Increased immunity in previously affected wild birds may reduce the spread of avian influenza

The latest report from the European Food Safety Authority shows that although transmission is still widespread, the total number of highly pathogenic avian influenza viruses detected in poultry has been significantly lower than in previous years.

Image: European Food Safety Authority

According to the latest report, between December 2, 2023 and March 15, 2024, highly pathogenic avian influenza (HPAI) A( H5) approved by the European Food Safety Authority (EFSA). Although transmission remains widespread, the total number of highly pathogenic avian influenza viruses detected in birds has dropped significantly compared with previous years. This decrease has been attributed to, among other reasons, possible immunity in previously affected wild bird populations, thereby reducing environmental contamination, and changes in the prevalent A(H5N1) genotype.

Most highly pathogenic avian influenza outbreaks reported in poultry are initial outbreaks following introduction of the virus by wild birds. Outside Europe, most poultry outbreaks remain concentrated in North America. Of particular concern, however, is the spread of A(H5) to less exposed wild bird populations on the Antarctic continent.

Regarding mammals, the presence of A(H5N5) was reported for the first time in Europe. Furthermore, baby goats in the United States represent the first natural infection with A(H5N1) in ruminants.

Since the last report, as of March 12, 2024, five cases of human infection with avian influenza A (H5N1) have been reported, including one death. Three of the infections were caused by clade 2.3.2.1c viruses and were reported in Cambodia. For its part, China has reported two cases of human infection with avian influenza A (H5N6), including one fatality, as well as four cases of human infection with avian influenza A (H9N2) and one fatal case of co-infection with seasonal influenza A (H3N2). ) and avian influenza A (H10N5). This latest case is the first documented human infection with avian influenza A (H10N5). Despite these cases, human infection with avian influenza remains rare, and sustained human-to-human transmission has not been observed.

For the general EU/EEA population, the risk of infection with clade 2.3.4.4b H5 avian influenza viruses circulating in Europe remains low. However, the risk of infection remains low to moderate for those with occupational or other exposure to infected animals.