Since October 2021, Europe has been experiencing the most severe outbreak of highly pathogenic avian influenza (HPAI) ever recorded, caused by H5Nx viruses (almost exclusively H5N1) of clade 2.3.4.4b. Furthermore, since the fall, a new pattern of spread of the highly pathogenic avian influenza (HPAI) virus has been observed in migratory wildlife (particularly greylag geese and barnacle geese) as well as in poultry farms and captive bird facilities.

In France, following a lull of several months in poultry farms, several outbreaks in farms have been detected since late November 2023, leading the Ministry of Agriculture and Food Sovereignty to raise the epizootic risk level for HPAI to its highest level, thereby enabling the strengthening of preventive measures to protect poultry farms. In this context, and given the current situation in Europe and France, a so-called “active” surveillance program for avian influenza cases among individuals exposed to an HPAI outbreak is being tested in four regions to enable early detection of any animal-to-human transmission. This situation calls for heightened vigilance among individuals exposed to these viruses as well as among various stakeholders in animal and human health.

What is avian influenza?

Avian influenza is an animal disease caused by influenza viruses that affect a wide variety of bird species. These diseases can sometimes be transmitted to other species, including humans and many species of wild or domestic mammals. However, transmission of these viruses to humans remains rare, and none of the avian influenza viruses currently known are capable of sustaining human-to-human transmission.

• Learn more about avian influenza

What is the purpose of monitoring human cases of avian influenza?

For several years, Santé publique France has been conducting surveillance of human cases of zoonotic influenza. This surveillance is based on monitoring clinically suspected cases of avian or swine influenza (so-called “passive” surveillance) reported by healthcare professionals. Its objective is to:

• detect as early as possible any symptomatic case of avian or swine influenza in humans in order to promptly initiate appropriate medical care and investigations aimed at reducing the risk of transmission to others (isolation of confirmed cases and investigation of contacts and co-exposed individuals);

• describe and characterize human cases of infection with an avian or swine influenza virus.

Preventing the Risk of Avian Influenza Transmission to Humans

In terms of prevention, Santé publique France, in collaboration with several partners (DGS, DGAL, ANSES, Mutuelle Sociale Agricole, and the French Office for Biodiversity), has also developed an informational brochure on avian and swine influenza, explaining how these viruses are transmitted, how to avoid infection, and what to do in case of exposure to risk, particularly if symptoms appear. The brochure is available for download and can be ordered.

Preventing the risk of avian influenza viruses spreading to humans relies on wearing personal protective equipment when handling sick or dead birds (impermeable gloves, protective goggles, FFP2 masks), as well as on all biosecurity measures when an outbreak occurs (see the Ministry of Agriculture’s leaflet).

Given the current circulation of human, avian, and swine influenza viruses within the country, it is important to emphasize the importance of seasonal flu vaccination for professionals exposed to avian and swine viruses in order to limit the risk of reassortment between human and animal influenza viruses.