WildLife Group of the SAVA
Situation Assessment
Several recent papers have looked at the evolution of the 2.3.4.4 clade of H5 viruses and have concluded that migratory birds play an important role not just in the long range dissemination of the viruses but also in terms of their evolution . Continuous genetic mixing of HPAI viruses in wild birds including with LPAI viruses is resulting in increased genetic diversity at whole genome level . Furthermore , the contact between wild birds and poultry in many environments ( direct or indirect ) leads to virus transmission in both directions , with further opportunity for virus evolution via genetic re-assortment once within poultry , particularly at live bird markets . The rapid evolution of the viruses may manifest in a change in infection kinetics affecting pathogenicity , transmission and host range , an increased affinity for human cells or the evolution of new clades . It highlights the importance of maintaining strong surveillance programmes as well as sharing data on virus sequences and summary disease statistics in a timely manner ( He et al ., 2017 ; Takemae et al ., 2017 ).
From the European perspective , not only is it clear that H5N8 HPAI has continued to persist in the environment and potentially in indigenous populations of wild birds at local level over the summer in some regions so therefore is likely to continue to cause risk of disease incursions into poultry farms with insufficient biosecurity but it is also clear there are other threats to consider . Wild bird migration season is starting which will bring birds from their breeding grounds in Central and North Eurasia to Europe for wintering . Any extreme cold weather in the coming months will drive those birds inland and further west . Last year , the first cases of H5N8 HPAI were observed in the middle of October to early November . The potential for new incursions to Europe of H5N8 with these wild bird populations are real .
This year , the cases in wild birds and poultry are already occurring . It is also important to note the pattern of H5N8 HPAI emergence in 2014 when the virus was observed in Japan and South Korea in wild birds and a few months later it was detected in Europe and North America . If the same pattern of wild bird transmission occurs this year , we might expect to see expansion in the range of H5N6 HPAI potentially to similar areas , as it was reported in high numbers of migratory wild birds in Japan over the summer together with waves of infection in poultry in the Republic of Korea . This virus has some affinity for human cells unlike H5N8 HPAI virus , therefore public health issues will also need to be considered carefully .
Conclusion
The overall risk level for the UK is still at present considered to be “ LOW ”, which is our normal yearround background risk level , given avian influenza viruses are usually circulating at a low level in wild waterfowl . Therefore , the risk for poultry also remains “ LOW ” for introduction of infection onto individual premises , but will depend on levels of biosecurity . This level is likely to increase in the next month or so , and as it can also be driven by changing weather conditions , which we will also be monitoring closely in collaboration with the Met Office . We strongly recommend that all poultry keepers ( including backyard keepers ) review their biosecurity measures and business continuity plans now , as the risk level may well increase in the coming weeks . They should familiarise themselves with government guidance on good biosecurity and how to report suspicion of disease appropriately .
Further information is available here : https :// www . gov . uk / guidance / avian-influenza-bird-flu including updated biosecurity advice for poultry keepers for England
References
FAO ( 2017 ) Transboundary threats to food and nutrition security in Southern Africa . http :// www . fao . org / 3 / a-i7691e . pdf
He , G . et al . ( 2017 ) Identification of two novel avian influenza a ( H5N6 ) viruses in wild birds , Shanghai , in 2016 . Veterinary Microbiology 208 : 53-57 .
Takemae , N . et al . ( 2017 ) Five distinct reassortants of H5N6 highly pathogenic avian influenza A viruses affected Japan during the winter of 2016-2017 . Virology 512 : 8-20 .
This publication is available at https :// www . gov . uk / government / collections / animal-diseases-internationalmonitoring Any enquiries regarding this publication should be sent to us at iadm @ apha . gsi . gov . uk
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