H5N1 bird flu ‘capable of airborne transmission'

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a day ago

H5N1 bird flu is capable of spreading through the air, a new animal study from the US Centres for Disease Control (CDC) has found.
H5N1 was believed to spread primarily through direct contact with infected animals or their bodily fluids, but the new findings suggest it can also be transmitted through respiratory droplets and aerosol, raising concerns about its ability to cause a future pandemic.
The study, published in Emerging Infectious Diseases, was based on a sample of H5N1 extracted from a dairy worker in Michigan who contracted the virus last year.
The CDC scientists then used this sample to infect a group of ferrets, which are considered a 'gold standard' in flu research due to the similarity between their respiratory system and that of human.
The infected animals were placed in close proximity to six other healthy ferrets and observed for three weeks.
Within 21 days, three of the previously uninfected ferrets had contracted H5N1 – without any direct physical contact – indicating that the virus can travel through the air through a 'respiratory droplet transmission model'.
The researchers also collected aerosol samples from the air surrounding the ferrets, and found infectious virus and viral RNA to be present, indicating that H5N1 can, like Covid-19, be transmitted through both respiratory droplets and aerosols – smaller particles that can travel longer distances and remain suspended in the air for extended periods.
Respiratory droplets, on the other hand, are larger and do not travel as far in the air, requiring closer contact with an infected person for transmission.
Since 2024, at least 70 people in the US have been infected with H5N1, the majority of them workers on poultry or dairy farms where the virus was present. Bird flu has spread to more than 1,000 dairy farms across the country over the past year and is now endemic among US cattle.
'This study is important as it provides yet more evidence that the H5N1 influenza virus that is circulating in dairy cattle in the USA is, in principle, capable of respiratory transmission,' Prof Ed Hutchinson, Professor of Molecular and Cellular Virology, MRC-University of Glasgow Centre for Virus Research told The Telegraph.
'[The study] does this using experimental animals that experience and transmit influenza in similar ways to humans, so it warns us of what the virus could do in humans under the right circumstances,' Prof Hutchinson added.
The study's authors warned that their findings underline the 'ongoing threat to public health' H5N1 poses, emphasising the need for 'continual surveillance and risk assessment… to prepare for the next influenza pandemic'.
Most human cases reported in the US so far have resulted from direct physical contact with sick animals or their fluids, including cow's milk.
But experts have warned that, as H5N1 continues to infect animal populations and 'jump' to humans, it is only a matter of time before the virus undergoes the mutations necessary to spread effectively from person to person.
'Because avian H5N1 viruses cross the species barrier and adapt to dairy cattle, each associated human infection presents further opportunity for mammal adaptation,' the study's authors said.
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