Swine Flu on Track to Be a Pandemic

New analysis says H1N1 flu's spread is similar to that in big 20th-century pandemics.

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Swine flu spreads easily enough and infects enough people to spark a global pandemic, according to a new analysis by the World Health Organization’s Rapid Pandemic Assessment Collaboration. That’s the news of the day, released early by the journal Science “because it contains important public health information.” The bottom line: We’re not safe yet, despite the Monday-morning feeling that swine flu is last week’s news. This may be just the first weeks of a three-to-five-year pandemic, with wave after wave of sickness and death.

It’s still impossible to tell how bad H1N1 is going to be, the WHO team says. But by looking back at how many cases there have been in Mexico (many more than the 4,694 confirmed cases listed by WHO) and by tracking the virus’s spread through international travel, the WHO researchers were able to get a better sense of how dangerous this bug is. Here are the key numbers:

  • About 23,000 people fell ill in Mexico by April 30, the scientists estimate, giving the outbreak a death rate of between 0.3 and 1.5 percent, about the same as in the 1957 global flu pandemic. By comparison, the death rate in the 1918 flu pandemic was about 2.5 percent. Mexican health officials said the two groups most likely to die were previously healthy young people who deteriorated rapidly with acute pneumonia and people with chronic health conditions such as cardiovascular disease or tuberculosis.
    • Children were twice as likely as adults to fall ill with swine flu, with 61 percent of children under age 15 infected in La Gloria, Mexico, the village where the outbreak was discovered. Just 29 percent of residents over age 15 got sick. Those numbers are comparable to or higher than those seen in previous flu pandemics.
      • This virus causes 1.4 to 1.6 new cases of flu from each infected person, on average, which is similar to or lower than the pandemics of 1918, 1957, and 1968.
      • These numbers mean that swine flu/H1N1 is acting like a pandemic flu, and that we should act as if it’s a pandemic, too. There’s still not enough good information to know if it makes sense to close schools or use other social-distancing measures to save lives, say the WHO researchers. But this latest analysis supports the argument of WHO Director-General Margaret Chan and other global health experts that we should be getting ready for more trouble. An article on swine flu in last week’s New England Journal of Medicine pointed out that in the three 20th-century pandemics, multiple waves of outbreaks caused increased numbers of deaths for three to five years.

        The federal Centers for Disease Control and Prevention has estimated that a medium-level pandemic in the United States could kill 89,000 to 207,000 people and affect 15 to 35 percent of the population. By contrast, the CDC estimates that regular seasonal flu kills about 36,000 people a year, most of them elderly.

        Don’t throw out the hand sanitizer; we’re in this for the long haul.

        Resources: Earlier I wrote about the CDC’s new game plan for flu-related school closures. A risk-management expert gave good advice on how to help your family manage swine flu fears. And Ted Epperly, the president of the American Academy of Family Physicians, told me how to stockpile food and medical supplies for a pandemic.