THE UK has recorded its first human case of a new strain of swine flu, the government has announced.
The person tested positive for the bug after visiting their GP in North Yorkshire with breathing problems.
The UK Health Security Agency (UKHSA) is working rapidly to trace contacts and find the source of the infection, with the patient not thought to have had close contact with pigs.
The virus was spotted during routine flu surveillance, making it unlikely to be the only case.
The patient experienced "mild" symptoms and has now recovered, officials said in a statement.
It is not known at this stage how transmissible the new strain, named H1N2, is, or if there could be other cases in the UK, scientists said.
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H1N1, H1N2 and H3N2 are major subtypes of swine flu A viruses in pigs and occasionally infect humans.
There have been a total of 50 human cases of H1N2 reported globally since 2005.
But none of them are related genetically to this strain seen in the UK.
Swine flu can be passed from pigs to humans via direct contact, but only in rare cases spreads between humans.
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The UKHSA's advice for all respiratory symptoms remains the same - avoid contact with others while they persist, particularly if they are old or have existing medical conditions.
Meera Chand, incident director at UKHSA, said: "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 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, added: "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."
In 2009, there was a pandemic in humans caused by flu strain H1N1, commonly referred to as swine flu.
The H1N1 strain was first detected in April of that year in North Amercia but quickly spread across the US and worldwide.
By the time the WHO declared it a pandemic in June 2009, it had spread to 74 countries and territories.
It killed 457 people in the UK. But it now circulates in humans seasonally, is included in the flu jab, and is not referred to as 'swine flu'.
The WHO declared the pandemic was over in August 2010.
Professor Ian Jones, a virologist at the University of Reading, said: “It’s very unlikely the single case of H1N2 swine flu reported today represents anything more than has been seen in the past.
“And although a single case may not be representative, the fact the individual concerned had a mild infection that resolved without hospitalisation is also in keeping with previous experience.
“We should remember that surveillance programmes can discover infections that might never have been noticed based on case numbers or severity, so a level of reasoned tolerance has to be applied. Not every new agent is a threat.”
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Professor Paul Hunter, a health protection expert from the University of East Anglia, said: “Overall the evidence is that influenza A(H1N2) does not cause any more severe disease than other more commonly circulating types of influenza.
“Also person-to-person transmission does not appear to be very efficient and sustained person-to-person transmission has not been reported so far.”
What are the symptoms of swine flu?
The symptoms of swine flu (H1N1) are similar to those of regular flu.
Symptoms can begin up to five days after exposure to the virus.
These may include:
- Fever
- Chills
- Cough
- Sore throat
- Body or muscle aches
- Headache
- Fatigue
Source: Cleveland Clinic