MEXICO CITY — International officials warned Saturday that a swine flu outbreak could become a global epidemic as new cases were reported north and south of the border.
The Mexican government indicated that the outbreak was more severe than originally acknowledged, announcing Saturday that more than 1,300 people are believed to have been infected. The virus, which the top official of the World Health Organization said had "pandemic potential," is now suspected in the deaths of 81 people in Mexico.
The Mexican government gave itself extraordinary powers to be able to search private homes for sick people, intercept them on public transport, quarantine them and force them to have treatment.
In the United States, health officials reported that at least eight students at a private high school in New York City had "probable" swine flu, and confirmed two new cases in Kansas and one in California, bringing the total number of confirmed U.S. cases to 11. All recovered or are recovering; at least two were hospitalized.
The director general of the World Health Organization, Margaret Chan, said the "situation is evolving quickly." The WHO asked countries around the world to step up reporting and surveillance of the disease and implement a coordinated response to contain it.
"This is a serious situation that must be watched very carefully," Chan said. "It has pandemic potential."
The virus — a combination of swine, bird and human influenza — nearly brought Mexico City to a halt. Normally congested downtown streets were almost empty. Bars and schools have been closed, and Catholic Masses were canceled. Two big soccer matches today will be played in front of TV cameras, but with no live crowds.
"This is a serious moment for the nation," President Felipe Calderon said.
Soldiers and health workers patrolled airports and bus stations, and tried to corral people who may be infected, as it became clearer that the government may have been slow to respond to the outbreak.
Officials noticed a threefold spike in flu cases in late March and early April, but they thought it was a late rebound in the normal flu season. The first recorded death occurred in southern Oaxaca state April 13, but testing did not alert doctors to the new strain until samples were sent to the U.S. Centers for Disease Control and Prevention on April 18.
The U.S. Embassy said the United States has not imposed travel constraints to and from Mexico but was suspending the processing of visas and other services through Wednesday to avoid creating crowds.
But with confirmed swine flu cases in at least six states, the efforts seemed unlikely to stop the spread of the disease. Particularly difficult in a metropolis as crowded as Mexico City was the embassy's advice that maintaining "a distance of at least 6 feet from other persons may decrease the risk of exposure."
The deaths are of particular concern to authorities because the victims have tended to be young, healthy adults, whereas garden-variety flu mostly kills infants and the elderly.
Asian officials were on alert today, with some checking passengers and pork products from Mexico. At Tokyo's busy Narita airport, a device at the gate for flights from Mexico measured passengers' temperatures.
President Barack Obama's health is fine a little more than a week after he traveled to Mexico, the White House said Saturday. Mexican museum director Felipe Solis died last week, days after accompanying Obama on a museum tour on April 16. Health Secretary Jose Cordova said Solis had a pre-existing illness and died of pneumonia unrelated to flu.