Avian Flu Diary: FAO Global AIV with Zoonotic Potential

#16.539

A decade ago, the list of avian influenza viruses with `zoonotic potential' was pretty short; primarily consisting of H5N1, H7N2, H7N7 and H9N2. Of those, only H5N1 - which had emerged in Southeast Asia in the mid-1990s and then moved westward into Europe and the Middle East - had shown real potential

By 2013, H5N1 appeared on the decline, but it was suddenly joined by a serious contender; H7N9 - which would spark 5 significant waves of human infection in China before it was brought under control in 2017 using a new H5+H7 poultry vaccine.

Over 2013-2014, we also saw the emergence of H10N8 in China, H5N8 in South Korea (which spread globally in 2015 and has reassorted into various H5Nx subtypes), H6N1 in Taiwan, along with a short list of other H7Nx viruses (H7N2, H7N4, etc.).

As the map above illustrates, Europe, Western Africa, and parts of Eastern Asia (South Korea, Japan, Taiwan) have reported the bulk of outbreaks (in poultry, and wild birds) since October 2021. Of note, North America has reported its first outbreaks of HPAI H5 since 2016.

Meanwhile, other regions - including Mainland China, large swaths of Asia and Africa, and the Middle East - are likely under reporting outbreaks.

Despite reporting no outbreaks in poultry in more than a year, China has reported 3 dozen human infections with H5N6 over the past 12 months (see map below), most supposedly via close contact with infected poultry.

This is currently the most active, and deadliest, avian flu affecting humans reported worldwide. So far, H5N6 has not shown an ability to transmit readily from human-to-human.

But, as we saw in PLoS Path: H9N2 Virus-derived M1 Protein Promotes H5N6 Virus Release in Mammalian Cells these HPAI H5 viruses continue to evolve, making them a genuine concern.

A few excerpts from the FAO's latest report. Follow the link for the extensive data provided.

Global AIV with Zoonotic Potential situation update

26 January 2022, 17:00 hours; Rome

The next issue will be distributed on 23 February 2022.

Overview

Situation: This update covers avian influenza viruses with zoonotic potential occurring worldwide, i.e. H5Nx, H7Nx highly pathogenic avian influenza (HPAI) viruses and H5Nx, H6N1, H7Nx, H9N2, H10N7, H10N8 low pathogenic avian influenza (LPAI).

Specific information is available for Chinese-origin H7N9 viruses and HPAI viruses in sub-Saharan Africa in related FAO Avian Influenza situation updates.

HPAI outbreaks in animals officially reported since last update (23 December 2021): in total, 1 050 outbreaks have been reported in four geographic regions (Africa, Americas, Asia, and Europe) caused by H5 HPAI (14), H5N1 HPAI (998), H5N2 HPAI (13), H5N3 HPAI (1), H5N5 HPAI (1), and H5N8 HPAI (23) (see Table 1 for details).

LPAI events in animals officially reported since last update (23 December 2021): 2 new events were reported (see Table 2 for details).

Number of human cases officially reported since last update (23 December 2021): 13 new events were reported in China (12) and in the United Kingdom (1). In China, seven influenza A(H5N6) human infections were reported in Guangdong Province (2), Guangxi Autonomous Region (1), and Sichuan (3) and Zhejiang (1) provinces, with latest onset date on 06 January 2022, and five influenza A(H9N2) human infections were reported in Anhui (1), Hubei (2), and Jiangsu (1) provinces, and in Guangxi Autonomous Region (1). In addition, the United Kingdom reported an A(H5) human infection on 5 January 2022, the case was asymptomatic and exposed to live ducks [reference1; reference2; reference3].

As the above chart illustrates, HPAI H5N1 is the most reported subtype, and Europe is reporting the vast majority of the outbreaks. That said, what is going on in many parts isn't known.

Since 2016 we've seen increasing avian mortality and increased host range in HPAI H5Nx viruses circulating in Europe, including serious infection of several mammalian species (see CDC EID Journal: Encephalitis and Death in Wild Mammals at An Animal Rehab Center From HPAI H5N8 - UK).

Just over a month ago, in ECDC/EFSA Raise Zoonotic Risk Potential Of Avian H5Nx, we looked at growing concerns over the continued evolution of these H5 clade 2.3.4.4b viruses, and their potential to jump species to humans.

While these European H5 viruses haven't shown the same pathogenicity in humans as their Asia cousins, they do bear watching. For more on the spread and evolution of these viruses, you may wish to revisit: