Public health officials said that avian influenza had been detected in two poultry workers in England but that there was no evidence of human-to-human transmission.
Detection of the A (H5) strain of avian 'flu was understood to be linked to an outbreak on a single farm where both individuals had recently worked. The UK Health Security Agency (UKHSA) did not identify the site's location. However, it stressed that the risk to the public remained low.
Neither of the poultry workers had experienced any symptoms of avian influenza and identification was made via an asymptomatic testing programme for people who had been in contact with infected birds. Both affected individuals had since tested negative for the virus.
In a statement, the UKHSA said that based on the timing of the exposures and the test results, one of the workers was likely to have been contaminated via the nose or throat from material inhaled on the farm. Advice from the Health and Safety Executive states that avian 'flu transmission to poultry workers was most likely to occur by direct contact with sick and dead or dying infected birds, or infected bird products, such as droppings and respiratory secretions.
The UKHSA said that in the case of the second farm worker, the route of contamination remained unclear, and a follow-up investigation was underway that included "precautionary" contact tracing.
Public Health Officials Remaining 'Vigilant'
Professor Susan Hopkins, the UKHSA's chief medical advisor, said: "Current evidence suggests that the avian influenza viruses we're seeing circulating in birds around the world do not spread easily to people. However, we know already that the virus can spread to people following close contact with infected birds and this is why, through screening programmes like this one, we are monitoring people who have been exposed to learn more about this risk."
The UKHSA was aware that viruses evolve over time and would "remain vigilant" for any evidence of a change in risk to the general population, Professor Hopkins said.
The asymptomatic surveillance programme involved poultry workers being asked to take swabs of their nose and throat to check for the presence of influenza virus in the 10 days following exposure. Some of the individuals were also offered a finger prick blood test to check for antibodies against avian influenza. People who had been in contact with a confirmed human case of avian influenza were contacted by public health officials, with those at the highest risk of exposures offered testing, as well as antivirals to help prevent them passing infection to others.
The latest outbreak of H5N1 highly pathogenic avian 'flu has been circulating in UK and European bird populations for more than 18 months, with some evidence of a spill over into mammal s.
Cases of human infection have been rare, although one case of the H5 strain involving a poultry farmer in South West England was reported in January 2022.
Commenting on the latest cases for the Science Media Centre , Professor James Wood, head of the Department of Veterinary Medicine at the University of Cambridge, said that the strain of H5N1 infecting wild and farmed birds could occasionally infect people but rarely caused disease, "so it is not surprising that asymptomatic sampling has detected infection in two highly exposed workers". He added: "It will of course be important to sequence the virus in these two workers, and the birds that they were exposed to, to determine whether there are any mutations that might be of specific concern."