The current epidemiological situation of highly pathogenic avian influenza viruses (avian influenza viruses of the H5N1 subtype of clade 2.3.4.4b in particular) worries the health authorities.
Indeed, these strains are characterized by an extremely rapid diffusion, observed since autumn 2021 in Europe, America, Asia and Africa. The 2021-22 winter season was marked by the largest epizootic ever recorded in Europe. Moreover, these viruses have not ceased to circulate during the summer season, contrary to what has been observed previously, and several outbreaks have been detected in France very recently, both in wild birds and in poultry. or captive birds. Thus, the conditions favorable to a passage to the endemic stage of the disease in wild birds raise fears a new outbreak this winter.
Evidence of crossing the species barrier in wild mammals has increased markedly, with foxes and marine mammals infected with these viruses.
Regarding the passage to humans, 4 people with high exposure to infected poultry had a positive RT-PCR test (one in the United Kingdom in 2021, one in the United States in 2022 and two in Spain in October 2022). These detections were all characterized by no symptoms or very mild symptoms. No human-to-human transmission of this virus has been reported indicating that the virus has not at this stage adapted to the human species.
At the same time, swine influenza viruses are actively circulating in French pig farms (https://plateforme-esa.fr/fr/virus-influenza-porcins). A case of human infection with an influenza virus of porcine origin (H1N2) requiring hospitalization occurred in September 2021 in Brittany, with no evidence of human-to-human transmission.
The DGS therefore calls for increased vigilance with regard to these viruses, specifying the action to be taken in the event of suspicion.
