Swine Flu Behavior "Potentially Scarier Than the Outbreak of Avian Flu"

Jon is a staff writer for Science.

The level of worry about a swine flu outbreak in the United States rose a notch today, as health officials linked the virus that has infected eight people here to a strain circulating in Mexico that may have spread to hundreds of people and caused dozens of deaths. “Our concern has grown since yesterday,” said Richard Besser, the acting director of the U.S. Centers for Disease Control and Prevention .

At a press conference today, Bresser said CDC scientists had done a partial genetic analysis of seven isolates from Mexico. “From everything we know to date, the virus appears to be the same,” said Besser. He said CDC also had confirmed one more case in the United States, a child from San Diego, California. All of the other U.S. cases were from people in southern California or San Antonio, Texas, and he said one of them recently had traveled to Mexico. Although both of these locales have large Mexican-American communities that have frequent contacts with Mexican immigrants, he didn't answer a question that directly asked about the ethnicity of the U.S. cases.

Bresser stressed that at the early stages of any outbreak, much uncertainty exists and the CDC’s approach and advice may likely change as the scope of the spread becomes more clear. For now, CDC has not issued any warnings about domestic or international travel, and the pandemic threat level has not been increased. “We do not know whether this virus will lead to next pandemic,” he said.

CDC is working closely with the World Health Organization, and Mexican officials, said Bresser. WHO plans to convene an emergency committee under international health regulations, possibly as soon as tomorrow. Bresser said CDC has yet to send a team of its investigators to Mexico. “We are still in discussions with Mexico, but we anticipate that we will have folks there very soon.”

Swine flu typically moves from pigs to humans, but this strain has caused particular alarm because it appears to transmit directly from one human to another. Two of the U.S. cases were a father and a son, and two others attended the same high school. None of the U.S. cases had any known contact with pigs. “Human-to-human transmission is really scary,” says virologist and influenza expert Douglas Richman of the University of California, San Diego. “It’s potentially scarier than the outbreak of avian flu.”

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