At Least 16 Dead, Hundreds Ill in Swine Flu Outbreak in Mexico

April 24 -- FRIDAY, April 24 (HealthDay News) -- Mexican officials took extraordinary steps Friday to try to contain a swine flu outbreak that has killed at least 16 people, and possibly dozens more, and sickened more than 900 other people in recent weeks.

World health officials worried that it could mark the start of a flu pandemic, the Associated Press reported.

It's not yet clear if the swine flu virus in Mexico is the same as the virus blamed for seven cases of swine flu in California and Texas. All seven patients have recovered.

The World Health Organization said at least 57 people have died in the outbreak in Mexico, but it wasn't yet clear if this larger number of deaths was due to swine flu, the AP reported.

"We are very, very concerned," said Thomas Abraham, a spokesman for the agency. "We have what appears to be a novel virus and it has spread from human to human." If international spread is confirmed, that meets WHO's criteria for raising the pandemic alert level, he added.

In response to the outbreak, Mexico City closed schools -- from kindergartens to the university level -- across the metropolis of 20 million people on Friday, and urged people with flu symptoms to stay home from work, The New York Times reported.

"We're dealing with a new flu virus that constitutes a respiratory epidemic that so far is controllable," Health Minister Jose Angel Cordova told reporters late Thursday, after meeting with President Felipe Calderon and other top officials. He said the virus had mutated from pigs and had at some point been transmitted to humans, the Times said.

While Mexico's flu season is usually over by now, health officials noticed a sizeable uptick in flu cases in recent weeks. The World Health Organization reported about 800 cases of flu-like symptoms in Mexico in recent weeks, most of them among healthy young adults, with 57 deaths in Mexico City and three in central Mexico, the Times said.

That could be worrisome. Seasonal flus usually strike hardest at infants and the elderly, but pandemic flus -- such as the 1918 Spanish flu -- often strike young, healthy people, the newspaper reported.