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Based on events monitored over the past weeks, FAO expects increased activity of H5Nx subtype highly pathogenic avian influenza (HPAI) in birds
across Europe, Asia, the Middle East and potentially Africa during the autumn and winter of 2021-22. Strains of H5 HPAI virus are being detected in migratory birds in Western Europe, with most recent cases reported in Denmark, Germany, and the United Kingdom
of Great Britain and Northern Ireland. The risk of disease introduction into other countries along wild bird migratory flyways is regarded as high. The Netherlands have already issued an order to keep poultry indoors following an outbreak of HPAI on a farm
and Italy has reported an outbreak in domestic turkeys. These reports are the latest in a sequence of detections in wild birds and poultry over the past weeks and months, starting with a notification in the South-Eastern Russian Federation mid-September, followed
by observed westwards movement of virus. Farms in countries that are situated along migratory flyways should put in place enhanced measures for prevention, early detection and diagnosis of H5 HPAI, and for outbreak response. As other strains of avian influenza
virus are also present in wild birds and poultry, co-circulation of multiple avian influenza strains provides opportunity for reassortment, potentially creating novel strains that could be more infectious or more virulent. The HA gene of the viruses from these
recent outbreaks falls within H5 Clade 2.3.4.4b (reference).
Similar viruses have also been introduced into China via wild birds in late 2020 (reference1,
reference2).
In this context it is noteworthy that a
trend of increased human cases infected with clade 2.3.4.4b H5N6 viruses,
associated with severe disease, has been reported from China.
The zoonotic potential of avian influenza viruses should therefore be considered and appropriate personal protection measures applied when dealing with suspect cases in wild birds or outbreaks in poultry – or unexplained mortality in either.
CONTEXT
Starting with a notification of H5N1 HPAI in wild birds (mute swans –
Cygnus olor) in the South-Eastern Russian Federation mid-September, strains of H5Nx HPAI virus have been detected in migratory birds in several European countries (Denmark, Estonia, Finland, Germany, Latvia, Serbia, Sweden, the United Kingdom), with
the most recent cases reported on 16 October in Denmark, affecting a teal (Anas sp.), and in Germany, affecting a Eurasian wigeon (Anas penelope), and on 26 October at a wild bird rescue centre in the United Kingdom. This month, the Netherlands
have already issued an order to keep poultry indoors following an outbreak of HPAI on a farm and Italy has reported an outbreak in domestic turkeys. In the Middle East, Israel reported an outbreak of H5N1 HPAI in domestic poultry on 16 October 2021. In Europe,
it appears that H5Nx HPAI viruses persisted through the summer in wild birds, posing a continuous risk of spillover into domestic bird populations. This situation has been complicated by the introduction and spread of novel, but related, virus strains via
wild birds migrating to Europe during the autumn (EFSA).
The recent rapid and extensive geographic distribution of H5Nx HPAI viruses, the species affected and timing of outbreaks indicate introduction
and spread through migratory wild birds. Once introduced, onwards spread between farms is high risk due to movement of infected poultry, contaminated boots, clothing, vehicles, and farm equipment, and via poultry faeces/litter. These H5Nx HPAI viruses continue
to show good adaptation to domestic and wild birds, and have already demonstrated pathogenicity in various species, including mammals.
August to October is the period when migratory birds leave their spring-summer breeding sites in Russian Federation in search of feeding grounds
in warmer locations, stopping over at multiple resting sites in Europe and Western Asia. Certain migratory bird species also extend their range to southern latitudes, as far as sub-Saharan Africa. So far no infections in wild birds with these viruses has been
reported in East, West or Southeast Asia, however events in 2020 suggest that re-introduction of a novel strain of clade 2.3.4.4b H5Nx virus is a possibility.
Information shared via the Global Initiative on Sharing All Influenza Data (GISAID)
and the OIE/FAO global network of expertise on animal influenzas (OFFLU)
indicate that the H5Nx viruses currently circulating mostly fall within H5 Clade 2.3.4.4b. H5N6 clade 2.3.4.4b viruses have been detected in the majority of the viruses
sequenced from human infections reported from China, mainly in the second half of 2021, as well as human cases detected in Nigeria earlier in 2021 and human cases detected in the Russian Federation in late 2020 (reference1,
reference2,
reference3,
reference4).
Precautions should therefore be taken to reduce human exposure to these potentially zoonotic viruses. FAO reminds countries about the importance to share full genome sequences and virus isolates with the scientific community
early for further analysis and research so that epidemiological links between outbreaks can be established, virus evolution monitored and the zoonotic potential of emerging viruses assessed. This information is also used to match the appropriate vaccines
to currently circulating strains, and novel viruses.
There is a possibility that antigens in existing inactivated vaccines, used in several countries to protect poultry, may not be well matched to these novel, currently circulating strains. This is under review by FAO/OIE Reference Laboratories.
FAO ADVISES COUNTRIES AT RISK TO:
- Increase surveillance efforts in areas identified to be at higher risk of HPAI introduction through wild birds by immediately
testing sick or dead poultry as well as dead/hunted wild birds for the presence of HPAI viruses
- Limit direct and indirect contact between domestic poultry, including ducks, and wild birds (e.g. keep poultry indoors, use fences
or nets to reduce contact between domestic poultry and wild birds); pay particular attention to sources of poultry drinking water to ensure it cannot be contaminated or it is treated appropriately before use
- Raise awareness among poultry keepers, the general population, traders, marketers, hunters, and any other relevant stakeholder
about HPAI, precautionary and personal protection measures as well as reporting and collection mechanisms for sick or dead birds
- Ensure implementation of biosecurity measures along the value chain, including farms, live bird markets, slaughter points, etc.
to limit further spread of the disease
- Ensure laboratories have capabilities for diagnosis of the circulating H5Nx HPAI
- Provide mechanisms for reporting sick or dead birds (hotlines, collection points) and raise awareness about the importance of
reporting
- On infected farms, conduct appropriate cleaning and disinfection and take action on carcasses, slurry and faecal waste to ensure
they do not pose a risk for further transmission and spread of virus
- Upon detection of outbreaks timely alert neighbouring countries as well as international organizations, including the World Organisation
for Animal Health (OIE)
- Share full genome sequences, studies on antigenic characterization and virus isolates with the scientific community for further
analysis and research; or send specimen for full genome sequencing to an international Reference Laboratory - for the benefit of all countries at risk
- Initiate/reactivate a compensation policy and allocate financial resources; ensure compensation for poultry culled as part of
control measures during an HPAI outbreak is provided in a timely manner, see Good Emergency Management Practice pp. 18-19:
http://www.fao.org/3/a-ba0137e.pdf
- If vaccines are being used to prevent avian influenza, assess antigenic characteristics of any new viruses detected using antisera
from vaccinated birds; ensure antigenic assessments are done on any H5 HPAI viruses detected in well vaccinated, clinically affected flocks and, where necessary, update vaccine virus. It is important to recognize the possibility of breakthrough infections
in vaccinated flocks from these strains, especially those in which immunity is not uniform or levels of antibody are low.
- Action against wild birds, particularly indiscriminate hunting or destruction of habitat, should not be undertaken
WHAT FAO IS DOING:
- Monitor and assess the evolving disease situation. To share updates on your country situation, please do not hesitate to contact
FAO at [log in to unmask]
- Liaise with FAO/OIE Reference Laboratories and partner organizations to assess virus characteristics and provide laboratory protocols
for detection
- Raise awareness about important epidemiological and virological findings and their implications
- Provide recommendations for affected countries and those at risk addressing preparedness, prevention and disease control
- Provide support for risk assessment and mapping to identify hot spots for risk mitigation and the implementation of risk-based
surveillance
- Offer support in provision of diagnostic reagents and personal protective equipment, provided certain conditions are met (contact:
[log in to unmask])
- Offer assistance to national authorities for shipment of samples as well as virus sub-typing and sequencing, provided certain
conditions are met (contact: [log in to unmask])
To contact FAO for further information or support please write to Keith Sumption, FAO Chief Veterinary Officer at
[log in to unmask].
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