First UK case of swine flu variant found in humans
A rare strain of swine flu has infected a person in Britain for the first time, health authorities have said.
An individual with mild respiratory symptoms was found to be infected with influenza A(H1N2)v, a virus commonly found in pigs.
The virus is different from the H1N1 flu which caused the 2009 swine flu pandemic that killed more than 400 people in the UK.
Around 50 people globally have previously been found to be infected with this type of swine flu and this is the first time a person has tested positive in the UK.
The genetic sequence of the British case is distinct to the 50 other cases of the H1N2 strain globally but is very similar to the current variants in UK porcine populations.
The individual was mildly unwell and recovered fully, the UK Health Security Agency (UKHSA) said. It is unknown how the patient, thought to be from North Yorkshire, contracted the infection.
The person visited their GP after developing cold-like symptoms and routine lab tests identified the H1N2 strain which is more commonly seen in the farmyard animal.
H1N2 is a common pig pathogen and is known to occasionally jump to humans, but very rarely spreads from person to person. It is unknown if the patient caught the virus directly from an animal, food, a fellow human, or another source.
UKHSA officials are investigating where the person most likely caught the infection and are also tracking down close contacts who may have been exposed.
Prof Paul Hunter, professor of medicine at UEA, said a H1N2 virus “has yet to cause a major outbreak in humans”.
There were seven H1N2 cases globally in 2022, he said, adding that there is no evidence it is more dangerous than any other form of flu.
“Person to person transmission does not appear to be very efficient and sustained person to person transmission has not been reported so far,” he said.
Preliminary analysis found the infection detected in the UK is a new clade, dubbed 1b.1.1, which is genetically different from any other human cases of influenza A(H1N2) in the world.
However, it is very similar to infections known to be circulating in UK pigs.
Occasional spillover infections
Experts have said there are often occasional spillover infections of pig viruses into people and that this is likely an isolated incident with limited potential to spread.
Meera Chand, incident director at UKHSA, said: “It is thanks to routine flu surveillance and genome sequencing that we have been able to detect this virus.
“This is the first time we have detected this virus in humans in the UK, though it is very similar to viruses that have been detected in pigs.
“We are working rapidly to trace close contacts and reduce any potential spread. In accordance with established protocols, investigations are underway to learn how the individual acquired the infection and to assess whether there are any further associated cases.
Christine Middlemiss, chief veterinary officer, said: “We know that some diseases of animals can be transferred to humans – which is why high standards of animal health, welfare and biosecurity are so important.
“Through our animal and human surveillance systems we work together to protect everyone. In this case we are providing specialist veterinary and scientific knowledge to support the UKHSA investigation.
“Pig keepers must also report any suspicion of swine flu in their herds to their local vet immediately.”
Isabel Oliver, a UKHSA chief scientific officer, said the existing flu vaccines were unlikely to work against this pig virus as they are designed for the most common types of flu in people.
