Cases of avian influenza declining in Europe

Europe has recorded the lowest number of highly pathogenic avian influenza cases in poultry and wild birds since 2019/2020.

These are the main findings of the latest report on avian influenza by the European Food Safety Authority (EFSA), the European Centre for Disease Prevention and Control (ECDC), and the EU reference laboratory (EURL), based on reported data between 16 March and 14 June 2024. The report further noted that the risk to the general public remains low.

The improvement in the situation regarding the number of cases of avian influenza in Europe could be linked to several factors, which could include flock immunity acquired by certain wild bird species, depletion of some wild bird populations, reduced viral contamination of the environment, changing composition of circulating HPAI virus genotypes, and decreased detection of dead wild birds.

Between 16 March and 14 June 2024, 15 HPAI outbreaks in poultry were reported from 2 countries in Europe: 8 A(H5N1) from Hungary and 7 A(H5Nx) from Bulgaria. This compares to a total of 173 A(H5) outbreaks during the same period in the previous epidemiological year and is the lowest number recorded for this period since 2019.

Of those outbreaks, 11 were reported as primary and 4 as secondary. For 10 of these outbreaks, indirect contact with wild birds was considered the most likely source of introduction, although for both countries the number of HPAI virus detections in wild birds was very limited (1 in Bulgaria and 0 in Hungary). In total, approximately 1 million birds died or were culled in the HPAI-affected poultry establishments.

During the time period from 16 March to 14 June 2024, a total of 24 A(H5N1), 1 A(H5N5) and 2 A(H5Nx) virus detections were reported from Germany (13), Poland (3), the UK (2) and, 1 each from Bulgaria, Denmark, France, Latvia, Moldova, Norway, Romania, Slovenia and Spain. The overall number of HPAI virus detections in wild birds (27) was about 16 times lower than in the previous reporting period (2 December 2023 to 15 March 2024). Of note, HPAI virus detections were only recorded in 3 colony-breeding seabirds: a European herring gull in France (A(H5Nx)), a sandwich tern in Spain (A(H5N1)) and another European herring gull in the UK (A(H5N5)).

Overall, the data suggests that HPAI viruses were only circulating at a low level, if at all, without causing mass mortality events in wild bird populations in Europe during the current reporting period.

Most of the HPAI outbreaks reported in poultry worldwide continued to be concentrated in North America, particularly in the US. In Asia, the HPAI situation in domestic and wild birds intensified during this reporting period.

Apart from previously affected countries such as Japan, Korea and Taiwan, now also India and Iraq officially reported virus detections in domestic and wild birds, respectively. Of specific concern are the HPAI virus detections in wild birds in China due to the upcoming autumn migration to Europe. HPAI viruses are expected to continue to spread in the Antarctic region.

For the first time in many years, Australia has been affected by 3 different HPAI virus subtypes during the current reporting period, which likely represents a separate event from the rest of the world: A(H7N3), A(H7N8) and A(H7N9).

During the current reporting period, the first natural HPAI virus detections were confirmed in the following mammal species: alpaca (US), cattle (US) and walrus (Norway). In Europe, primarily carnivorous or scavenging mammal species (i.e., cat, Eurasian otter, raccoon and red fox) continued to be affected in low numbers.

Outside Europe, all HPAI virus detections in mammals during this reporting period were reported from North America: more than 5 different mammal species, including domestic and peri-domestic mammals in close contact with humans (alpaca, cat, cattle and house mouse). In most of these detections the new A(H5N1) virus genotype B3.13 was identified.

Extensive spread of A(H5N1) virus genotype B3.13 has been observed among more than 130 dairy farms in 12 US states. While within-herd transmission has been characterised to be primarily through milking equipment during the milking process, between-farm spread has likely been due to the movement of animals, people, vehicles, equipment and fomites. Further transmission from cattle to other species categories (i.e., domestic and wild mammals, domestic and wild birds, and humans) has been demonstrated.

Sporadic cases of zoonotic avian influenza A(H5N1), A(H5N6) and A(H9N2) continued to be reported outside Europe during the period March to June 2024. In addition, there was a third human case of avian influenza A(H10N3) virus infection and the first ever laboratory-confirmed human infection with A(H5N2) virus was reported.

Experts have emphasised their recommendation to enhance surveillance of avian influenza in view of the next influenza season.

Tags: Poultry, Hungary, wild birds, outbreaks, highly pathogenic avian influenza, A(H5N1), A(H5Nx), Bulgaria, Europe