MEXICO CITY A strain of flu never seen before has killed up to 60 people in Mexico and also appeared in the United States, where eight people were infected but recovered, health officials said on Friday.
Mexico's government said at least 20 people have died of the flu and it may also be responsible for 40 other deaths.
It shut down schools and canceled major public events in Mexico City to try to prevent more deaths in the sprawling, overcrowded capital. Authorities said they had enough antiviral medicine to treat about 1,000 suspected cases reported so far.
The World Health Organization said tests showed the virus from 12 of the Mexican patients was the same genetically as a new strain of swine flu, designated H1N1, seen in eight people in California and Texas.
"Our concern has grown as of yesterday," Dr. Richard Besser, acting director of the U.S. Centers for Disease Control and Prevention told reporters in a telephone briefing.
Global health officials were not ready to declare a pandemic -- a global epidemic of a new and deadly disease such as flu. "So far there has not been any change in the pandemic threat level," Besser said.
But the human-to-human spread of the new virus raised fears of a major outbreak. Mexico's government suspended classes for millions of children in Mexico City, where scared residents rushed out to buy face masks and kept their kids at home.