May 1 - Swine flu reached 11 countries, as governments closed schools, planned for vaccine production and tapped emergency stockpiles of antiviral medicine.

More than 250 people have swine flu confirmed by genetic tests, according to the World Health Organization's Web site. Hundreds more cases are suspected in New York, Mexico and Australia. The health agency said thousands of samples from sick patients are backlogged for testing, and disease trackers are looking at whether an outbreak in Spain should trigger a declaration of a pandemic.

The Geneva-based WHO raised its six-tier alert to 5 on April 29 and said that a move to the next and final level, for the world's first influenza pandemic since 1968, may soon be made. The agency urged countries to make final preparations against a disease that may sweep across the globe, preying on a world population that has no natural immunity to the new virus.

"What the public health community can and must do is provide the very best information," said Michael Osterholm, director of the Center for Infectious Disease Research and Policy, at the University of Minnesota, in Minneapolis, in a telephone interview. "We make general guideline recommendations, but it's all local leaders who decide."

Fort Worth, Texas, closed 144 public schools with 80,000 students after one child came down with swine flu. Citigroup Inc. disinfected a New York office building when a worker became ill, and as many as 400,000 pigs are being slaughtered in Egypt.

Near Pandemic

As the number of people sick with swine flu continued to rise, an outbreak in Spain may show the virus is establishing itself beyond Mexico and the U.S., approaching the World Health Organization's definition of a pandemic. The agency needs evidence of sustained human-to-human transmission outside North America.

Spain confirmed 13 cases, including one person who hadn't been to Mexico. WHO raised the alert to level 5 after swine flu took root in New York. It was the second elevation this week.

The number of new cases in Mexico is "stabilizing," Jose Cordova, Mexico's health minister, said yesterday in Mexico City.

A phase 5 warning is "a strong signal that a pandemic is imminent" with little time left for preparation, according to the Web site of the WHO, an agency of the United Nations. It's based on the determination that the disease is established in communities in two countries in the same WHO region.

Schools Closed

In the U.S., at least 298 schools closed, leaving parents to find other arrangements for 172,000 students, according to the Education Department. The Centers for Disease Control and Prevention, a U.S. agency based in Atlanta, raised its flu count to 109, including a 22-month-old child who died April 27 at a Houston hospital.

A Citigroup Inc. employee in New York and a World Bank employee in Maryland were preliminarily diagnosed with swine flu. One of Barack Obama's aides who traveled to Mexico as part of last month's presidential trip, along with his family, showed symptoms.

The World Bank yesterday gave $25.6 million to Mexico for antiviral drugs, medical supplies and equipment to test for swine flu. The payment is the first of $205 million the World Bank pledged on April 26 to help Mexico cope with the outbreak, according to the bank's news release.

Travel Restrictions

Margaret Chan, WHO's director-general, said travel restrictions won't slow the flu. Countries should ready emergency plans, she said at the organization's Geneva office on April 29.

Batches of seed virus are being developed for potential vaccine production, according to WHO. Paris-based Sanofi-Aventis SA, Baxter International Inc. of Deerfield, Illinois, and GlaxoSmithKline Plc, of London, are talking with world health authorities about how to produce a vaccine.

Production of shots against seasonal flu will be completed before swine flu vaccine production begins, if that decision is made, Richard Besser, acting head of the CDC said yesterday.

The CDC deployed antiviral drugs from the U.S. stockpile to 9 of 11 states with confirmed cases, Besser said. Shipments to the two other states should be finished by May 3. The CDC is adding more communications staff and equipment to field 4,000 calls, 2,000 e-mails and 6 million to 8 million visits to its Web site a day, he said.

Mexico Toll

The U.S. will spend $251 million to buy 13 million courses of antiviral treatments to replenish its stockpile, Health and Human Services Secretary Kathleen Sebelius said yesterday in a statement. The White House said 20 states have probable or confirmed cases.

In Mexico, where the toll is highest, 159 people may have died from the malady, according to government officials, with 97 cases and at least seven deaths confirmed by WHO-approved laboratory tests.

A "worrisome sign from Mexico was the relatively young healthy adults" succumbing to the virus, said Anne Schuchat, interim deputy director of the CDC science and public health program, said yesterday in Congress. She said the average age of those in the U.S. confirmed to have the flu is 22.

WHO's statistics, which lag behind those reported by national and local agencies, showed confirmed cases in the U.S., Mexico, Canada, Austria, Germany, the Netherlands, Switzerland, Israel, Spain, the U.K. and New Zealand.

Spain Question

Disease trackers are trying to determine whether the new virus, known formally as influenza A (H1N1), is spreading efficiently in Spain, said Dick Thompson, a spokesman for WHO.

Among the 13 cases in Spain, at least one patient hadn't traveled to Mexico, Thompson said. One case "confirmed to us that there's some community transmission beginning," he said. "The virus is becoming established in another area. It's this new single case that is especially worrying."

The last pandemic, 41 years ago, killed 1 million people and was mild compared with the global outbreak of 1918, which may have killed as many as 50 million.

President Obama asked Congress this week for $1.5 billion to battle an outbreak, and said parents should plan for school closings. Texas Governor Rick Perry declared a disaster, a "pre-emptive" measure to facilitate emergency preparations and seek federal reimbursement. California Governor Arnold Schwarzenegger declared a state of emergency.

Pigs are Safe

Swine flu infections in people aren't related to exposure to pigs, and properly prepared pork is safe to eat, said Keiji Fukuda, WHO assistant director-general for health security and environment.

The three main seasonal flu strains -- H3N2, H1N1 and type- B -- cause 250,000 to 500,000 deaths a year globally, according to WHO. The new flu's symptoms are similar, including fever and coughing, nausea and vomiting, according to the CDC, the U.S. agency. It appears to be causing more diarrhea than seasonal flu, WHO said.

The U.S. can expect more hospitalizations and deaths, Sebelius said. Authorities advised hand-washing, hygiene and staying home if sick as the most effective ways to control the outbreak.

A Marine is recovering after being confirmed sick with the virus, and another 37 Marines are being "watched and tested" at a base with 15,000 personnel in 29 Palms, California, Marine Corps Commandant General James Conway said at the Pentagon.