Global health authorities warned Wednesday that swine flu was threatening to bloom into a pandemic, and the virus spread farther in Europe even as the outbreak appeared to stabilize at its epicenter. A toddler who succumbed in Texas became the first death outside Mexico.

New cases and deaths finally seemed to be leveling off in Mexico, where 160 people have been killed, after an aggressive public health campaign. But the World Health Organization said the global threat is nevertheless serious enough to ramp up efforts to produce a vaccine against the virus.

"It really is all of humanity that is under threat during a pandemic," WHO Director General Margaret Chan said in Geneva. "We do not have all the answers right now, but we will get them."

It was the first time the WHO had declared a Phase 5 outbreak, the second-highest on its threat scale, indicating a pandemic could be imminent.

The first U.S. death from the outbreak was a Mexico City toddler who traveled to Texas with family and died Monday night at a Houston hospital. U.S. Health and Human Services Secretary Kathleen Sebelius predicted the child would not be the last U.S. death from swine flu.

The virus, a mix of pig, bird and human genes to which people have limited natural immunity, had spread to at least nine countries. In the United States, nearly 100 have been sickened in 11 states.

Eight states closed schools Wednesday, affecting 53,000 students in Texas alone, and President Barack Obama said wider school closings might be necessary to keep crowds from spreading the flu. Mexico has already closed schools nationwide until at least May 6.

"Every American should know that the federal government is prepared to do whatever is necessary to control the impact of this virus," Obama said, highlighting his request for $1.5 billion in emergency funding for vaccines.

Just north of the Mexican border, 39 Marines were being confined to their California base after one contracted swine flu. Senators questioned Homeland Security Secretary Janet Napolitano about her decision not to close the border, action she said "has not been merited by the facts."

Ecuador joined Cuba and Argentina in banning travel either to or from Mexico, and other nations considered similar bans. In France, President Nicolas Sarkozy met with cabinet ministers to discuss swine flu, and the health minister said France would ask the European Union to suspend flights to Mexico.

The U.S., the European Union and other countries have discouraged nonessential travel to Mexico. Some countries have urged their citizens to avoid the United States and Canada as well. Health officials said such bans would do little to stop the virus.

Germany and Austria became the latest countries to report swine flu infections Wednesday, with cases already confirmed in Canada, Britain, Israel, New Zealand and Spain.

In addition to the 160 deaths, the virus is believed to have sickened 2,498 people across Mexico. But only 1,311 suspected swine flu patients remained hospitalized, and a closer look at daily admissions and deaths at Mexico's public hospitals suggests the outbreak may have peaked during three grim days last week when thousands of people complained of flu symptoms.

Scientists believe that somewhere in the world, months or even a year ago, a pig virus jumped to a human and mutated, and has been spreading between humans ever since. Unlike with bird flu, doctors have no evidence suggesting a direct pig-to-human infection from this strain, which is why they haven't recommended killing pigs.

Medical detectives have not zeroed in on where the outbreak began. One of the seven deaths in Mexico directly attributed to swine flu was that of a Bangladeshi immigrant, said Mexico's chief epidemiologist, who suggested that someone could have brought the virus from Pakistan or Bangladesh.

Miguel Angel Lezana, the epidemiologist, said the unnamed Bangladeshi had lived in Mexico for six months and was recently visited by a brother who arrived from Bangladesh or Pakistan and was reportedly ill. The brother has left Mexico and his whereabouts are unknown, Lezana said.

By March 9, the first symptoms were showing up in the Mexican state of Veracruz, where pig farming is a key industry in mountain hamlets and where small clinics provide the only health care.

The earliest confirmed case was there: a 5-year-old boy who was one of hundreds of people in the town of La Gloria whose flu symptoms left them struggling to breathe.

Days later, a door-to-door tax inspector was hospitalized with acute respiratory problems in the neighboring state of Oaxaca, infecting 16 hospital workers before she became Mexico's first confirmed death.

Neighbors of the inspector, Maria Adela Gutierrez, said Wednesday that she fell ill after pairing up with a temporary worker from Veracruz who seemed to have a very bad cold. Other people from La Gloria kept going to jobs in Mexico City despite their illnesses, and could have infected people in the capital.

The deaths were already leveling off by the time Mexico announced the epidemic April 23. At hospitals Wednesday, lines of anxious citizens seeking care for flu symptoms dwindled markedly.

The Mexican health secretary, Jose Angel Cordova, said getting proper treatment within 48 hours of falling ill "is fundamental for getting the best results" and said the country's supply of medicine was sufficient.

Cordova has suggested the virus can be beaten if caught quickly and treated properly. But it was neither caught quickly nor treated properly in the early days in Mexico, which lacked the capacity to identify the virus, and whose health care system has become the target of widespread anger and distrust.

In case after case, patients have complained of being misdiagnosed, turned away by doctors and denied access to drugs. Monica Gonzalez said her husband, Alejandro, already had a bad cough when he returned to Mexico City from Veracruz two weeks ago and soon developed a fever and swollen tonsils.

As the 32-year-old truck driver's symptoms worsened, she took him to a series of doctors and finally a large hospital. By then, he had a temperature of 102 and could barely stand.

"They sent him away because they said it was just tonsillitis," she said. "That hospital is garbage."

That was April 22, a day before Mexico's health secretary announced the swine flu outbreak. But the medical community was already aware of a disturbing trend in respiratory infections, and Veracruz had been identified as a place of concern.

Gonzalez finally took her husband to Mexico City's main respiratory hospital, "dying in the taxi." Doctors diagnosed pneumonia, but it may have been too late: He has suffered a collapsed lung and is unconscious. Doctors doubt he will survive.

Swine flu has symptoms nearly identical to regular flu _ fever, cough and sore throat _ and spreads like regular flu, through tiny particles in the air, when people cough or sneeze. People with flu symptoms are advised to stay at home, wash their hands and cover their sneezes.

While epidemiologists stress it is humans, not pigs, who are spreading the disease, sales have plunged for pork producers around the world. Egypt began slaughtering its roughly 300,000 pigs on Wednesday, even though no cases have been reported there. WHO says eating pork is safe, but Mexicans have even cut back on their beloved greasy pork tacos.

Pork producers are trying to get people to stop calling the disease swine flu, and Obama notably referred to it Wednesday only by its scientific name, H1N1. U.N. animal health expert Juan Lubroth noted some scientists say "Mexican flu" would be more accurate, a suggestion already inflaming passions in Mexico.

Authorities have sought to keep the crisis in context. In the U.S. alone, health officials say about 36,000 people die every year from flu-related causes.

Mexico's government said it remains too early to ease restrictions that have shut down public life in the overcrowded capital and much of the country. Pyramids, museums and restaurants were closed to keep crowds from spreading contagion.

"None of these measures are popular. We're not looking for that _ we're looking for effectiveness," Mexico City Mayor Marcelo Ebrard said. "The most important thing to protect is human life."

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Associated Press writers Olga Rodriguez in Oaxaca, Mexico, E. Eduardo Castillo in Mexico City, Lauran Neergaard and Tom Raum in Washington, Juan A. Lozano in Houston, Mike Stobbe in Atlanta, Patrick McGroarty in Berlin and Maamoun Youssef in Cairo contributed to this report.