The claim appears in a Facebook video dated July 30, featuring a woman saying bird flu “does nothing to humans”.

“Even if a million human beings on earth had bird flu, they wouldn’t even be doing this,” she said in the video, before mimicking a cough (timestamp one minute 11 seconds).

“The World Health Organization (WHO) should be telling you that bird flu is of no threat to human beings."

Bird flu, also called avian influenza, primarily affects poultry and wild birds, although it has infected some mammal species.

Five virus subtypes have infected humans, according to the US Centers for Disease Control and Prevention (CDC).

The World Health Organization has reported that subtypes H5N1 and H7N9 caused most human infections in the Western Pacific.

Most human cases involved the latter strain between 2013 and 2019, the WHO reported.

Scientists were particularly concerned about a variant of the H5N1 variant named clade 2.3.4.4b that's rapidly spread among poultry and other animals, University of Queensland professor Paul Griffin wrote in The Conversation.

Humans can be infected through contact with live or dead infected animals, the CDC reported.

Symptoms include coughing, fatigue and fever, but it was often deadly, the CDC reported.

The WHO recorded 889 human cases of H5N1 bird flu from January 1, 2003, to May 3, 2024.

Those cases resulted in 463 deaths; a case fatality rate of 52 per cent.

Dr Scott Roberts, an infectious disease specialist at Yale Medicine, said H5N1 posed a low overall threat to the public because the odds of getting infected were small and humans were not transmitting the virus to other humans.

But Dr Roberts said for half the people infected, the health impacts were severe.

“There have been roughly 900 known human cases, of which approximately 50 per cent have been fatal,” he told AAP FactCheck.

“So this infection that kills approximately one out of every two infected people hardly ‘does nothing’ to humans as she states.”

British virologist Professor Wendy Barclay, head of Imperial College London’s Department of Infectious Disease, said while infected people have died, others experienced only mild symptoms.

She said some young dairy farm workers in the US who contracted bird flu had suffered only conjunctivitis or mild respiratory symptoms.

But she said the claim that it wasn’t a threat to humans was incorrect.

“Bird flu does kill people much more so than normal seasonal flu… the highly pathogenic viruses have got this extra ability to spread outside of your lungs and go all over your body.”

Prof Barclay said the 52 per cent case fatality rate could be an overestimate because some mild or asymptomatic infections may not be noticed.

“If one million people got infected… I don't think 500,000 of them will die, but it would be a significant number,” she said.

“And I think what's alarming is that the people who have died have actually tended to be quite young and otherwise healthy, which is a different pattern than we see with seasonal flu, where it's the elderly who really suffer.”

The WHO recorded Australia’s first human case of H5N1 in May 2024 in a two-year-old girl who had recently visited India.