During the COVID-19 pandemic, world influenza circumstances dropped dramatically due to lockdowns and journey restrictions. However, in areas with fewer restrictions, influenza continued to flow into, fueling its evolution.
Research reveals that world air journey is essential to influenza unfold, and whereas many lineages returned post-pandemic, influenza B/Yamagata could have gone extinct.
During the COVID-19 pandemic, journey restrictions and social measures led to a sharp worldwide lower in seasonal flu circumstances. However, sure influenza strains continued to flow into and evolve in areas with fewer restrictions, notably in tropical areas like South and West Asia. The unfold of seasonal flu is strongly influenced by social behaviors, particularly air journey, and by the periodic emergence of latest strains that evade immunity from earlier infections or vaccinations.
In 2020, nonpharmaceutical interventions (NPIs) aimed toward controlling COVID-19—akin to lockdowns, mandated social distancing, masking, and journey bans—considerably disrupted influenza transmission and evolution. As a end result, world circumstances of seasonal flu, together with A subtypes H1N1 and H3N2 and B subtypes Victoria and Yamagata, noticed a dramatic decline.
In this examine, Zhiyuan Chen and colleagues investigated how these adjustments affected the unfold, distribution, and evolutionary dynamics of seasonal influenza lineages. Using a phylodynamic method, the researchers mixed epidemiological, genetic, and worldwide journey information from earlier than, throughout, and after the COVID-19 pandemic and located that the onset of the pandemic led to a shift within the depth and construction of worldwide influenza transmission.
Although influenza circumstances considerably dropped globally through the pandemic’s peak, in South Asia and West Asia, areas that had comparatively fewer pandemic restrictions, the circulation of influenza A and influenza B/Victoria lineages, respectively, continued. That circulation served as vital evolutionary sources, or “phylogenetic trunk locations,” of influenza viruses through the pandemic interval.
By March 2023, as world air site visitors resumed, the circulation of influenza lineages returned to pre-pandemic ranges, highlighting the virus’ resilience to long-term disruption and its reliance on world air journey patterns to unfold. Notably, nevertheless, the findings additionally present that the influenza B/Yamagata lineage seems to have disappeared for the reason that start of the pandemic, suggesting that the lineage could have since gone extinct.
“The examine by Chen et al. additional reinforces that nonpharmaceutical interventions could be extremely efficient in disrupting viral transmission, pathogen variety, and antigenic evolution, and are arguably more practical than vaccine efforts alone,” write Pejman Rohani and Justin Bahl in a associated Perspective.
Reference: “COVID-19 pandemic interventions reshaped the global dispersal of seasonal influenza viruses” 7 November 2024, Science.
DOI: 10.1126/science.adq3003
