A bird flu strain that claimed the life of a schoolgirl in Cambodia has evolved to better infect human cells, in a worrying sign.
Scientists on the ground who made the discovery said the finding ‘needs to be treated with the utmost concern’.
They added that there were ‘some indications’ the virus had already ‘gone through’ a human and picked up the new mutations before infecting the girl.
The 11-year-old girl, from Prey Veng province, last week became the first victim of H5N1 in 2023. Her father has also tested positive for the virus but has not developed symptoms.
Dr Erik Karlsson, who led the team at the Pasteur Institute of Cambodia that decoded the genetic sequence of the girl’s virus, warned that it differed from that taken from birds.
He told Sky News: ‘There are some indications that this virus has gone through a human.
‘Any time these viruses get into a new host they’ll have certain changes that allow them to replicate a little bit better or potentially bind to the cells in our respiratory tract a little bit better.’
But he added that the virus was yet to fully adapt to humans, saying it was fundamentally ‘still a bird virus’.
He said the mutations were unlikely to have occurred in the girl, but probably existed in a ‘cloud’ of viruses with random genetic changes inside birds.
The H5N1 strain — which has a human mortality rate of around 50 percent — has caused record numbers of deaths among wild birds and domestic poultry over the past 18 months.
But the cases in Cambodia have raised concerns that the virus is adapting to infect humans.
The pathogen has already jumped from birds to mammals, sparking fears that it is now one step close to spreading in humans — a hurdle that has so far stopped it from triggering a pandemic.
Genetic testing on the virus was carried out in just 24 hours, scientists said.
It revealed that the girl had caught the 2.3.2.1c strain of H5N1, which is endemic to wild birds and poultry in Cambodia.
This differs from the 2.3.4.4b type that has spread rapidly around the world and infected many birds and mammals, but Dr Karlsson said this was no reason to downplay the threat.
He added: ‘This was zoonotic spillover [of a virus infecting a new species] and needs to be treated with the utmost concern.’
Calling on the world to keep monitoring the virus, he said: ‘Something may be happening here in Cambodia and something may be happening on the other side of the world in South America, but we don’t really know what could cause the problem tomorrow.’
Health authorities in Cambodia say there is no evidence that the virus is spreading between people yet.
But Or Vandine, the country’s health secretary, added that the possibility cannot be ruled out on Monday. She said that we should ‘wait’ for the conclusions of experts probing the cases.
The 11-year-old girl in Cambodia had her infection begin as a fever, cough and sore throat six days before her death.
She was taken to a children’s hospital in Phnom Penh, the capital — around 100km (62miles) away.
Her father also tested positive for the virus — but had no symptoms — and has since tested negative.
It is possible that the 49-year-old, from Prey Veng province, had also handled infected birds.
That is how his young daughter, who has not been named, is thought to have gotten ill.
She was Cambodia’s first human case since 2014.
None of the 29 others who were swabbed for the highly pathogenic virus were infected, results showed.
Yesterday the Centers for Disease Control and Prevention (CDC) said it was ramping up its pandemic preparedness in response to the threat.
The agency said it was in a ‘posture of readiness’ with several vaccine and drug candidates in the works.
National testing capacity was also being built-up in case the H5N1 strain spills over into people.
The World Health Organization (WHO) has described the situation in Cambodia as ‘worrying’ in a noticeable shift in rhetoric.
