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Bird flu: ‘strong evidence’ suggests the virus first crossed from mammals to humans | Science and technology news

Since 2003, hundreds of people have been infected with the H5N1 virus, but so far they have all contracted it from birds. The current outbreak of bird flu in the United States has infected dairy cow herds in nine states.

By means of Thomas Moore, science correspondent @SkyNewsThomas


Friday May 3, 2024 6:36 PM, UK

Scientists fear bird flu has spread from mammals to humans for the first time, marking a new step in the evolution of the deadly virus.

New analysis concludes there is “strong evidence” that a Texas farmworker tested positive the H5N1 virus caught from sick dairy cattle.

Although other people have been infected with the virus in recent years – including some who have died – they all acquired it from birds.

There is growing concern about the inability of US authorities to contain the spread of the virus.

So far, 36 herds in nine states have tested positive. But testing of milk has suggested the virus has spread much more widely.

The longer it spreads unchecked in a domesticated mammal, the more likely it is to adapt to a new species – and be passed on to people in close contact.

According to the report in The New England Journal of Medicine, the unidentified man’s symptoms were mild. He developed the eye infection conjunctivitis, but had no fever and no difficulty breathing. His lungs were also clear.

He and the people he lived with were given antiviral drugs as a precaution. No one else got sick.

How does bird flu spread?

The team, made up of researchers from the Centers for Disease Control, said: “Since the infected human was a dairy farm worker with reported exposure to sick, suspected infected cows in Texas and with no reported exposure to other mammals or birds, we believe that The genetic and epidemiological data provide strong evidence of human infection following exposure to suspected virus-infected cows.”

Some mammals are infected

The highly pathogenic strain of H5N1 has been spread worldwide by wild birds.

Initially, it was mainly poultry that was infected, and millions were culled to prevent further spread.

But some mammals have been infected, including small numbers of foxes, seals and dolphins in Britain.

There are also suspicions that the virus has spread between farmed mink and within sea lion colonies.

But there was surprise when it turned up in dairy cows in the US, which were suffering from a sharp drop in milk production.

Virus has been spreading for months

There are indications that the virus has spread unnoticed since the beginning of the year. Some cows are asymptomatic.

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Image:
Bird flu has been found in seals in the US and Great Britain. Photo: AP

The scientists believe that the man may have been infected by a virus that enters his eyes through the air in the milking parlour, or because a virus on his hands or gloves is transferred to his eyes.

Although the farm worker only had a mild infection, H5N1 can be serious – and even fatal – to humans.

According to the World Health Organization, 888 people worldwide were infected between 2003 and the end of March this year, with 463 deaths.

Beef and dairy products safe

US authorities have discovered viral fragments – but no active virus – in pasteurized milk. They say dairy products and beef are safe.

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In the United Kingdom, a risk assessment by government scientists has concluded that the threat of a similar outbreak in dairy herds is very low.

They say animals are kept in different conditions and there is little chance of cow flu being carried across the Atlantic Ocean by wild birds.