A British Airways employee who fell ill with flu-like symptoms on a flight from Mexico does not have the new strain causing worldwide concern, it has been announced.

The member of the cabin crew was quarantined in hospital as soon as the flight landed at Heathrow last night, after complaining of feeling ill.

More than 80 people in Mexico have now died, and more than 1,300 have fallen ill, since the new virus was detected two weeks ago.

With cases now emerging in America, officials from the World Health Organisation are warning this could be another pandemic which sweeps the globe.

Spanish flu -- the worst pandemic -- killed more than 40 million victims, but is not well known because it coincided with the First World War.

The last pandemic, so-called Hong Kong flu, broke out in 1968 and took two years to spread across the world, killing a million people.

Any new pandemic would spread much more quickly.

So far the new strain has puzzled scientists because victims in the USA have suffered relatively mild effects, whereas the virus seems to be far more aggressive in Mexico.

The new virus is not related to bird flu, but has come from pigs -- which often act as incubators for new types of the illness.

Any vaccine would take at least five months to develop and will be in short supply.

The new strain seems to be sensitive to an anti-viral drug called Tamiflu, if given in the early stages.

In the UK the Government has stockpiled Tamiflu in case of a bird flu pandemic. It has enough to treat around 25% of the population.