A strain of bird flu that claimed the life of a schoolgirl in Cambodia has evolved to better infect human cells, in a worrying sign.
The scientists on the ground who made the discovery said the discovery “must be treated with the utmost concern”.
They added that there were ‘some indications’ that the virus had already ‘passed through’ a human and picked up the new mutations before infecting the girl.
The 11-year-old girl, from Prey Veng province, became the first victim of H5N1 in 2023 last week. Her father also tested positive for the virus but did not develop symptoms.
Dr Erik Karlsson, who led the team from Cambodia’s Pasteur Institute that decoded the genetic sequence of the girl child’s virus, warned that it differed from that taken from birds.
He told Sky News: “There are indications that this virus passed through a human.
“Each time these viruses enter a new host, they undergo certain changes that allow them to replicate a little better or potentially bind a little better to cells in our airways.”
But he added that the virus was not yet fully adapted to humans, saying it was basically “still a bird virus”.
Dr Karlsson said the new mutations were unlikely to occur in the girl, but likely existed in a ‘cloud’ of viruses with random genetic changes inside the birds.
The strain in its current form is unlikely to cause a major outbreak. Large-scale transmission would require a mutation allowing it to bind to a receptor present on the cells of the nose.
CDC says it’s in a ‘readiness position’ for H5N1 in Cambodia
The Centers for Disease Control and Prevention (CDC) said it was in a “preparedness position” with several vaccine and drug candidates in the works.
Genetic testing revealed that the girl had caught the 220.127.116.11c strain of H5N1, which is endemic to wild birds and poultry in Cambodia.
This differs from type 18.104.22.168b which spread rapidly around the world and infected many birds and mammals, but Dr Karlsson said that was no reason to downplay the threat.
He added: “It was a zoonotic overflow [of a virus infecting a new species] and should be treated with the utmost concern.
Calling on the world to continue to monitor the virus, he said: ‘Something can happen here in Cambodia and something can happen on the other side of the world in South America, but we don’t really know what could cause the problem tomorrow.’
H5N1 has a human mortality rate of about 50 percent. There have only been around 870 cases among people worldwide.
The 22.214.171.124b strain has devastated the world’s bird population over the past year.
More than 15 million animals have been culled and killed by the virus itself, while governments have collectively slaughtered more than 200 million worldwide to curb the spread of the virus, including 58 million in the United States alone.
The pathogen has already jumped from birds to mammals, raising fears it is on the verge of spreading to humans – a hurdle that has so far prevented it from triggering a pandemic.
Cambodian health authorities say there is no evidence yet that the virus spreads between people, suggesting the daughter and father caught the virus from the same source – likely an infected bird.
On Monday, Or Vandine, the country’s health secretary, said investigations were still ongoing and while human-to-human spread was unlikely, it could not yet be fully ruled out.
She said we should “wait” for the findings of experts investigating the cases.
Avian flu epidemic: everything you need to know
What is this?
Avian flu is an infectious type of flu that spreads among birds.
In rare cases, it can be transmitted to humans through close contact with an infected dead or living bird.
This includes touching infected birds, their droppings or bedding. People can also catch bird flu if they kill or prepare infected poultry to eat.
Wild birds are carriers, especially by migration.
As they group together to reproduce, the virus spreads rapidly and is then carried to other parts of the globe.
New strains tend to appear first in Asia, from where more than 60 species of shorebirds, wading birds and waterfowl head to Alaska to breed and mingle with migrating birds from the United States. United. Others go west and infect European species.
What strain is currently spreading?
So far, the new virus has been detected in some 80 million birds and poultry worldwide since September 2021, double the record from the previous year.
Not only does the virus spread at high speed, but it also kills at an unprecedented level, leading some experts to say it is the deadliest variant to date.
Millions of chickens and turkeys in the UK have been culled or quarantined, affecting the availability of free-range turkeys and eggs.
Can it infect people?
Yes, but only 860 human cases have been reported to the World Health Organization since 2003.
The risk to people was deemed to be “low”.
But people are strongly urged not to touch sick or dead birds as the virus is deadly, killing 56% of people it manages to infect.
The girl who died in Cambodia saw her infection begin with fever, cough and sore throat six days before her death.
She was taken to a children’s hospital in Phnom Penh, the capital, about 100 km (62 miles) away. She died on February 22.
Her father also tested positive for the virus – but showed no symptoms – and has since tested negative.
It is possible that the 49-year-old man, from Prey Veng province, also handled infected birds.
This is how his young daughter, who has not been named, is said to have fallen ill.
She was the first human case in Cambodia since 2014.
None of the other 29 who were sampled for the highly pathogenic virus were infected, the results showed.
Yesterday the Centers for Disease Control and Prevention (CDC) said it was stepping up its pandemic preparedness in response to the threat.
The agency said it was in a “readiness position” with several vaccine and drug candidates in the pipeline.
National testing capacity was also being boosted in case the H5N1 strain spread among people.
In the UK, health authorities say they have started modeling bird flu pandemic scenarios in response to the threat.
The World Health Organization (WHO) has called the situation in Cambodia “worrying” in a notable shift in rhetoric.
Earlier this month, the agency rated the threat of bird flu to humans as “low.” But the WHO says it may reconsider that status based on the latest update.
Dr Sylvie Briand, director of epidemic and pandemic preparedness and prevention at the WHO, told reporters they were considering the change.
She said: “The global H5N1 situation is concerning given the wide spread of the virus in birds around the world and the increase in reported cases in mammals, including humans.”
Concerns about the transmission of bird flu to humans were raised this month after cases also emerged in mammals, including mink and sea lions.
This brings the virus closer to infection and spread among humans.
Bird flu viruses generally have a harder time spreading among humans because the death rate is so high and the infection can kill so quickly, meaning people die before they have a chance to catch it. convey.
Professor Francois Balloux wrote on Twitter this week that bird flu is a “serious concern”.
But he said that although human-to-human transmission is happening, it is not happening now as it used to, and “by far the most likely scenario for H5N1 is that nothing is happening right now”.
Avian influenza infections in humans are rare.
However, they can occur when enough virus enters the eyes, nose, mouth, or is inhaled.
People in close or prolonged unprotected contact (not wearing respiratory and eye protection) with infected birds or in areas where sick birds, their mucous membranes, saliva or feces have been contaminated may be at greater risk of infection. infection.
But it’s unlikely a human could catch the virus from eating poultry or game birds because the disease is heat-sensitive, meaning meat won’t contain the virus as long as it’s properly cooked. .
An infected bird may appear lethargic, stop eating, have swollen body parts, cough and sneeze. Other birds may die suddenly without any symptoms.
Symptoms in humans are high fever (often over 100 F), cough, sore throat, muscle aches, and general feeling unwell.
Other early symptoms may include abdominal and chest pain and diarrhea.
It can quickly progress to serious respiratory illness, including shortness of breath, difficulty breathing, and pneumonia. People may also suffer from an altered mental state or seizures.