MEXICO CITY (Reuters) - A new virus has killed up to 149 people in Mexico and the World Health Organization moved closer on Monday to declaring it the first flu pandemic in 40 years as more people were infected in the United States and Europe.The WHO raised its pandemic alert level for the swine flu virus to phase 4, indicating a significantly increased risk of a pandemic, a global outbreak of a serious disease. The last such outbreak, a "Hong Kong" flu pandemic in 1968, killed about 1 million people.
Although the new flu strain has so far killed people only in Mexico, there were more than 40 confirmed cases in the United States, including 20 at a New York City school where eight cases were already identified.
Spain became the first country in Europe to confirm a case of swine flu when a man who returned from a trip to Mexico last week was found to have the virus.
Texas health authorities confirmed a third case of swine flu at a school near the Mexican border and California said it now had 11 confirmed cases.
The U.S. State Department and the European Union urged citizens to avoid non-essential travel Mexico and other areas affected by swine flu. Mexican Health Minister Jose Angel Cordova said the outbreak was now suspected of having killed 149 people and warned the number of cases would keep rising.
Thirty-three million Mexican schoolchildren will be off school until the middle of next week as authorities seek to contain the outbreak. Schools in the sprawling capital had already been closed but the government ordered classes canceled across the country until May 6.
Most of the those who died were between 20 and 50 years of age, an ominous sign because a hallmark of past pandemics has been the high rate of fatalities among healthy young adults.
Worldwide, seasonal flu kills between 250,000 and 500,000 people in an average year but the new strain worries experts because it spreads rapidly between humans and there is vaccine for it.
A New Zealand teacher and a dozen students who recently traveled to Mexico were being treated as likely mild cases.
In the first confirmed cases in Britain, Scotland's health minister said two people tested positive for swine flu and were being treated under isolation near Glasgow.
Suspected cases were also reported in France, Norway, Germany, Sweden and Israel.
Large numbers of Mexicans made it to work in the capital despite the flu outbreak. Traffic in the city of 20 million was brisk as workers, many in surgical masks, packed buses. "I preferred to come by car instead of public transport because I didn't want to be in contact with so many people," said 25-year-old graphic designer Andres Beltran.