OFFLU Report: Continued Expansion of HPAI H5 in wildlife in South America and Incursion into the Antarctic region

Credit OFFLU 
 

#17,828

It has taken 27 years for HPAI H5 - first detected in a goose in Guangdong Province, China in 1996 - to evolve sufficiently enough to make its way across almost the entire globe (excluding Oceania), arriving last October to the tip of South America and into the Antarctic waters.

During that time the virus has reinvented itself numerous times, forming dozens of new clades and subclades, a diverse array of subtypes (H5N1-H5N9), and scores of genotypes (see J Vet Sci: Evolution, Global Spread, And Pathogenicity Of HPAI H5Nx Clade 2.3.4.4 for an overview).

Some have been far more successful than others - and while many have gone extinct - today's clade 2.3.4.4b is arguably the best international traveler of the bunch. 

Two years ago it crossed both the Atlantic and Pacific oceans (apparently multiple times) setting up housekeeping in North America. A year later it reached South America, and two months ago it appeared in Antarctica.

Four months ago we looked at the the FAO/WOAH OFFLU Network's 14-page cautionary statement on the impacts, and challenges of HPAI facing South America and the strong likelihood that avian flu would soon arrive in the Antarctic region. 

Now that it has happened, today the OFFLU ad-hoc group on HPAI H5 in wildlife of South America and Antarctica has published a 37-page follow-up report that looks at the likely further spread of the virus in the Antarctic and the potential for HPAI H5 to move into Oceania. 

Due to its length I've only reproduced the link and Abstract below.  You'll want to download the read the document in its entirety, but I'll have a postscript after the break. 

Continued expansion of high pathogenicity avian influenza H5 in wildlife in South America and incursion into the Antarctic region

Abstract 

This report summarises the spread and impact of high pathogenicity avian influenza of the subtype H5 (HPAI H5) clade 2.3.4.4b in South America, its incursion into South Georgia, and the risk for further spread in the Antarctic region and for incursion into Oceania. The focus of the report is on HPAI H5 in wildlife, and covers neither spread in poultry nor sporadic spillover to humans, as these are the subjects of other reports. We do fully support a One Health approach to HPAI H5: an integrated, unifying approach that aims to sustainably balance and optimise the health of people, animals (wild and domestic) and ecosystems.

Between the first detection of HPAI H5 virus in South America in October 2022 and November 2023, the deaths of 597,832 birds of at least 82 species and 50,785 mammals of at least 10 species have been reported, with the bulk of the reported mortality occurring in Peru and Chile. The highest numbers of reported mortalities in association with the HPAI H5 outbreak include marine mammal species, such as South American sea lions (Otaria byronia) (~32,000) and southern elephant seals (Mirounga leonina) (~17,000), and seabird species, such as cormorants (Phalacrocoracidae) (~262,000), Peruvian boobies (Sula variegata) (~242,000), Peruvian pelicans (Pelecanus thagus) (~62,000), Humboldt penguins (Spheniscus humboldti) (~4,000), various species of gulls (Larus spp.) (~7,000), terns (Larosterna inca, Sterna hirundinacea and Thalasseus spp.) (~3,500) and frigatebirds (Fregata spp.) (~7,000). These numbers undoubtedly represent only a fraction of the total mortality.

The first incursion of HPAI H5 virus into the Antarctic region was detected in October 2023 in South Georgia (Islas Georgia del Sur), part of the Scotia Arc. At the same time, virus incursion was detected in the Falkland Islands (Islas Malvinas), on the continental shelf of South America. The species found infected or suspected infected with HPAI H5 virus include brown skua (Stercorarius antarcticus), kelp gull (Larus dominicanus), southern fulmar (Fulmarus glacialoides), black-browed albatross (Thalassarche melanophris), grey-headed albatross (Thalassarche chrysostoma) and southern elephant seal, and could be involved in the next stage of spread of HPAI H5 virus in the Antarctic region.

The risk of viral transmission to other islands of the Scotia Arc and the Antarctic Peninsula is considered high, and considered medium to several islands that lie in the southern parts of the Pacific, Atlantic and Indian Oceans. From these locations, HPAI H5 virus is likely to spread further in the Antarctic region; and from there, incursion into Oceania is plausible.

HPAI H5 virus is likely to spread further among Antarctic wildlife, potentially infecting the 48 species of birds and 26 species of marine mammals which inhabit this region. The negative impact of HPAI H5 on Antarctic wildlife could be immense, because their presence in dense colonies of up to thousands of pinnipeds and hundreds of thousands of birds facilitates virus transmission and may result in high mortality. As has been seen in the northern hemisphere, it is possible that HPAI H5 virus will persist in the Antarctic region in coming years and spread variably among its wildlife populations.

Although little can be done to stop virus spread, there are a few options for response available. It is important to continue monitoring and surveillance of wildlife populations for HPAI H5 virus incursion and assessing spread and impact of disease, both to provide information for wildlife managers to adapt conservation plans, and to help policymakers mitigate and prevent future HPAI outbreaks. It is also important to take biosafety measures to reduce the risk of human-mediated spread of HPAI H5 virus to new areas, and to reduce the risk of human infection with HPAI H5 virus.

          (Continue . . . )

With the introduction of HPAI H5 to Antarctica, the only continental region untouched now becomes Australia, New Zealand, New Guinea (aka `Oceania'). Even though H5N1 emerged in Southeast Asia more than 25 years ago, and has been widely reported across much of the Indonesian archipelago for decades, the virus has never managed to get a foothold in Oceania.

This good fortune is often attributed to the Wallace and Weber lines - imaginary dividing lines used to mark the difference between animal species found in Australia and Papua New Guinea and the rest of Southeast Asia (see 2008's Will Wallace’s Line Save Australia from Avian Influenza?).

While separated by a relatively narrow strait, on the western side you'll find Elephants, monkeys, leopards, tigers, and water buffalo while on the eastern side, you'll mostly find marsupials (kangaroos, Koalas, wombats, etc.).  

These stark faunal differences also extend to birds, reptiles, and even insects. 

Importantly for avian flu, very few migratory birds appear to cross the Wallace line (see The Australo-Papuan bird migration system: another consequence of Wallace's Line).

But the arrival of HPAI to the Antarctic potentially provides the virus with a new approach (from the south); assuming it becomes well enough entrenched in the avian colonies that roost there over the summer. 

While that hasn't happened yet, it may become a possibility in the future.  OFFLU states:

Given movement data demonstrating connectivity between the polar front to both the Antarctic and Subantarctic islands of Oceania, and Oceania itself, it is plausible that if HPAI H5 were present in the Antarctic region directly south of Oceania, it could be introduced to Oceania.

Now that summer has arrived in the Southern Hemisphere, the risk of migratory birds carrying the virus to Australia or New Zealand has lessened - at least for the next few months - but will presumably pick up again next April (autumn down under). 

The following November update from Wildlife Health Australia explains the risks of seeing HPAI H5 reach Oceania.  I've only posted  the link and an excerpt from the 11-page PDF report, so follow the link to read it in its entirety.