The UK Health Security Agency (UKHSA) has detected a single confirmed human case of influenza A(H1N2)v – a new strain of swine influenza.
Influenza A(H1N2)v is similar to influenza viruses currently circulating in pigs in the UK. This is the first detection of this strain in a human in the UK. As is usual early in emerging infection events, UKHSA is working closely with partners to determine the characteristics of the pathogen and assess the risk to human health.
The case was detected as part of routine national influenza surveillance undertaken by UKHSA and the Royal College of General Practitioners (RCGP). The individual was tested by their GP after experiencing respiratory symptoms. Influenza A(H1N2)v virus was detected by UKHSA using PCR testing and characterised using genome sequencing.
The individual concerned experienced a mild illness and has fully recovered. The source of their infection has not yet been ascertained and remains under investigation. Close contacts of the case are being followed up by UKHSA and partner organisations. Any contacts will be offered testing as necessary and advised on any necessary further care if they have symptoms or test positive. UKHSA is monitoring the situation closely and is taking steps to increase surveillance within existing programmes involving GP surgeries and hospitals in parts of North Yorkshire.
Meera Chand, Incident Director at UKHSA, said: “It is thanks to routine influenza 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.”
Influenza A(H1) viruses are enzootic in swine populations in most regions of the world. When an influenza virus that normally circulates in swine is detected in a person, it is called a ‘variant influenza virus’. H1N1, H1N2 and H3N2 are major subtypes of swine influenza A viruses in pigs and occasionally infect humans, usually after direct or indirect exposure to pigs or contaminated environments. There have been a total of 50 human cases of influenza A(H1N2)v reported globally since 2005; none of them related genetically to this strain. Influenza A(H1N2)v has not previously been detected in humans in the UK. Human infections with swine influenza viruses occur sporadically.
In 2009, there was a pandemic in humans caused by an influenza virus (influenza A H1N1[pdm09]) commonly referred to as ‘swine flu’. That virus contained genetic material from viruses that were circulating in pigs, birds and humans in the 1990s and 2000s. Influenza A H1N1(pdm09) is now circulating in humans seasonally and is no longer referred to as 'swine flu'. It is distinct from the viruses currently circulating in pigs.