The virus, which likely originated in Denmark, was first detected in Brittany in 2020. It quickly spread across mainland France and replaced several previously circulating strains. Scientists from the Ploufragan-Plouzané-Niort Laboratory of the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) launched an in-depth study to understand this rapid shift.
“We noticed this new genotype because it coincided with a rise in outbreaks and more severe cases of flu in pigs — high fever, respiratory distress, coughing, and even abortions in sows,” said Gaëlle Simon, Head of the Pig Immunology and Virology Unit at ANSES.
Genetic and antigenic analyses of samples collected between January 2019 and December 2022 confirmed that the H1N2#E virus was markedly different from strains previously circulating in France. These differences allowed the virus to escape the immunity developed through past infections or vaccinations.
Comparative analysis with other known swine influenza viruses indicated that H1N2#E most likely came from Denmark and was introduced to France through imports of infected animals, either directly or via other European countries.
ANSES scientists also raised concerns about the potential for interspecies transmission. Since 2020, the H1N2#E virus has caused several outbreaks on turkey farms and was linked to a serious human case of swine flu in 2021. As pigs are susceptible to both human and avian flu viruses, they can serve as "mixing vessels" for the development of new hybrid strains. The last flu pandemic in 2009 was caused by a swine-origin influenza virus.
The emergence of H1N2#E highlights the urgent need for strict biosecurity measures on pig farms, ANSES emphasized. This includes quarantining newly arrived animals and close monitoring for symptoms of swine flu. The agency also pointed out that, as of now, reporting cases of swine influenza in France is not mandatory — a gap that experts suggest should be addressed.
pigprogress.net