Live Swine Flu map | Advice for British health workers | What if it arrives here? | Global concern | Q&A | Latest Markets reaction | Why the US can't afford panic | Picture slideshow

Authorities from every part of the world were scrambling last night to contain a new strain of swine flu that has killed at least 103 people in Mexico.

The virus has spread across the border to the United States with at least 20 cases confirmed yesterday, prompting the Obama Administration to declare a public health emergency and release 12 million doses of the anti-viral drug Tamiflu. Six cases were also confirmed in Canada and outbreaks are also suspected in Israel, France, Spain and New Zealand.

At least two people were admitted to a Scottish hospital last night as a precaution after they returned from Mexico, and Alan Johnson, the Health Secretary, said that any other travellers coming into Britain with flu-like symptoms would be examined “very, very quickly” by the NHS.

The World Health Organisation said that it was treating the outbreak as “a public health emergency of international concern” and asked all countries to step up screening of passengers. It has, however, put off until tomorrow a decision on whether to raise the alert level to four, on a scale of six, which would signal that health authorities should prepare for a pandemic.

After confirming that at least eight children appeared to have developed swine flu during a school trip to the Mexican resort of Cancún, Dr Thomas Frieden, the New York health commissioner, said: “We are looking at this minute-to-minute, hour-to-hour, day-to-day. What is concerning about this is that it is likely swine flu. Second, at this time, it is spreading from person to person.”

President Calderón of Mexico has assumed new powers to isolate those infected with the flu strain since April 13. About 400 people were being tested for swine flu. He is facing mounting criticism that his Government failed to act fast enough. Although Mexican health authorities noted a sharp rise in flu-like cases in March, they thought that it was the usual winter flu.

One of the greatest concerns is that the new strain seems to target young, healthy adults, the same group affected by Spanish flu, which killed 20 to 50 million people in 1918.

Explore Health

• Expert Advice

• Health Features

• Mental Health

• Alternative Medicine

• Child Health

• Health Club