NEW YORK — The global swine flu outbreak worsened today as hundreds of students at a New York school fell ill and federal officials said they expected to see U.S. deaths from the virus.

Cuba suspended flights to and from Mexico, becoming the first country to impose a travel ban to the epicenter of the epidemic.

The mayor of Mexico City cracked down further on public life, closing gyms and swimming pools and ordering restaurants to limit service to takeout.

Confirmed cases were reported for the first time in New Zealand and Israel, which joined the United States, Canada, Britain and Spain.

Swine flu is believed to have killed more than 150 people in Mexico. The Centers for Disease Control and Prevention said the U.S. has 68 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.

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

That was echoed by Homeland Security Secretary Janet Napolitano.

"It is very likely that we will see more serious presentations of illness and some deaths as we go through this flu cycle," she said.

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

In New York, there were growing signs that the virus was moving beyond St. Francis Preparatory school, where sick students started lining up last week at the nurse's office. The outbreak came just days after a group of students returned from spring break in Cancun.

At the 2,700-student school, the largest Roman Cathlic high school in the nation, "many hundreds of students were ill with symptoms that are most likely swine flu," said Health Commissioner Thomas Frieden. The cases haven't been confirmed.

Twelve teachers reported flu-like symptoms as well, said the principal, Brother Leonard Conway.

A nearby public school for special education students was shut down after more than 80 students called in sick. Frieden said that some of the students have siblings at St. Francis.

"It is here and it is spreading," Frieden said.

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

The increase in cases was not surprising. For days, CDC officials said they expected to see more confirmed cases — and more severe illnesses. Health officials across the country stepped up efforts to look for symptoms, especially among people who had traveled to Mexico.

U.S. scientists hope to have a key ingredient for a vaccine ready in early May, but it still will take a few 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.

The economic toll also spread further. Economic officials said the Mexico City economy is losing $57 million a day amid a shutdown that includes schools, state-run theaters and other public places.

Cuba announced a 48-hour ban on flights to and from Mexico, except in "exceptional cases." The last flight from Mexico touched down in Havana around 4 p.m., then returned to Mexico City with a plane load of passengers before the two-day suspension officially took effect.

The U.S. 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.

But for all the government intervention, health officials suggested the flu strain was spreading so fast that efforts to contain it might prove ineffective. Around the world, officials hoped the outbreak would not turn into a full-fledged pandemic, an epidemic that spreads across a wide geographical area.

"Border controls do not work. Travel restrictions do not work," said World Health Organization spokesman Gregory Hartl, recalling the SARS epidemic earlier in the decade that killed 774 people, mostly in Asia, and slowed the global economy.

The pork industry was dealing with a public relations nightmare over the virus, which is a never-before-seen hybrid of human, swine and bird influenza that is widely called swine flu.

Public health officials have said people cannot get sick from eating pork, but some countries, such as China, Russia and Ukraine, have banned imports from Mexico and parts of the U.S.

U.S. officials said they may abandon the term "swine flu" for fear of confusing people into thinking they could catch it from eating pork.

"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."

Gov. Arnold Schwarzenegger declared a state of emergency to help California agencies coordinate efforts in response to the outbreak. He cautioned, however, that "there is no need for alarm."

In New York, the city called on the CDC for additional resources to investigate the outbreak at St. Francis Prep.

About 1,500 students replied to surveys sent out by the health department about the outbreak, helping the city get a better sense of how the virus is spreading. Some students have complained of sudden nausea; others dealt with high fever, sore throats, coughs and aches.

Rachel Mele and her mother, Linda, were relieved when the 16-year-old's fever broke today for the first time in five days. It had been hovering around 101.

The family could finally breathe easy — a relief after a terrifying night Thursday in which Mele's parents bundled her into the car and rushed her to the hospital when they realized she was having trouble breathing.

"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."