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Why is outbreak hitting Mexico harder?

By Rita Rubin, USA TODAY, April 27, 2009

So far, only Mexico has reported deaths of people with laboratory-confirmed swine flu, but the disease isn't necessarily more severe in that country than elsewhere, U.S. scientists said Monday.

"There's so much unknown at this point," notes Joan Nichols of the University of Texas Medical Branch at Galveston's Center for Biodefense and Emerging Infectious Diseases.

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The Associated Press quotes Mexico's health secretary saying the country confirmed 20 deaths linked to swine flu. (The World Health Organization puts lab-confirmed deaths at seven.) The USA has had 40 confirmed cases and no deaths.

But Mexico is reporting nearly 2,000 suspected cases and, AP says, up to 149 suspected deaths. Perhaps swine flu seems to be more lethal there because it has cut a wider swath, says William Schaffner, infectious-diseases chair at Vanderbilt University in Nashville. "Until we get more information, we won't be able to put our arms around it," he says.

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In particular, he says, he'd like to know the ages of swine flu victims who died. If they tended to be old, they might have had underlying ailments, such as heart or lung disease, that increased the risk of complications.

"There are always a lot of variables when you talk about transmission of disease," says Dan Hinthorn, director of infectious diseases at the University of Kansas Hospital in Kansas City.

Mexican officials are reporting a swine flu death rate approaching the 8% to 10% death rate from SARS (severe acute respiratory syndrome, which struck Southeast Asia and Canada in 2003), Hinthorn says. But, he speculates, perhaps many more Mexicans actually have had swine flu than health officials realize because their illness was milder and they never saw a doctor. If so, he says, the death rate could be far lower.

Julio Frenk, new dean of the Harvard School of Public Health, served as Mexico's health minister from 2000 to 2006. He talked from Mexico City, where he was visiting family. "I think the epidemiologists here are very, very competent and very committed to timely, transparent reporting," Frenk said, noting that he was speaking as a knowledgeable "external observer." "Obviously, some of the information takes time."

For now, he says, Mexican officials' top priority is to contain the swine flu outbreak and take care of people who are sick. Whether it is causing more severe disease in Mexico than elsewhere "needs to be answered through research," Frenk says.

Initial numbers show that previously healthy people ages 25-45 make up the largest number of reported Mexican swine flu cases, he says roughly the same age group hardest hit in the 1918 flu pandemic.

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