MEXICO CITY AND LOS ANGELES — International officials Saturday declared the swine flu outbreak in Mexico and the U.S. a "public health emergency" as new cases were reported on both sides of the border and fears grew of a possible global epidemic.
The Mexican government indicated that the outbreak was more severe than originally acknowledged, announcing that more than 1,300 people are believed to have been infected. The virus, which the World Health Organization's top official said had "pandemic potential," is now suspected in the deaths of 81 Mexicans, Health Secretary Jose Angel Cordova said.
Also Saturday, the Mexican government gave itself extraordinary powers to quarantine and forcibly treat infected people and to search homes and intercept suspected flu sufferers on public transport.
The emergency decree follows measures that have included the closing of schools in the worst-affected areas until May 6, and the temporary shutdown of museums, clubs and theaters in Mexico City. Hundreds of concerts, private parties and other events were canceled as federal and local officials urged people to avoid large gatherings.
In the United States, a new swine flu case was discovered Saturday in California and two in Kansas, bringing to 11 the number of confirmed incidents of the disease north of the border. All patients have recovered. Eight schoolchildren in New York City are suspected to have a form of swine flu.
At the national Centers for Disease Control and Prevention in Atlanta, Dr. Anne Schuchat said the agency expected more cases and that containment was "not feasible."
"Having found the virus where we have found it, we are likely to find it in many more places," Schuchat told reporters in a telephone news conference. "It is clear that this is widespread, which is why we do not think we can contain spread of this virus."
Many in Mexico City took heed of the health warnings. A city of 20 million people can't ever really be a ghost town. But on a warm, sunny Saturday, only a fraction of the crowds that normally converge on this metropolis' parks and plazas were out and about.
People either stayed home, limited their weekend wanderings or wore masks in hopes they would be protected.
"Maybe it does some good," said Yolanda Flores, 40, a vendor who was arranging embroidered blouses at a stand in downtown Mexico City. She spoke through a loose blue paper mask, one of thousands distributed free by soldiers at metro stations and in the massive central Zocalo, or square.
A gallery opening for eminent artist Gabriel Orozco went ahead as scheduled, with patrons appearing somewhat carefree, sipping beer and juice. But some expressed concern.
"There is a lot of risk," said Anabell Villareal, a 45-year-old businesswoman in tight black jeans who had artfully draped a scarf across her mouth. "We are on alert. But by taking precautions we can continue to live with other people."
For many Mexicans, initial alarm over the outbreak was giving way to anger over the health crisis and skepticism about how the government was handling it. Mexico's flu season was intense and people were dying long before the government sounded the alarm Thursday, after a Canadian testing laboratory identified the unique strain, a mix of human, bird and swine flu viruses.
"The problem is this government never tells you the truth," said lawyer Jose Fernandez, striding mask-free through the posh Polanco neighborhood. "We don't know what's real and what isn't, just how serious this is, at what point they knew about it. . . . And it makes Mexico look bad."
Fernandez had just eaten breakfast with his two sons, Gonzalo, 16, and Pepe, 10, and they were taking a walk. The boys, however, were wearing masks. Just in case.
The only mask that Julio Rojas Ruiz had put on his 8-year-old son was a bright red plastic version of those used by Mexican wrestlers.
"The government is just trying to distract us from other problems, like the economic crisis," he said. "Or maybe it's even worse than they're saying?"
The World Health Organization on Saturday declared that the outbreak of the unique strain of swine flu is a "public health emergency of international concern."
Dr. Margaret Chan, director-general of WHO, said the outbreak "has pandemic potential" because it appears to be transmitted from human to human. But she noted that it was far too early to predict whether a pandemic would occur.
In London, a British Airways crew member was taken to a hospital as a precaution after developing flu-like symptoms on a flight from Mexico City, the airline said Saturday, Reuters news agency reported.
In the United States, CDC field teams are assisting local investigators in California, Texas and Mexico, officials said.
The toll appears to be rising steadily in Mexico. On Saturday, 16 states -- twice the number of just two days ago -- were reporting suspected swine flu cases. Almost all of the deaths so far have been in Mexico City and Mexico and San Luis Potosi states.