FAO Update: Global Avian Influenza Viruses with Zoonotic Potential

#17,045

Although it is always risky to predict what (seasonal/avian/swine/novel) flu will do in the months ahead, the unusual persistence of HPAI H5 avian flu in Europe and North America over the summer - and its spread to many new avian (and occasional mammalian) species - has many experts concerned over what this fall and winter may bring. 

Human infections have thankfully been very few and mild.  Nevertheless, 4 months ago the CDC Added Zoonotic Avian A/H5N1 Clade 2.3.4.4b To their IRAT List of influenza viruses with pandemic potential.

In years past, outbreaks of avian flu - both in Europe and North America - have been sporadic.  This year, Europe has seen the worst outbreak in their history (see the ECDC Avian influenza overview June – September 2022) which recently characterized Europe's outbreak as:

The 2021–2022 highly pathogenic avian influenza (HPAI) epidemic season is the largest HPAI epidemic so far observed in Europe, with a total of 2,467 outbreaks in poultry, 47.7 million birds culled in the affected establishments, 187 outbreaks in captive birds, and 3,573 HPAI virus detections in wild birds with an unprecedent geographical extent reaching from Svalbard islands to South Portugal and Ukraine, affecting 37 European countries.

Meanwhile, in the United States - where HPAI H5 made only its second appearance in 7 years - outbreaks rose sharply and unexpectedly during the month of September. 

There is a very real prospect for Europe to experience their 3rd consecutive year of epizootic HPAI H5 this winter, and North America their 2nd year. 

Global Avian Influenza Viruses wFAO Update: Global Avian Influenza Viruses with Zoonotic Potential 

28 September 2022, 17:00 hours; Rome

Overview
This update covers avian influenza viruses with zoonotic potential occurring worldwide, i.e. H5Nx, H7Nx high pathogenicity avian influenza (HPAI) viruses and H3N8, H5Nx, H6N1, H7Nx, H9N2, H10N3, H10N7, H10N8 low pathogenicity avian influenza (LPAI).

Specific information is available for Avian Influenza A(H7N9) virus viruses and Sub-Saharan Africa HPAI in related FAO Avian Influenza situation updates.

HPAI outbreaks in animals officially reported since last update (24 August 2022): in total, 1 729 outbreaks have been reported in four geographic regions (Africa, Americas, Asia, and Europe) caused by by HPAI (1), H5 HPAI (19), H5N1 HPAI (1 706), H5N2 HPAI (2), and H5N8 HPAI (1) (see Table 1 for details).

LPAI events in animals officially reported since last update (24 August 2022): 0 new events were reported.

Number of human cases officially reported since last update (24 August 2022): 1 new influenza A(H5N6) human case was reported in Guangxi Autonomous Region, China on 14 September 2022. The case involves a 6-year-old girl who had visited a live poultry market and had exposure to poultry from the market before onset of symptom on 30 July 2022 [reference]. In addition, one influenza A(H10N3) human case was reported to WHO, Western Pacific Region [reference].

           (SNIP) 

 

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As the above graphic (Figure 1) illustrates, HPAI H5N1 makes up more than 90% of the detections this year, with Europe and the Americas reporting the vast majority of outbreaks.  Reporting from Asia and Africa, however, are not as robust and it is likely that many outbreaks go unreported.

In addition to its continued circulation in temperate regions over the summer, the assumption is that HPAI H5 has been circulating in the high latitude roosting areas of Alaska, Canada, Siberia, and the arctic over the summer months  - potentially reassorting with other avian flu viruses - and will return this fall on the wings of southbound migratory birds. 

For North America, most concerning is what may be happening in Alaska, since more than 200 species of birds - many of which migrate to the lower 48 each winter -  spend their summers in the 19-million acre Arctic National Wildlife Refuge. 

While we may not know what evolutionary changes (may, or may not) have occurred over the summer, we do know that HPAI has been frequently detected in Alaska over the past few months, as well as above the arctic circle in Europe.  

This recent, rapid global spread of HPAI H5 has a lot of scientists genuinely worried (see Nature Why unprecedented bird flu outbreaks sweeping the world are concerning scientists).

But even if HPAI H5 remains only a threat to poultry and wild birds (and the occasional fox, or seal), it could still have a big impact on the cost of poultry and eggs this winter, and large culling operations could put thousands of farmers (and their employees) into financial jeopardy. 

Where HPAI H5Nx goes from here is unknowable, and while it may eventually fizzle, we can't afford to ignore its potential to evolve into an even more problematic virus.