Sunday, March 26, 2023

FAO Update: Global Avian Influenza Viruses with Zoonotic Potential (March 2023)


Although the map above suggests that HPAI avian flu activity is concentrated primarily in the United States, Western Europe, the west coast of South America, and in Japan and Southeast Asia - while large swaths of Africa, Russia, China, and the Middle and Far East are free of the virus - the reality is many countries simply do not publicly report outbreaks.  

Australia is one of the few blank spots on the map that we can feel confident is free of the virus, although they are on heightened alert for its potential arrival via migratory birds. 

Countries are essentially on the `honor' system to report outbreaks in poultry, wild birds, mammals, and even humans. There is currently little that international organizations like the FAO, WOAH, and WHO can do to ensure compliance.   

Complicating matters, only HPAI H5 and H7 viruses are considered `reportable', even though other subtypes can pose a risk to human health.  As a result, outbreaks of LPAI H9N2LPAI H3N8, or LPAI H10N3 often go unreported. 

Over the weekend the FAO posted their monthly summary of global avian flu (with zoonotic potential) activity. Due to its length I've only posted some excerpts, so follow the link to read it in its entirety.  I'll have a brief postscript after the break. 

Global Avian Influenza Viruses with Zoonotic Potential situation update

23 March 2023, 17:00 hours; Rome

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 and H11 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 (23 February 2023): in total, 897 outbreaks have been reported in four geographic regions caused by HPAI unknown subtype (14), H5 HPAI (118), H5N1 HPAI (763) and H5N5 (2) (see Table 1 for details).

LPAI events in animals officially reported since last update (23 February 2023): 1 new event was reported (see Table 2 for details).

Number of human cases officially reported since last update (23 February 2023): 7 new events.

Table 3. Epidemiological overview for avian influenza viruses with zoonotic potential


H5N1 HPAI (1997)

- The ‘classic bird flu’, a high pathogenicity AI virus that can occasionally infect humans
- Endemic in several countries in Africa, Americas, Europe, and Asia
- Different clade reassortments including and clades
- October 2020: one influenza A(H5N1) case in Lao People's Democratic Republic in a one-year old female that was exposed to backyard poultry.
- February 2023: Two A(H5N1) human cases were reported in Cambodia caused by clade viruses in an 11 year old female (died) and her father (mild illness) with exposure to poultry [link]

H5N1 HPAI (2020-onwards)

- These H5N1 viruses were first detected in Europe in October 2020 after reassortment of H5N8 viruses with wild bird lineage N1 viruses.
- Since Autumn 2021 there has been domination of the H5N1 clade viruses with a relatively stable genotype
- These viruses have spread globally with the movement of wild migratory birds and have reassorted with local low pathogenic viruses in many places.
- In Africa these viruses were first detected in early 2021.
- In late 2021 they were introduced into Asia
- In late 2021 introduction into the Americas.
- In 2022 Extensive infection in coastal seabirds and mass die offs of numerous ecologically important species of wild bird.
- In mid 2022 the virus was first detected in Central America and late 2022 in South America in wild birds and poultry with the southwards migration of wild birds.
- In many areas these viruses have been maintained in poultry populations and there have been re introductions with wild bird movement.
- There have been a number of mammalian infections reported particularly in scavenging species
- For the updated list of bird species affected by H5Nx HPAI see  HERE.
- For an updated list of mammalian species infected with H5Nx (all clades) see HERE at bottom of the page.
- For an updated list of confirmed human cases with A(H5N1) see HERE.

H5N6 HPAI (2014)
- To date, 83 human cases of influenza A(H5N6) have been reported, 82 occurring in China and one in Lao People's Democratic Republic.
- H5N6 (2017, Netherlands) was not zoonotic and genetically different.
- Detection of a H5N6 HPAI virus in June 2019 in Nigeria marked the first ever report of this subtype on the African continent.
- Outbreaks in wild birds in Western China, in domestic poultry in Viet Nam, and a new introduction reported by the Philippines in the first quarter of 2020
- Reassortants of these viruses with clade H5 viruses has lead to the emergence of a different H5N6 which has largely replaced the clade H5N6 viruses

          (Continue . . . )

Even as global pandemic threats increase, our visibility of what is happening around the globe continues to dim (see  Flying Blind In The Viral Storm).  We often hear about human infections with avian flu, or MERS-CoV, weeks or even months after the fact.  

Assuming we hear about them at all. 

Invariably, this information vacuum is filled by rumors, speculation - and sometimes - even intentional misinformation.  Last week the internet echo chamber was abuzz with (unconfirmed, and likely false) reports of an H5N1 cluster in Ukraine. 

Most reputable media outlets either ignored the report, or dismissed it as highly dubious. But a week later - undeterred by a lack of corroboration - it is still being repeated on social media. 

All of which makes it incredibly difficult to know how close - or far - we really are from seeing HPAI H5N1 evolve into a genuine public health threat. 

Stay tuned, and Caveat Lector