Risk of bird flu spread in humans is ‘enormous concern’, says WHO

The World Health Organisation’s chief scientist has said the risk of bird flu spreading to humans is of ‘enormous concern’.

Since 2020, an outbreak of H5N1 bird flu has led to the deaths of tens of millions of poultry and more recently spread of the virus has been seen within mammals, including cattle in the US.

Earlier this month it was reported that a person in Texas was recovering from bird flu after being exposed to the virus through dairy cows – the first reported case of mammal to human transmission. It was the second case in the country after a poultry worker was infected in 2022, officials said.

Speaking at an event in Geneva to announce new measures to tackle airborne diseases, WHO chief scientist Dr Jeremy Farrar said that the avian influenza virus has had an ‘extremely high’ mortality rate among the humans infected to date.

But there has been no record of human-to-human transmission as yet.

‘H5N1 is (an) influenza infection, predominantly started in poultry and ducks and has spread effectively over the course of the last one or two years to become a global zoonotic – animal – pandemic,’ he said. 

‘The great concern, of course, is that in doing so and infecting ducks and chickens – but now increasingly mammals – that that virus now evolves and develops the ability to infect humans. And then critically, the ability to go from human-to-human transmission.’

He went on to urge further close monitoring and investigation by public health authorities of the outbreak among dairy cattle in the US and what was causing the spread.

We have to make sure, he added that if there was human-to-human transmission, ‘we were in a position to immediately respond with access equitably to vaccines, therapeutics and diagnostics.’

Dr Farrar was speaking as WHO announced updated language around airborne pathogens after Covid-19 highlighted a lack of commonly agreed terms among medics and scientists.

The UN health agency will now refer to ‘infectious respiratory particles’ or IRPs, which instead of aerosols and droplets, to avoid any confusion about the size of the particles involved, he explained.

But when asked about the potential public health risk of H5N1, he warned cautioned that vaccine development was not ‘where we need to be’.