In November 2023 the UKHSA stated that a single human case of influenza A(H1N2)v has been detected in the UK through routine surveillance. Reporting that it is “working closely with partners” to characterise the pathogen and assess the risk to human health, UKHSA reassures the public that the individual experienced only a “mild illness” and has made a full recovery. However, this is the first detection of this strain of flu in a human in the UK, and investigations will continue to identify the source of infection.
What is influenza A(H1N2)v?
Influenza A(H1) viruses are “enzootic in swine populations” in “most regions of the world”. However, UKHSA states that when an influenza virus that “normally circulates in swine” is identified in a person, it is known as a “variant influenza virus”. H1N1, H1N2, and H3N2 are “major subtypes” of swine influenza A viruses that circulate in pigs and occasionally infect humans.
Although there have been 50 human cases of influenza A(H1N2)v reported globally since 2005, none of them have been genetically related to this strain. Furthermore, it has not previously been detected in humans in the UK.
Routine surveillance
UKHSA suggests that routine national flu surveillance carried out by UKHSA and the Royal College of General Practitioners (RCGP) detected the case. The infected individual was tested by their GP after presenting with respiratory symptoms. A PCR test detected the virus, and it was characterised with genome sequencing.
Action and advice
As close contacts are followed up by UKHSA and partner organisations, UKHSA assures the public that any contacts will be offered tests “as necessary” and will be “advised on any necessary further care” if symptoms arise or tests return positive.
“People with any respiratory symptoms should continue to follow the existing guidance; avoid contact with other people while symptoms persist, particularly if the people they are coming into contact with are elderly of have existing medical conditions.”
UKHSA states that it will increase surveillance within existing programmes in parts of North Yorkshire. Incident Director at UKHSA, Meera Chand, reflected that “thank to routine flu surveillance and genome sequencing” we have detected the virus for the first time in humans in the UK.
“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 individuals acquired the infection and to assess whether there are any further associated cases.”
Christine Middlemiss, Chief Veterinary Officer, recognises 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.”
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