Friday, June 29, 2018

ECDC: Avian Influenza Overview, February – May 2018


Because LPAI and HPAI avian flu reports come in from all over the globe, often belatedly or with varying levels of detail, it isn't always easy to maintain an accurate sense of bird flu's progress and evolution.  
While `breaking news' is important, so is looking back, and analyzing what has transpired over the past few months.  And you'd be hard pressed to find any entity that does surveillance reviews better than the ECDC. 
Today we have a quarterly review - covering the time period from mid-February to mid-May 2018 - which looks not only at the avian flu situation in Europe, but also around the globe.
This 50-page PDF (which I've already saved to my desktop for future reference), is chock full of charts, graphs, maps, and analysis.
Below you'll find  the Executive Summary, and a couple of snippets from the report, but you'll want to download the full report ( Avian influenza overview, February – May 2018 - EN - [PDF-2.31 MB]), and read it in its entirety.  

Executive summary

Between 16 February and 15 May 2018, three highly pathogenic avian influenza (HPAI) A(H5N6) and 11 HPAI A(H5N8) outbreaks in poultry holdings, one HPAI A(H5N6) and one HPAI A(H5N8) outbreak in captive birds, and 55 HPAI A(H5N6) wild bird events were reported in Europe. There is no evidence to date that HPAI A(H5N6) viruses circulating in Europe are associated with clades infecting humans. 

Fewer HPAI wild bird cases have been detected than during the same period of previous year. Most of mortality events among wild birds involved single birds and species listed in the revised list of target species for passive surveillance. Raptor species constitute 74% of the HPAI-infected wild birds found dead. Those raptor species probably became infected by hunting or scavenging HPAI virus-positive birds, and so raptor cases may predominate later in the course of an HPAI epidemic. 
Despite the important HPAI virus incursion via wild birds there have been few associated HPAI A(H5N6) outbreaks in poultry. Fifteen low pathogenic avian influenza (LPAI) outbreaks were reported in three Member States. The risk of zoonotic transmission to the general public in Europe is considered to be very low. 

The situation in Africa and the Middle East should be closely monitored with regards to HPAI A(H5N1) and A(H5N8). Uncontrolled spread of the virus and subsequent further genetic evolution in regions geographically connected to Europe may increase uncertainty and the risk for further dissemination of virus. 

Long-distance migrating wild birds from southern Africa, e.g. the common tern ( Sterna hirundo ), may be included in targeted active surveillance schemes at a few priority locations in Europe in order to detect HPAI A(H5)-infected migrating birds early. However, the risk of HPAI introduction from non-EU countries via migratory wild birds to Europe is still considered to be much lower for wild birds crossing the southern borders than for those crossing the north-eastern borders.

  • The risk of zoonotic transmission of avian influenza (AI) viruses to the general public in the EU/EEA countries is considered to be very low.
  • HPAI A(H5N6) wild bird cases were detected from east to west Europe, as far as Ireland, through the north European regions, suggesting that there were multiple primary introductions of HPAIV into the EU via migrating wild birds.
  • Fewer HPAI wild bird cases have been detected this year than during the same reporting period in 2017. Even if there is uncertainty around conclusive reasons to explain this observed difference, it may be the result of a lower AI virus prevalence in wild birds, a smaller susceptible wild bird population (due to an existing population immunity given the antigenic similarity of HPAIV A(H5N8) circulating in 2017 to HPAIV A(H5N6) in 2018) or a later onset of winter.
  • As seen in previous years, raptors probably become infected with HPAIV by hunting or scavenging HPAIV-positive birds, and so raptor cases may predominate later in the course of an HPAIV epidemic.
  • In this reporting period, the high proportion of raptor and scavenger cases reported may be biased by the heterogeneous implementation of the passive surveillance across years and Member States (e.g. increased proportion of raptor and scavenger species tested compared with previous years; the cut-off value for wild bird mortality events applied to test birds found dead for AI, differing by Member States and wild bird species within Member States).
  • Relative to the number of wild bird events there have been few associated HPAI outbreaks in poultry.

While the slowdown in avian flu reports this past winter in Europe, the Middle East, and China are quite welcome - particularly after the record setting 2016-2017 bird flu season - the history has been that very active `bird flu years' are often followed by one or more less active seasons.
ESA Epidemiological Update: Global Circulation Of Avian Flu

The above chart shows outbreaks of avian flu reported to the OIE from 2005 to the start of 2018, and highlights the initial surge associated with the emergence of HPAI H5N1 early in the last decade and its sudden westward expansion to Europe, Africa and the Middle East - followed by a slow decline starting in 2009 - to a resurgence in 2015 propelled by the emergence and global spread of HPAI H5 Clade
Joining H5Nx, we've also seen the emergence and spread of LPAI and HPAI H7N9, H10N8, and an array of lesser LPAI and HPAI viruses. 
Since we've seen one-year lulls and multi-year lulls, we don't know how long this latest respite will last. 
But considering the growing number of novel subtypes in circulation, HPAI's recent expansion into the Southern Hemisphere, and reports of fresh HPAI H5 activity in Russia, we need to be using this lull to learn as much as we can about the current avian flu threats, and to prepare for whatever comes next.
Because, whether it's a change in a virus we know - like H5Nx, or H7N9, or something new or unexpected coming out of left field - something always seems to come next.

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