Australia Awaits Test Results On 1st Suspected H5N1 Detection (wild bird)

Virology Down Under

#19,210

I awoke this morning (4am EDT) to find an overnight message from Ian McKay - author of Virology Down Under - on the first suspected case of H5N1 in Australia. Details are scant, but you can read Ian's blog post (and hopefully peruse some of his other posts while you are there).

It was only yesterday we looked at a preprint on H5N1 threatening Australia's Heard Island Elephant Seal population, and over the past few years we've looked at a number of reports (see here, here, and here) on Australia's all-but-inevitable fate. 

Remarkably, 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.

It has long been believed that that this good fortune is due in part 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. 

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.

But in 2023 HPAI was detected in the the Antarctic region - providing the virus with a potential southerly approach - raising fears that Oceania's luck with H5 may be on borrowed time (see Australia : Biodiversity Council Webinar on HPAI H5 Avian Flu Threat).

While today's suspected case has not been confirmed, and a single incursion is hardly an invasion, today's report reminds us how tenuous Oceania's HPAI H5N1-free status genuinely is. 

Of particular concern, when HPAI H5N1 conquers new territories it typically reassorts with a variety of local LPAI viruses, sometimes generating unique genotypes.  

Oceania may provide the virus with unique opportunities to improve to evolve, or to adapt to new hosts. 

Hopefully we'll get further clarification from Australia in the hours and days ahead.