Efforts are being made on an international scale to stop the spread of a deadly outbreak of swine flu.
Government officials in Britain have met for emergency discussions over the threat posed by the new human strain of a virus usually associated with pigs.
More than 80 people have died after contracting the H1N1 strain in Mexico and outbreaks have also been reported in New Zealand, Spain and the US.
Two people from Scotland are currently undergoing tests after displaying "flu-like symptoms" following a trip to Mexico.
No cases of swine flu have been confirmed in Britain, and a man taken to hospital in London after arriving at Heathrow from Mexico City is clear of the virus, Health Secretary Alan Johnson confirmed.
He stressed that any travellers arriving in the UK with flu-like symptoms would be examined "very, very quickly" by the NHS.
The NHS has a stockpile of more than £500m worth of the Tamiflu antiviral drug, which has proved effective on patients in Mexico, and scientists are currently developing a vaccine against the new strain, said Mr Johnson.
The Department of Health said it had enough antiviral stocks to provide treatment for 50% of the population should they become ill.