- guardian.co.uk, Saturday 25 April 2009 22.09 BST
The World Health Organisation has warned countries to be on alert for any unusual flu outbreaks after a swine flu virus was implicated in possibly dozens of human deaths in Mexico.
The BA employee, who has not been named, has been taken to Northwick Park hospital in Harrow, a hospital spokesman said.
He added: "He has flu-like symptoms and is responding well to treatment. The patient was admitted directly to a side room and the hospital is scrupulously following infection control procedures to ensure there is no risk to any other individual in the hospital."
The man was taken from flight BA242 which landed at 2pm today, a BA spokesman said.
A Health Protection Agency spokesman said: "We are aware of a patient admitted to a London hospital with reported travel history to Mexico.
"As a precautionary measure the patient is being tested for a range of respiratory and other illnesses in line with UK health guidance. At present there have been no confirmed cases of human swine flu in the UK or anywhere in Europe."
A spokesman for Hillingdon Council, which is responsible for the health of people passing through the airport, said: "As the port authority for Heathrow Airport we already have Health Protection Agency doctors in each of the airport's terminals at all times.
"Should we receive instructions from the Department for Health or the Health Protection Agency we will be well placed to respond appropriately."
World Health Organisation director-general Margaret Chan has said the outbreak in Mexico involves "an animal strain of the H1N1 virus".
The flu virus, which is suspected of killing at least 60 people in Mexico, has the potential to become a pandemic, she said.