Monday, April 16, 2018

ESA Epidemiological Update: Global Circulation Of Avian Flu

From ESA Report













 #13,272


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 - followed by a slow decline starting in 2009 - to a resurgence in 2015 propelled by the emergence and global spread of HPAI H5 Clade 2.3.4.4.
Along the way we've also seen the emergence and spread of H7N9, H10N8, and others. 
While highly variable, it does appear that big bird flu years (2006, 2008, 2015, and 2017) are often followed by one or more years of lower AI activity.

As discussed previously, between 2010 and 2013, avian flu seemed to be on a downward trajectory, but the emergence of 4 new subtypes in 2013 (H5N8, H7N9, H5N6, H10N8) quickly revived the threat. 
Today France's ESA (Epidemiosurveillance Santé Animale) has published (in French) an overview of  the global avian flu situation.  I've posted some translated excerpts from a larger report below. 
You'll want to follow the link to read it in its entirety, and I'll return with a postscript.
Results of the epidemiological situation of avian influenza worldwide

Submitted by Alizé MERCIER on 16. April 2018 - 12:06.
For the VSI (in alphabetical order)  : Anne Bronner (EB), Didier Calavas (Anses), Julien Cauchard (Anses), Alize Mercier (CIRAD)
for ONCFS: Anne Van De Wiele
Corresponding author: alize.mercier@cirad. en
Source: OIE status Report on avian influenza (February 28 2018) (http://www.oie.int/fileadmin/Home/eng/Animal_Health_in_the_World/docs/pdf/OIE_AI_situation_report/OIE_SituationReport_AI_February2018.pdf)


The epidemiology of avian influenza (AI) is complex. Viruses are constantly evolving and the behavior of each new subtype (and each strain within a subtype), the risks they represent, and control measures in place vary from country to the other.

Since 2005, the epidemiology of AI was characterized by two panzooties. The first wave panzootique began in 2004, with a peak in 2006 followed by a decrease in viral activity until 2012. A second wave is underway since 2013, with a peak observed in 2015.

Since 2013, all regions of the world have been affected by highly pathogenic avian influenza (HPAI) with 68 countries and territories affected. The most affected areas are Europe and Asia. Several African countries are affected, and HPAI circulates in the North American continent while being almost absent in Central America and South America. Over this period, twelve different subtypes of AI were identified. 


The most important viral diversity was reported in Europe (7 subtypes), followed by Asia and the Americas (6 subtypes each), Africa (3 subtype) and Oceania ( 1 subtype). The subtypes H5N1, H5N2 and H5N8 were the most widespread geographically identified in four of the five regions.

Table 1. Regional distribution of subtypes of HPAI detected in domestic birds from January 2013 to January 2018 (source: OIE)





current global situation (February 28)


the last five years, the situation of HPAI is considered outstanding for at least three reasons:

  • the large number of countries and territories affected by HPAI in the bird breeding,
  • the high number of reported outbreaks over this period (commercial farms or backyard) and
  • the large diversity of subtypes circulating, which complicates the control and eradication of the disease.
(SNIP)
 CONCLUSION
The winter season in the northern hemisphere is usually associated with an increased risk of IA. In 2017-2018, there were numerous emergence and re-emergence of H5N8 and H5N6 virus in Asia, Europe and the Middle East. As indicated in the new homes within farms Iraq, Japan, Korea Republic and Saudi Arabia, the geographical scope of these subtypes continues to increase.

Despite the existence of seasonal trends, the risk remains present throughout the year because these viruses are prepared to sustainably among bird populations.
        PDF 2018-04-05_Note-IA-world-report-OIE.pdf


While the decline in avian flu in places like China, North America, and Asia over the past year is pretty obvious, some regions of the world - particularly in the Middle East - don't always report outbreaks to the OIE.  
Which means - while decidedly down compared to 2016-17 and 2014-15 - the actual number of outbreaks around the world this past year is almost certainly greater than the chart at the top of this blog implies. 
None of this tells us what to expect next fall, of course. We've seen one-year lulls and multi-year lulls. But given the number of subtypes in circulation, and avian flu's expansion into the Southern Hemisphere, it doesn't appear that we'll be rid of the threat anytime soon.

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