The bird flu virus isolated from a girl who died of bird flu has mutated to make it better suited to human cells, Sky News has been told.
The 11-year-old girl is thought to have been infected by her family’s poultry In Prey Veng province, in the south Cambodia.
Her father also tested positive for the H5N1 virus but was asymptomatic.
Dr Erik Karlsson, who led the team that decoded the genetic sequence of the girl’s virus at the Institut Pasteur in Cambodia, said it was different from samples taken from birds.
“There are some indications that this virus has infected humans,” he revealed in an exclusive interview.
“Every time these viruses enter a new host, they undergo certain changes that allow them to replicate better or perhaps bind better to the cells in our airways.”
The mutation is unlikely to occur in girls, but could exist in a “viral cloud” of random genetic changes in birds, he said.
“One or two viruses in the cloud are better able to survive and become dominant populations just by entering a new host,” he said.
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But Dr Carlson added that the virus has not yet fully adapted to humans. “It’s still an avian virus,” he said.
The genetic material of the virus was sequenced in just 24 hours using technology developed by the British company Oxford Nanopore.
It suggests that the virus is the 126.96.36.199c variant of H5N1, which is circulating in wild and domestic birds in Cambodia, and not the 188.8.131.52b strain, which spread rapidly around the world and started infecting some mammals.
But Dr Carlson said it would be wrong to downplay the threat of the Cambodian variant.
“This is a zoonotic spillover [of a virus infecting a new species] And it needs to be given the utmost attention,” he warned.
According to the World Health Organization (WHO), there have been 873 human cases of H5N1, including 458 deaths.
But so far, there is no evidence that the virus spreads easily from person to person.
A key reason is that the bird flu virus latches on to receptors found only in cells deep in the human lung.
Widespread transmission requires a mutation that enables it to bind to receptors on cells in our nasal passages, as human influenza viruses do.
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These cells are more susceptible to airborne viruses, but release a cloud of infectious material with each breath.
But Dr Carlson said changes in the virus must be carefully monitored around the world.
“Something could happen here in Cambodia, something could happen on the other side of the world in South America, but we really don’t know what problems it will cause tomorrow,” he said.
“It’s critical that we work together to tackle all of these problems at the same time. We’d love to get rid of zoonotic diseases, but it’s still a major problem.”
In January 2022, the UK Health Security Agency reported a case of human infection with avian influenza, although the person was asymptomatic.
So far this winter, more than 3,100 people have been exposed to the H5N1 virus through close contact with sick birds. None of them tested positive.
Health officials are also analyzing a small number of samples taken from patients with flu symptoms to check whether the bird flu virus is spreading unknowingly.
Dr Carlson said: “It is concerning that it has gone global so quickly.
“In Europe and North and South America, there have been large-scale infections of poultry and spread to mammals.
“Each of these spillover effects is a problem.”