#17,811
Two weeks ago the UKHSA Announced the 1st H1N2v (Swine Variant) Infection In the UK, in an individual who apparently tested positive in early November. The patient reportedly had mild illness and has recovered, but their source of infection was unknown.
H1N2v is a swine variant influenza A virus that has been identified in other countries, including the United States, more than 4 dozen times over the past decade.
Eleven days ago (Dec 1st) we saw the UKHSA release unusually stringent Guidance For Public On Possible H1N2v Exposure, and the WHO released their DON (Disease Outbreak News) summary on the lone identified case.
As we've discussed often, detection of sporadic novel flu infections in the general population is often a matter of luck, even in countries with robust surveillance and reporting capabilities.
Last March, in UK Novel Flu Surveillance: Quantifying TTD, the UKHSA estimated their Time To Detection (TTD) could require 3-10 weeks, and the infection of dozens (or even hundreds) of people, before community spread could be established.
And this is for the UK. The TTD in many less-developed regions would presumably take longer.
Today the UKHSA has released a brief update and a more lengthy technical report/risk assessment, indicating that no additional cases have been identified, but that enhanced surveillance will continue for the next few weeks.
UKHSA publishes update on influenza A(H1N2)v
No further cases of influenza A(H1N2)v have been found. Enhanced surveillance will continue over the coming weeks.
From:UK Health Security Agency Published11 December 2023
The UK Health Security Agency (UKHSA) has published its investigation findings on the recent case of influenza A(H1N2)v.
The case was detected as part of routine national flu surveillance undertaken by UKHSA and the Royal College of General Practitioners (RCGP).
The virus was identified by UKHSA on 23 November using genome sequencing, the first time a human case of this particular virus has been confirmed in the UK.
Rapid work has been underway to learn more about the virus and its characteristics, including how it may have been acquired and whether it may have spread.
There remains only one human case of influenza A(H1N2)v in England. The case was an otherwise well person over 75 years of age, who has recovered fully.
Although the virus is similar to those detected in pigs in England and the case lives in a region containing pig farms, no direct contact between the case and any animal was reported.
No further cases have been detected through investigations, including follow-up of contacts to date and enhanced surveillance through local GP practices and hospital trusts.
Enhanced surveillance will continue over the coming weeks as a precaution.
UKHSA Incident Director Dr Meera Chand said:
This is the first time we have detected this virus in humans in the UK. Since the virus was confirmed we have been working rapidly to learn more about it and how it might have been acquired.
Investigations to date have not identified any further human cases and sporadic cases of influenza from swine viruses are known to occur.
The identification of this case highlights the importance of our flu surveillance and genomic sequencing in helping us to identify and learn more about new viruses.
UK Health Security Agency press office
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London
E14 4PU
Email ukhsa-pressoffice@ukhsa.gov.uk
The a link, and some excerpts from the full report follow:
Influenza A(H1N2)v: rapid technical assessment
Published 11 December 2023
Situation update
A human case of influenza A (H1N2)v clade 1B.1.1 was detected in England through routine community respiratory virus surveillance. The case is an otherwise well person over 75 years of age, who recovered fully. Although the virus was similar to those detected in pigs in England and the case lives in a region of England containing pig farms, no direct contact between the index case and any animal was reported.
UKHSA with APHA and Defra, the Francis Crick Institute, local NHS partners and the local authority therefore investigated:
1. To determine the source of infection, backwards contact tracing and assessment of potential locations for animal to human spillover in the vicinity of the case were undertaken. Although the case lives in an area of the country which contains pig farms and in proximity to sites containing animals (including a veterinary facility and a live auction market) no direct link or chain of transmission could be identified between the case and any animal. Environmental sampling is ongoing.
2. To identify any potential human to human transmission: contact tracing, polymerase chain reaction (PCR) testing and serology are being used. One household contact and one other contact were symptomatic but their symptoms had already resolved by the time they were identified, and therefore they were not tested whilst unwell. At the time of testing, one of these contacts had a non-influenza respiratory pathogen detected although its significance is unclear given timing with respect to symptoms. To date, no further cases have been detected through the investigations including follow-up of contacts (including precautionary follow up of the contacts of symptomatic contacts). Serological assessment is ongoing.
3. To rule out any local community transmission, enhanced surveillance is being conducted (community and hospital). Following the index case, no further cases have been detected to date through enhanced surveillance through local GP practices (Table 1) and hospital trusts, but this will continue for a further 4 weeks.
Exploratory studies have also been initiated to improve knowledge of spillover risk and to develop capability for future events, including an assessment of the potential of wastewater testing, environmental studies of potential spillover locations, and protocols for surveillance of occupational groups with relevant animal exposure. Work is also ongoing to assess the ability of currently available diagnostic assays to detect this strain.
This report provides a summary of the assessment that UKHSA makes for novel or emerging influenza viruses. Data used for the assessment was provided by UKHSA, APHA, and the Worldwide Influenza Centre at the Francis Crick Institute.
(SNIP)
Human to human transmission
There is no virologically confirmed human-to-human transmission. The human case viral genome is closely related to circulating viruses in pigs (‘moderate confidence’) and the mutational profile where it can be interpreted is consistent with a hypothesis of recent emergence (‘low confidence’).
The presence of a case without direct contact with animals, and the presence of a symptomatic household contact, mean that some limited degree of human-to-human transmission may have occurred (‘low confidence’).
No onwards transmission has been detected through PCR testing of contacts (‘low confidence’; given the normal surveillance lag time in identifying the influenza variant, most testing was relatively late compared to potential exposure and serological assessment is in process and may change this assessment).
No other cases have been detected through UKHSA enhanced community surveillance, including amongst 133 acute respiratory illness patients swabbed between 1 October and 1 December at the nearest 5 RCGP sentinel practices. This is the first ever detection of a non-human influenza strain through RCGP surveillance.
Influenza A(H1N2) sporadic human cases have been detected internationally, usually with direct links to swine, although these are not within the same specific clade.
Severity of disease
No conclusions can be drawn from a single case.
Antigenic characteristics
Based on rapid assessments undertaken by Worldwide Influenza Centre (WIC, FCI), currently available H1 subtype 1B lineage candidate vaccine viruses (CVVs) for prepandemic preparedness, would be unlikely to afford protection against the H1 1B.1.1 swine influenza A viruses detected in the UK.
Additionally, based on a small panel of UK sera taken pre- and post- vaccination with the 2023 to 2024 influenza vaccine, the current seasonal influenza vaccine will likely not afford protection against the H1 1B.1.1 swine influenza A viruses detected in the UK. Further assessment is underway.
While a swine variant virus like H1N2v would likely have a far less severe impact compared to an avian flu like H5N1, it wouldn't necessarily be as mild as the 2009 H1N1 pandemic.
Hopefully this case was a one-off, dead-end infection.
But the swine source for these viruses remains, and future spillovers into humans - in the UK, and elsewhere in the world - may have more `legs'.
