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The ECDC publishes a highly detailed avian influenza surveillance report roughly every 3 months, and while they tend to be EU centric, in its 60+ pages you'll find ample coverage of outbreaks and infections from around the world.
While the HPAI H5N1 clade 2.3.4.4b virus gets most of our attention, primarily due to its rapid spread around the globe, we are also closely watching several other zoonotic influenza viruses including H3N8, H5N6, LPAI H9N2, and H5N1 clade 2.3.2.1c.
The HPAI H5 threat has changed substantially over the past 7 years, starting out with H5N8 in 2016, then transitioning (via reassortment) to H5N6 in 2018, and then finally to H5N1 in 2020. And with these changes in subtype came changes in its behavior.
While H5N1 is the dominant subtype, there dozens of genotypes circulating in Europe, with even more globally. Some of these genotypes are likely more dangerous, or better adapted to mammals, than others.
Over time, the virus has also expanded its host range, both in mammals and wild bird species (see chart below), moving from primarily affecting waterfowl (in blue) to heavily impacting shorebirds (in green).
The report cites:
Mammals
• The ongoing serological survey in all fur farms in Finland resulted in 29 additional serologically positive farms since the beginning of September 2023. Those farms were keeping American mink, red and Arctic foxes, common raccoon dogs and sables. Only a few of those farms reported mortality (3) and clinical signs (2), which indicates possible asymptomatic infection that could go undetected by passive surveillance in those species.
• Unlike the mammalian infections reported in Europe during the summer months, mainly caused by the BB genotype, the recent A(H5N1) viruses identified in wild mammals (Eurasian lynx, Eurasian otter and harbor seals) in Finland and Denmark belonged to the AB genotype.
• In South America, HPAI continued to spread along the east coast and resulted in high mortality of major breeding colonies of South American sea lions and southern elephant seals in Argentina, Brazil and Uruguay. The virus has also been detected in southern elephant seals in the Antarctic region, home to half of their global population. There is also concern for high mortality in other wild mammal populations such as Antarctic fur seals on those islands.
• The high percentage (about 43%) of European viruses collected from mammalian species containing molecular markers of mammalian adaptation in the PB2 protein indicates that these mutations can be rapidly acquired by the virus during infection in mammalian species. Viruses containing such mutations may have a greater zoonotic potential.
• To date, no key mutations associated with the switch in the virus binding preference from avian- to human-type receptors were identified in the A(H5) virus collected from mammalian species in Europe.
These quarterly overviews are a valuable reference source. Click the link below to download the report in its entirety.
Avian influenza overview September– December 2023
European Food Safety Authority, European Centre for Disease Prevention and Control, European Union Reference Laboratory for Avian Influenza, Cornelia Adlhoch, Alice Fusaro, José L Gonzales, Thijs Kuiken, Gražina Mirinavičiūtė, Éric Niqueux, Karl Ståhl, Christoph Staubach, Calogero Terregino, Katriina Willgert, Francesca Baldinelli, Kateryna Chuzhakina, Roxane Delacourt, Alexandros Georganas, Milen Georgiev and Lisa Kohnle
Abstract
Between 2 September and 1 December 2023, highly pathogenic avian influenza (HPAI) A(H5) outbreaks were reported in domestic (88) and wild (175) birds across 23 countries in Europe. Compared to previous years, the increase in the number of HPAI virus detections in waterfowl has been delayed, possibly due to a later start of the autumn migration of several wild bird species.
Common cranes were the most frequently affected species during this reporting period with mortality events being described in several European countries. Most HPAI outbreaks reported in poultry were primary outbreaks following the introduction of the virus by wild birds, with the exception of Hungary, where two clusters involving secondary spread occurred. HPAI viruses identified in Europe belonged to eleven different genotypes, seven of which were new.
With regard to mammals, the serological survey conducted in all fur farms in Finland revealed 29 additional serologically positive farms during this reporting period. Wild mammals continued to be affected mostly in the Americas, from where further spread into wild birds and mammals in the Antarctic region was described for the first time.
Since the last report and as of 1 December 2023, three fatal and one severe human A(H5N1) infection with clade 2.3.2.1c viruses have been reported by Cambodia, and one A(H9N2) infection was reported from China. No human infections related to the avian influenza detections in animals in fur farms in Finland have been reported, and human infections with avian influenza remain a rare event.
The risk of infection with currently circulating avian H5 influenza viruses of clade 2.3.4.4b in Europe remains low for the general population in the EU/EEA. The risk of infection remains low to moderate for occupationally or otherwise exposed people to infected birds or mammals (wild or domesticated); this assessment covers different situations that depend on the level of exposure
- EN - [PDF-2.31 MB]
