An EDF worker based in Somerset has tested positive for coronavirus after returning to China.
The 35-year-old Chinese national left the UK after concluding a placement with the energy firm.
He developed symptoms of Covid-19 two days later and was confirmed to have the virus on March 1.
Public Health England and EDF are now tracing people who had contact with the man in the weeks before he left the UK.
In a statement, Public Health England said: “Authorities in China report that the person did not have symptoms whilst in the UK, so the risk to other people in the UK is considered to be very low.
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“To help understand how this person may have become infected, PHE is working with EDF to identify anyone with symptoms who may have come into contact with the case in the weeks before they left.”
It is understood the man had been in the UK for a number of months before returning to China.
Information posted online by Chinese authorities said the man, wearing a mask, flew with Cathay Pacific from London to Hong Kong on February 27.
He then took a ferry to China, at which time his temperature was normal, and then travelled in a taxi to his home in Futian District.
The man developed symptoms on February 29 and was taken to hospital, then placed in isolation.
He tested positive for Covid-19 at 12.40am on March 1, Chinese authorities said.
EDF is now tracing people who may have been in contact with the man between February 15 and 27 to see if they have shown symptoms.
An office of the company, Bridgewater House in Finzels Reach, Bristol, has been deep-cleaned as a precaution.
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An EDF Energy spokesman said: “Public Health England has advised that there is a very low risk to Hinkley Point C employees or their contacts from the colleague who developed coronavirus after returning to China.
“Public Health England is working with us to understand how the individual could have become infected.
“The four workers who self-isolated at Hinkley Point C last week do not have coronavirus and have returned to work.
“The project continues to operate as usual.”
In a statement posted online, Hong Kong authorities said people who took the same flight as the man, or were on the ferry with him, are urged to call the city’s Centre for Health Protection.
The World Health Organisation says estimates of the incubation period for Covid-19 range from one day to two weeks, though it is most commonly around five days.