MEXICO CITY (AP) – Mexico eliminated more reasons to visit the country on Tuesday, putting its pyramids and all other archaeological sites off limits nationwide and closing restaurants in the capital for all but take-out food in an aggressive bid to stop groups from gathering and spreading swine flu.

The outbreak is suspected in 152 deaths and thousands of illnesses in Mexico, and a cluster of illnesses in New York City suggested that the new flu strain has the capacity to continue spreading between humans around the world.

The United States stepped up checks of people entering the country and warned Americans to avoid nonessential travel to Mexico. Canada, Israel and France issued similar travel advisories. And Cuba suspended flights to and from Mexico, becoming the first country to impose an outright ban on travel to the epicenter of the epidemic.

Argentina soon followed with its own ban, and ordered 60,000 visitors who arrrived from Canada, Mexico and the U.S. in the past 20 days to contact the Health Ministry.

Experts on epidemics said these kinds of government interventions are ineffective, since this flu – a never-before-seen blend of genetic material from pigs, birds and humans to which people have no natural immunity – is already showing up in too many places for containment efforts to make a difference.

Outside Mexico, confirmed cases were reported for the first time as far away as New Zealand and Israel, joining the United States, Canada, Britain and Spain. The U.S. Centers for Disease Control and Prevention said the U.S. has 66 confirmed cases in five states, with 45 in New York, one in Ohio, one in Indiana, two in Kansas, six in Texas and 13 in California.

“Border controls do not work. Travel restrictions do not work,” said WHO spokesman Gregory Hartl, recalling the SARS epidemic earlier in the decade that killed 774.

people, mostly in Asia, and slowed the global economy.

Instead, they say, governments should do more to provide medical help to people with swine flu symptoms, since the virus is proving to be treatable if diagnosed early.

U.S. officials stressed there is no need for panic, noting that flu outbreaks are quite common every year. The CDC estimates about 36,000 people in the U.S. alone died of flu-related causes each year, on average, in the 1990s.

Still, without a solid understanding of where the outbreak began or even how fast it is spreading in Mexico, authorities were focused on preventing people from gathering in groups where mass contagion could result.

Mexico City’s mayor ordered restaurants to limit service to takeouts and deliveries, and closed gyms and swimming pools and restricted access to many government buildings.

The economic toll also spread. Even before the restaurant closings, the capital has lost 777 million pesos ($56 million) a day since the outbreak began, said Arturo Mendicuti, president of the city’s Chamber of Trade, Services and Tourism.

“Of course we don’t like these measures,” he said. “We hope they don’t last.”

In the U.S., President Barack Obama asked Congress for $1.5 billion in emergency funds to fight the illness.

“I fully expect we will see deaths from this infection,” said Richard Besser, acting director of the CDC.

In New York, there were growing signs that the virus was moving beyond St. Francis Preparatory school, where sick students started lining up at the nurse’s office days after some students returned from Cancun.

At the 2,700-student school, the largest Roman Catholic high school in the nation, “many hundreds of students were ill with symptoms that are most likely swine flu,” said Health Commissioner Thomas Frieden. A teacher was one of 28 confirmed cases. And a nearby school with siblings at St. Francis was shut down as well after more than 80 students called in sick.

“It is here and it is spreading,” Frieden said.

Rachel Mele, a 16-year-old at the school, saw her fever break Tuesday for the first time in five days. It had been hovering around 101 since the terrifying night when her parents rushed her to the hospital.

“I could barely even catch my breath. I’ve never felt a pain like that before,” Mele said. “My throat, it was burning, like, it was the worst burning sensation I ever got before. I couldn’t even swallow. I couldn’t even let up air. I could barely breathe through my mouth.”

It is significant that some of confirmed New York cases passed swine flu to others who had not traveled – this suggests the virus can jump from human to human to human, spreading through other countries, said Keiji Fukuda, assistant director-general of the World Health Organization.

“There is definitely the possibility that this virus can establish that kind of community-wide outbreak capacity in multiple countries, and it’s something we’re looking for very closely,” Fukuda said. So-called “community” transmissions are a key test for gauging whether the spread of the virus has reached pandemic proportions.

Mexico opened its national naval hospital to civilians to deal with the still-mounting wave of suspected swine flu cases. Staffers wore goggles, masks and booties as they treated patients who had crowded the waiting rooms and reception areas for a chance to get in.

As Mexico’s caseload grew, complaints were heard throughout the capital of 20 million that the supply of surgical masks was running out.

Scientists hope to have a key ingredient for a vaccine ready in early May, but it still will take months before any shots are available for the first required safety testing. Using samples of the flu taken from people who fell ill in Mexico and the U.S., scientists are engineering a strain that could trigger the immune system without causing illness.

“We’re about a third of the way” to that goal, said Dr. Ruben Donis of the CDC.

U.S. officials said they may abandon the term “swine flu” since the virus blends genetic material from three species, and because many people mistakenly fear they can get it from meat. The outbreak has been a public relations nightmare for the pork industry, and China, Russia and Ukraine are among the countries who have banned imports from Mexico and parts of the U.S.

“It’s killing our markets,” said Francis Gilmore, 72, who runs a 600-hog operation in Perry, Iowa, outside Des Moines, and worries his small business could be ruined by the crisis. “Where they got the name, I just don’t know.”

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