World Health Organisation experts stopped just short of declaring a formal swine flu pandemic today after news that a Mexican toddler had died in Texas and as Spain confirmed its first case in a person who had not visited Mexico.

The UN health agency has been closely monitoring the progress of the new H1N1 virus to see whether there was sustained person-to-person transmission outside Mexico, where the outbreak appears to have started.

Once there is, the WHO will notch up its threat alert to declare a phase five pandemic, one step short of a phase six or global pandemic. "We are moving that way, but I don't think we are there yet," Keiji Fukuda, the WHO assistant director-general, said tonight.

More than 200 schoolchildren in Devon were being given anti-viral drugs - and an unexpected week off school - today to prevent an outbreak of swine flu after a 12-year-old girl tested positive for the potentially deadly flu virus - one of five cases now confirmed in Britain.

The girl, from Paignton, near Torbay, flew home from Mexico last week on the same plane as two Scottish honeymooners who were the UK's first swine flu cases. Iain and Dawn Askham are recovering well in an isolation ward at Monklands Hospital in Airdrie, Lanarkshire.

The other two British cases were a 41-year-old woman from Redditch and a 22-year-old man in London. Alan Johnson, the Health Secretary, said that all were responding well to treatment, as he announced that the Government had ordered millions more doses of the anti-viral Tamiflu so that it will be able to cover some 50 million people.

"We'll make sure that we are as well prepared as any country in the world," Mr Johnson added.

The evidence that the outbreak is escalating is not clear-cut, however. American officials reported the first swine flu fatality outside of Mexico, but it transpired that a 23-month-old baby boy who died in hospital in Houston was a resident of Mexico taken ill while visiting relatives in the town of Brownsville.

As Germany and Austria confirmed their first cases, Spain said that it now had ten confirmed cases, including one who was infected through contact with another person recently returned from Mexico.

“Until now, every person who has been affected had recently visited Mexico, except one of them in Catalonia who is the first confirmed case of this type in Spain, who has been indirectly infected,” said Trinidad Jimenez, the Health Minister.

Mexican authorities say that 159 people have been killed there by the new virus there. The death in Texas was the first outside Mexico, and initially appeared to mark a dangerous new milestone in the progress of the virus.

Dr Fukuda said WHO experts - including doctors in Mexico and the US - had been meeting via teleconference to build up a scientific profile of the virus, which tends to provoke a relatively mild illness consistent with seasonal influenza infection.

He said that it was still possible that the epidemic would "suddenly stop for unknown reasons" or that it would continue on a mild level. "It's also possible that we could see more serious cases," he said. "We don't know who this will evolve."

Taking a different tack in the battle against the disease, President Mubarak of Egypt ordered the slaughter of up to 400,000 pigs in his country, which belong to and are eaten by Egypt's large Coptic Christian minority.

The move left Christian farmers, many of them poor slum-dwellers, up in arms and was dismissed as "a real mistake" by Joseph Domenech, chief veterinary officer at the UN's Food and Agriculture Organisation. "There is no reason to do that. It’s not a swine influenza, it’s a human influenza," he said.

President Obama, who was today marking his 100th day in office, has asked Congress to approve $1.5 billion in funding to help tackle swine flu.

"Every American should know that the federal government is prepared to do whatever is necessary to control the impact of this virus," he said. "This is obviously a serious situation, serious enough to take the utmost precautions."

He added: ""There are also steps that Americans can take individually. Keep your hands washed, cover your mouth when you cough, stay home from work if you are sick and keep your children home from school if they are sick."

That echoed the advice from UK medical authorities always to use tissues when sneezing, to dispose of the tissues afterwards and wash hands regularly.

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