Mexican and U.S. officials are taking emergency steps to contain the possible outbreak of a new multi-strain of swine flu that has killed at least 20 people and may be responsible for scores of other deaths.
Mexican health officials confirmed at least 20 deaths associated with the new flu strain Friday and ordered the most sweeping shutdown of public gathering places in decades.
Authorities closed schools, museums, libraries and theaters in the capital, Mexico City, to try to contain any possible outbreak. Many people in the capital were wearing face masks while in public. Authorities say 1,000 people have become ill.
Mexico's health minister, Jose Angel Cordoba, says the new influenza mutated from pigs to humans and is now considered a "respiratory outbreak." This, he says, is why the Health Ministry in Mexico City is recommending that people avoid crowded places.
Officials at the U.S. Centers for Disease Control and Prevention describe the virus as having a unique combination of genetic material from pigs, birds and humans. They say the virus may be completely new, or may have been present for some time, and only now been detected through improved testing and surveillance.
The CDC says tests indicate some of the Mexico victims died from the same new strain of virus that sickened eight people in California and Texas. But authorities say the U.S. cases have been mild and that all eight people recovered. They say none of the U.S. patients had any contact with pigs.
Dr. Michael Osterholm of the University of Minnesota says while new details about the virus are being learned experts are still not sure how much it might spread. "We are really in a very difficult position right now. We have much more uncertainty than we do certainty and unfortunately that uncertainty all bodes poorly for the future if we show ongoing transmission," said Dr. Osterholm.
Scientists have long been concerned that a new flu virus could spark a worldwide pandemic. A pandemic is usually declared when there is a new virus to which few people have resistance, the virus is easily transmissible and sustainable within a population, and causes severe illness.
The World Health Organization says it has sent a team of experts to the United States and Mexico to monitor the situations there. The WHO says it is convening an expert panel to consider raising the pandemic alert level.
Dr. Richard Besser, acting director of the U.S. Centers for Disease Control, says such a declaration is not likely.
"WHO is not at the point of declaring a pandemic. We are at the point of trying to learn more about this virus and understand its transmission and how to control it," he said.
The CDC says swine flu usually occurs in people who have been exposed to pigs, although human-to-human transmission is also possible. Symptoms resemble the regular human seasonal influenza and include fever, lethargy, lack of appetite and coughing. Its Web site says some people with swine flu experience a runny nose, sore throat, nausea, vomiting and diarrhea.
The CDC also says that between December 2005 and February of this year, 12 cases of human swine flu infection were reported.
U.S. officials say the White House is monitoring the situation.