Bird flu has ‘mutated’ and may spread easier among humans via coughing after two severe cases detected
H5N1 bird flu from an extreme case in the US has mutated to attach to human upper airway cells, health chiefs have warned.
The case, spotted this month in a hospitalised Louisiana man, is the first “severe” bird flu case in the US amid its rapid spread through cows this year.
In nearby Canada, a healthy teenage boy was admitted to intensive care after contracting the same strain in October.
The new US case, like the one in Canada, is believed to have caught the virus directly from birds in his backyard, not through infected cattle.
Tests show both cases involve a mutated version of H5N1 that helps it bind to human upper respiratory cells.
This could make it easier to spread between people through coughing or sneezing, raising concerns the virus is adapting to infect humans more effectively.
Bird flu viruses do not typically bind to a cell receptor in human upper airways, which helps explain why H5N1 rarely infects people or spreads between them.
The mutation was not found in the poultry samples collected on the US patient’s home, “suggesting the changes emerged in the patient after infection,” the US Centre for Disease Control said in a statement published on Thursday.
That was likely true for the Canadian patient too, but officials couldn’t confirm it since they never found the source of the teen’s infection.
Angela Rasmussen, a virologist specialising in emerging infectious diseases, said the news would have been worse if the mutations were found in the virus from Louisiana poultry.
Still, she called the H5N1 situation “grim,” citing a rise in human cases.
“More [genetic] sequences from humans is a trend we need to reverse – we need fewer humans infected, period,” Angela, of the University of Saskatchewan, in Canada, said on X (formerly Twitter).
“We don’t know what combination of mutations would lead to a pandemic H5N1 virus, and there’s only so much we can predict from these sequence data.
“But the more humans are infected, the more chances a pandemic virus will emerge.”
‘I’m becoming concerned’
Dr Peter Hotez, a top virologist from Baylor College of Medicine’s National School of Tropical Medicine in the US said the development shows how quickly the bird flu situation is “evolving”.
“I was hoping H5N1 wouldn’t continue to accelerate,” he also wrote on X.
“But it looks like the force of infection, rate at which susceptible individuals become infected, cattle, poultry, is pretty high.
“Given the ability of this virus to mutate, or reassort with seasonal flu, I’m becoming concerned”.
Reassortment is the merging of genetic material between seasonal flu and animal flu-like H5N1, and is more likely in winter, as flu cases surge.
At least 65 human H5N1 cases have been confirmed in the US.
This year, linked to an outbreak in dairy cows first reported in March.
About 60 per cent caught the virus from infected cows.
Most others were exposed to infected poultry, either during bird culling or, in Louisiana’s case, through a backyard flock.
Two cases had no known source.
The World Health Organisation (WHO) says the human risk remains low, but urges countries to share information quickly for monitoring and preparedness as the virus spreads.
‘Just one mutation away’
Experts fear the bug, which has infected at least 904 people and killed 465 across the world since 2003, could mutate to spread from human to human, triggering another pandemic.
This week, an animal sanctuary in Shelton, Washington, announced that twenty exotic cats, including a Bengal tiger, four cougars, a lynx and four bobcats, have died after contracting bird flu.
This increase in transmission gives the virus lots of opportunities to mutate – a process where a pathogen changes and can become more dangerous.
Recently, scientists discovered H5N1 is just one mutation away from developing the ability to transmit person-person.
In a bid to bolster the country’s defences, the UK Health Security Agency (UKHSA) has secured H5 jabs to be rolled out in the event of any such outbreak.
Last month, the Department for Environment, Food and Rural Affairs confirmed cases of H5 bird flu at a poultry farm in Yorkshire, England.
The department said all poultry would be humanely killed and a protection zone set up to cover 3km around the site.
However, it has not yet been detected in humans in the UK.
The British government recently announced that it had procured five million doses of an H5 vaccine, in case the virus does indeed start to spread between humans.
Bird flu: Could it be the next human pandemic?
By Isabel Shaw, Health Reporter
The H5N1 bird flu is running rampant in wildlife around the world and is now spreading in cows.
In recent months, it infected people in Canada and the US leaving them severely unwell.
This increase in transmission has given the virus lots of opportunities to mutate – a process where a pathogen changes and can become more dangerous.
Scientists fear it’s only a matter of time before one of these mutations makes it better at spreading among mammals – and potentially humans.
Experts recently discovered H5N1 is already just one mutation away from developing the ability to transmit person-person.
Some experts believe the virus could already be spreading among some animal species.
So far, there is no evidence that H5N1 can spread between humans.
But in the hundreds of cases where humans have been infected through contact with animals over the past 20 years, the mortality rate is high.
From 2003 to 2024, 889 cases and 463 deaths caused by H5N1 have been reported worldwide from 23 countries, according to the World Health Organisation.
This puts the case fatality rate at 52 per cent.
Leading scientists have already warned an influenza is the pathogen most likely to trigger a new pandemic in the near future.
The prospect of a flu pandemic is alarming.
Although scientists have pointed out that vaccines against many strains, including H5N1, have already been developed, others are still in the pipeline.