Neither of the cases has experienced any symptoms of avian influenza and both have since tested negative, the UKHSA confirmed.
The detections do not change the level of risk to human health, which remains very low to the general population, health officials said.
Avian flu infection can follow contamination of the nose and throat from breathing in material on the affected farm or can be true infection. It can be difficult to distinguish these in people who have no symptoms.
Bird flu, also known as H5N1, has spread among poultry and wild birds for 25 years, according to the World Health Organisation (WHO).
Since its emergence in 1996, there has only been rare and non-sustained transmission of bird flu to and between humans. More than 130 cases of avian flu have been recorded in mammals since October 2021.
The cases were detected as part of the UKHSA’s asymptomatic surveillance programme, in which poultry workers are asked to take swabs of their nose and throat which are tested for the presence of influenza virus, during the 10 days after their exposure.
The health agency follows up all individuals who have been in contact with a confirmed human case of avian influenza.
Professor Susan Hopkins, Chief Medical Advisor at UKHSA, 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.”
“Globally there is no evidence of spread of this strain from person to person, but we know that viruses evolve all the time and we remain vigilant for any evidence of changing risk to the population.
“It remains critical that people avoid touching sick or dead birds, and that they follow the DEFRA advice about reporting.”
Those with the highest risk of exposure to avian flu may be offered testing and antivirals to help protect from infection as well as reduce the risk of passing on infection, the UKHSA said.
The death of the unnamed girl in Cambodia was the first known human infection with the H5N1 strain in the country since 2014. The girl lived near a conservation area.
The UKHSA group includes Imperial College’s Professor Neil Ferguson, whose modelling was key to the first national Covid-19 lockdown, as well as UKHSA chief medical officer Dr Susan Hopkins.
Policies being examined by the group include the introduction of lateral flow tests for the disease.