The non-UK national was diagnosed with Middle East Respiratory Syndrome coronavirus (MERS-CoV) after being taken to hospital with respiratory symptoms in the US.
The passenger had flown on a British Airways flight from Riyadh in Saudi Arabia to Heathrow on April 24, before transferring to Chicago.
Public Health England (PHE) has contacted UK passengers on BA Flight 262 who were sitting near the affected passenger, but stressed the risk of infection was “extremely low”.
Britons on the flight who become unwell or experience respiratory problems have been urged to contact NHS 111.
PHE is also working with US authorities to trace any UK passengers on the onward flight – American Airlines Flight 99 from London to Chicago.
It is the first case of MERS-CoV in the US, after diagnosis was confirmed by the United States Centre for Disease Control in Indiana.
Since mid-March, 111 people have tested positive in the Jeddah area of Saudi Arabia, WHO figures show – the biggest increase in the MERS-CoV outbreak since it was detected in April 2012.
There have been 401 confirmed cases of MERS-CoV infection in 12 countries including 93 deaths, according to the US Centre for Disease Control.
Three people have died so far in the UK as a result of the infection – including one man who died at the end of June.
PHE said the last case to be detected in the UK was in February last year.
Cases have also been reported in France, Germany, Italy and Greece, across the Middle East in Egypt, Jordan, Qatar, Kuwait and Oman and in other countries including Malaysia, Philippines and Tunisia.
PHE said the period between exposure to MERS-CoV and when symptoms might develop is up to 14 days.
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