H5N1 bird flu reaches Australia, killing thousands of birds in about 690 events

H5N1 avian influenza was detected in Australia in mid-June in migratory seabirds, which likely carried it from the Antarctic to Australian islands and then inland, Mongabay reported. Amandine Gamble, who studies pathogens in endangered seabirds at Cornell University in the United States, said in a statement that the outbreaks mark the loss of the last continent previously free from the virus. She said there are serious concerns for wildlife in Australia, New Zealand and surrounding islands, which are home to many already vulnerable endemic species, meaning animals found nowhere else.

The virus has spread rapidly since then, killing thousands of birds in about 690 "events" as of 6 October, according to Mongabay. The outlet reported that an event may involve a confirmed infection or death of one animal, or of many. It reported that H5N1 has also infected mammals, including endangered Australian sea lions (Neophoca cinerea) at key breeding sites.

Mongabay reported, citing the Food and Agriculture Organization of the United Nations, that as of the article's publication the virus had infected about 613 types of bird and about 112 mammal species, both wild and domestic. Christine Johnson, director of the National Science Foundation Center for Pandemic Insights at the University of California, Davis, said the virus has moved aggressively into many species and into what she called different ecological niches.

According to the World Organisation for Animal Health, those at greatest risk include seabirds such as terns, gannets and albatrosses, other waterbirds including ducks, grebes and swans, and pinnipeds such as seals and sea lions. Bird and mammal species that survive by hunting or scavenging are also at risk, according to the organisation. Mongabay reported that scientists and government officials are increasing surveillance of what it described as the largest-ever avian flu "panzootic," meaning a wildlife pandemic. The outlet reported that few mitigations are available: removing carcasses and, for a handful of species, vaccination.

A mild form of avian flu circulates among wild birds, much like the common cold in humans, and migratory species, especially waterfowl, are the natural hosts, according to Mongabay. The outlet reported that when wild birds encounter domestic poultry, avian flu can mutate and turn deadly, becoming Highly Pathogenic Avian Influenza (HPAI), and that this happened with H5N1. It stated that the first description of an infection that killed large numbers of poultry dates to 1878 in northern Italy, then called "fowl plague," and that in 1955 German animal virologist Werner Schäfer determined it was an influenza virus. An HPAI H5 strain was found on a chicken farm in Scotland in 1959, according to the article.