#16,226
Twice in the last 5 years (fall & winter of 2016-17 and 2020-21) record setting epizootics of H5 avian influenza have swept across Europe, killing uncounted millions of wild birds, and tens of million of farm raised birds. A similarly sized outbreak occurred in the United States & Canada over the winter of 2014-15.
While economically damaging, up until 10 months ago, the viruses causing these outbreaks (European H5Nx) were assumed to pose little or no risk of human infection.
That perception changed last February with the announcement from Russia of the 1st 7 confirmed human infections with H5N8 (see ECDC Threat Assessment Brief On 1st Identified Human Infections With Avian H5N8).
While cases were reportedly mild (or asymptomatic), this shift in zoonotic ability - combined with HPAI H5's continual evolution - has raised fresh public health concerns. A few examples:
Last May, in Science: Emerging H5N8 Avian Influenza Viruses, we looked at a review by two well-respected Chinese scientists (Weifeng Shi and George F. Gao) on the evolution, and growing zoonotic threat, of avian H5N8, stating:
- the ". . . global spread of AIVs, particularly the H5N8 subtype, has become a major concern to poultry farming and wildlife security but, critically, also to global public health."
- And due to the ". . . long-distance migration of wild birds, the innate capacity for reassortment of AIVs, the increased human-type receptor binding capability, and the constant antigenic variation of HPAIVs the authors warned that it was imperative that " . . . the global spread and potential risk of H5N8 AIVs to poultry farming, avian wildlife, and global public health are not ignored."
And while China is thousands of miles removed from Europe, their recent surge in H5N6 human infections is also of concern, as migratory birds could carry this virus south into India, or west into Russia, Europe, or the Middle East.
Yesterday the ECDC, along with the European Food Safety Agency and the European Union Reference Laboratory for Avian Influenza, published a 76-page Scientific Report on avian influenza activity in Europe - and beyond - over the summer.
Avian influenza overview May – September 2021Surveillance report
30 Sep 2021
The 2020–2021 avian influenza epidemic with a total of 3,777 reported highly pathogenic avian influenza (HPAI) detections and approximately 22,900,000 affected poultry birds in 31 European Countries appears to be one of the largest HPAI epidemics that has ever occurred in Europe.
Executive summary
Between 15 May and 15 September 2021, 162 HPAI virus detections were reported in 17 EU/EEA countries and the UK in poultry (51), in wild (91) and captive birds (20). The detections in poultry were mainly reported by Kosovo (20), Poland (17) and Albania (6). HPAI virus was detected during the summer months in resident wild bird populations mainly in northern Europe. The data presented in this report indicates that HPAI virus is still circulating in domestic and wild bird populations in some European countries and that the epidemic is not over yet.Based on these observations, it appears that the persistence of HPAI A(H5) in Europe continues to pose a risk of further virus incursions in domestic bird populations. Furthermore, during summer, HPAI viruses were detected in poultry and several wild bird species in areas in Russia that are linked to key migration areas of wild waterbirds; this is of concern due to the possible introduction and spread of novel virus strains via wild birds migrating to the EU countries during the autumn from the eastern breeding to the overwintering sites.Nineteen different virus genotypes have been identified so far in Europe and Central Asia since July 2020, confirming a high propensity for this virus to undergo reassortment events. Since the last report, 15 human infections due to A(H5N6) HPAI and five human cases due to A(H9N2) low pathogenic avian influenza (LPAI) virus have been reported from China. Some of these cases were caused by a virus with an HA gene closely related to the A(H5) viruses circulating in Europe.The viruses characterised to date retain a preference for avian-type receptors; however, the reports of transmission events of A(H5) viruses to mammals and humans in Russia, as well as the recent A(H5N6) human cases in China may indicate a continuous risk of these viruses adapting to mammals.The risk of infection for the general population in the EU/EEA is assessed as very low, and for occupationally exposed people low, with large uncertainty due to the high diversity of circulating viruses in the bird populations.
Earlier this week, in Czech Republic Reports H5 Bird Flu Outbreak, we looked at a very recent report of an untyped HPAI H5 virus in a small holding in the Příbram region in the Central Bohemian Region. Since then, the Czech Republic State Veterinary Agency has identified the subtype as H5N1.
A new outbreak of bird flu has been confirmed in the Czech Republic after more than four months. It is located in small poultry farming in the village of Trhové Dušníky in the Příbram region in the Central Bohemian Region. The source of the infection is probably wild waterfowl. The breeder reported the death of five geese from his small breed. There were also 16 hens and 11 ducks in it. Clinical signs typical of avian influenza were observed in one of the ducks. The veterinary inspectors immediately started an investigation in the breeding, took preliminary measures and sent the dead pieces to the State Veterinary Institute in Prague for examination. This subsequently confirmed H5N1 bird flu. The breeder did not rule out that the poultry in the breeding came into contact with wild water birds.
It is not immediately clear whether this H5N1 is more closely aligned to the more benign European H5N1, or the more virulent Asian subtype.
But it does remind us that nature's laboratory continues to churn out novel viruses - and while most will be evolutionary failures - it only takes one to plunge us into the next global health crisis.
