observed globally. Given the potential public health implications, particularly with regards to influenza vaccination, we conducted a systematic review of influenza B/Yamagata virus circulation data from multiple complementary sources of information. Methods: We searched articles published until 20th March 2023 in PubMed and EMBASE; examined epidemiological and virological influenza data for 2020-2023 contained in the publicly available WHO-FluNet and GISAID (Global Initiative on Sharing All Influenza Data) global databases, or collected by the multi-national Global Influenza Hospital Surveillance Network (GIHSN) study; and looked for influenza data in the webpages of respiratory viruses surveillance systems from countries worldwide. Results: Highly consistent findings were found across all sources of information, with a progressive decline of influenza B/Yamagata detections from 2020 onwards across all world regions, both in absolute terms (total number of cases), the positivity rate, and as a fraction of influenza B detections. Isolated influenza B/Yamagata cases continue to be sporadically reported, and these are typically vaccine-derived, mistaken data entries or under investigation. Discussion: While it is still too early to conclude that B/Yamagata is (or will soon become) extinct, the current epidemiological and virological data call for a rapid response in terms of influenza prevention practices, particularly regarding the formulation of influenza vaccines. The current epidemiological situation is unprecedented in recent decades, underlying the importance of continuously and carefully monitoring the circulation of influenza viruses (as well as SARS-CoV-2 and the other respiratory viruses) in the coming years.

Disruption of seasonal influenza circulation and evolution during two pandemic events in Southeastern Asia: contrasting the role of human movement and pathogen competition

“…Accordingly, perturbation of influenza virus circulation was more drastic during the COVID-19 pandemic, coinciding with our findings where most internal transmission within Southeastern Asia almost halted. Although we could not study the B/Yamagata lineage in this work, the global disappearance of this lineage from surveillance data since late 2020 attests of the marked perturbation of the COVID-19 pandemic period on influenza dynamics 55 .…”

Integrating dynamical modeling and phylogeographic inference to characterize global influenza circulation

“…Following SARS-CoV-2 emergence in 2020, the global influenza circulation has been substantially altered with potential long-term consequences, 62 as illustrated by the probable extinction of the B Yamagata variant. 63 In such a situation, the long-term and global-scale description of influenza dynamics is more than ever important to identify viral evolutionary pathways for the prediction of vaccine composition, to inform projections on the approaching influenza season in a given region, and, on a more fundamental level, to disentangle the interplay between endogenous and exogenous factors in shaping regional epidemic waves. Phylodynamic approaches may become an invaluable tool to achieve these goals.…”

Passive immunotherapies for the next influenza pandemic

“…In 1977, another global epidemic of H 1 N 1 (virtually unchanged from the 1957 strain 9 ) was initiated, 10,11 resulting in co‐circulation of H 3 N 2 and H 1 N 1 in humans, which has continued to date. Similarly, 2 influenza lineages B (B/Victoria/1987 and B/Yamagata/1988) co‐circulated 12 until recently, 13 leading to deployment of quadrivalent seasonal influenza vaccines.…”