While it pales in comparison to the winter 2016-17 avian epizootic, Europe has reported low levels of HPAI H5N6 and H5N8 activity in 2018 with most of the H5N6 activity found in Northern & Western Europe, while H5N8 has made appearances in Southern and Eastern Europe, along with Western Russia.
As we've discussed previously, a major bird flu season is generally followed by one or more less severe years (see chart below), and so this relative lull in activity is not unprecedented.
Today the UK's DEFRA has released their 4th assessment of 2018, which covers not only the UK and EU countries, but also recent HPAI H5 reports from Western Russia as well.
Due to its length, I've only included some excerpts. Follow the link to read the report in its entirety. When you return, I'll have a postscript.
Department for Environment, Food and Rural Affairs
Animal & Plant Health Agency
Advice Services Team - International Disease Monitoring
Situation Assessment #4
9 th July 2018
Ref: VITT/1200 Avian Influenza in Europe
This is an update to our previous assessment on the 4 th April 2018 on the current situation for highly pathogenic avian influenza virus (HPAIV) H5N6 in the UK, including the current status of the prevention zones and other findings in Europe and an assessment of the ongoing H5N8 HPAIV outbreaks in poultry in south-eastern Europe and in western Russia.
The two H5N6 outbreaks in poultry in northern Europe in the early part of this year were swiftly controlled with no secondary spread. It is important to note that to date, there have still been no detections of H5N6 HPAI in poultry in the UK, either in the commercial or non-commercial sectors.
There has been one further wild bird finding in the UK (Northern Ireland) and the late winter period to March resulted in sporadic detections of H5N6 in Northern Europe but at much lower levels than with H5N8 in 2017/18. The number of wild bird H5N6 cases, however, has markedly decreased through April into May, probably due to a combination of firstly the departure from the UK of the wintering water birds (which were the main source of virus) and secondly an increased rate of decay of any excreted virus present in the aquatic environment due to higher ambient temperatures, thus diminishing further exposure to resident wild birds.
The risk of further incursions in wild birds in the UK is now considered greatly diminished (reduced to LOW across UK) compared to earlier in the year (Defra, 2018) and as a result the Avian Influenza Prevention Zones in place in England and in Wales were lifted on Friday 25 May 2018.
This report is to inform readers of the ongoing likelihood of more HPAIV findings in wild birds in the UK during the summer and to review the biosecurity needs to continue to prevent incursions into poultry farms and backyard poultry
H5N6 HPAI in Europe
The return migration of wild waterfowl species from their wintering sites in Western Europe (including the UK) to their summer breeding grounds in the Arctic tundra in late March/early April may have been responsible for many of the cases of H5N6 reported in wild birds in northern Europe including Scandinavia since the previous report.
Indeed the general increased movement of waterfowl species across the region leads to further spread of risk. It is interesting to note that the cases were located along the migration route on the Baltic Sea through to Finland (see map below). Going west to east, Demark, Sweden and Finland reported cases in wild birds in April and into May.
Denmark in particular recorded a number of cases in wild birds with 10 findings during April. The species were Eurasian buzzards and a few White-tailed eagles (Haliaeetus albicilla) but also Hooded crows (Corvus cornix), Mute swans (Cygnus olor) and other waterbird species. Sweden reported three more White-tailed eagles in April/early May. Finland reported two cases in White-tailed eagle in mid and late April in south-west near a key migration route. Germany recorded a single case in early May in a Eurasian buzzard, following a nearby case in a White stork (Ciconia ciconia) at the end of April. The White
stork case is interesting in that it may have been a newly arrived spring migrant from Africa and was presumably infected on arrival in Germany.
H5N8 HPAI in Europe
The HPAIV H5N8 strain has only been reported in southern and south-east Europe this year. Bulgaria had not reported any H5N8 cases in poultry since early March until an outbreak on a commercial duck farm in the Drobrich region on the 25 May following an increase in mortality. According to information from the Bulgarian authorities, this premises also had H5N8 HPAI outbreak earlier in October 2017.
The same or very similar virus appears to have been maintained at low level in this area raising the issue of the effectiveness of secondary cleansing and disinfection and/or the need for continual biosecurity preventing incursion from wild birds. Another outbreak of H5N8 has also been recently reported in July in Bulgaria in the same region at a commercial premises.
H5N8 HPAI in western Russia
Since early June, some 32 outbreaks of H5N8 have been reported in commercial poultry across several oblasts of western Russia including Kurskaya Samarskaya, Orlovskaya, Saratovskaya, Kurskaya, Smolenskaya and Penzenskaya. In addition, one outbreak occurred in a large poultry farm of 190,000 birds in Penzenskaya oblast in mid-June.
This emphasises the requirement for robust control measures in order to ensure mitigation for risk of spread of infection. These outbreaks currently present very low risk to UK, because 3migratory wild waterbirds are not migrating from this region until the autumn. The status of H5N8 in wild birds in western Russia is not known at present.
The EU/OIE/FAO international reference laboratory/UK national laboratory at Weybridge has the necessary ongoing diagnostic capability for these strains of virus, whether low or highly pathogenic AI.
The wild migratory waterfowl which have over-wintered in the UK have now returned to their breeding grounds in north-eastern Europe, Russia and the Arctic tundra. The new migration season for overwintering waterfowl arriving in the UK will begin again towards the end of the summer but this may be weather dependent.
We would like to remind readers that while H5N6 and H5N8 HPAI viruses were both circulating in Europe this year, there was a single case of H5N2 HPAI in Russia in December 2017 which could be circulating in wild birds as well.
(Continue . . . )
Interestingly, DEFRA is identifying the recent Russian activity as due to HPAI H5N8, while the OIE continues to only report HPAI H5.
While considered the most likely culprit, the arrival of HPAI H5N6 in Europe last winter, along with the unexpected announcement of an HPAI H5N2 outbreak in Russia last December, has complicated matters.While the threat of avian flu outbreaks has temporarily declined - at least in Western Europe - migratory birds will begin to return to the UK and the rest of Europe from their high latitude summer retreat in a couple of short months.
A study, published in 2016 (see Sci Repts.: Southward Autumn Migration Of Waterfowl Facilitates Transmission Of HPAI H5N1), suggests that waterfowl can pick up new HPAI viruses in the spring (likely from poultry or terrestrial birds) on their way to their summer breeding spots.
Assuming these viruses are biologically `fit' (and can persist in the avian population for the summer - they may reassort with other avian flu viruses - and then be carried south by migratory birds the following fall.Which means, in two or three months, this welcomed lull in European bird flu activity could change. Or not.
The only thing predictable about influenza is, that it is unpredictable.