Fast-spreading flu may have infected millions

While the H1N1 pandemic is highlighting both the progress seen in developing new vaccines as well as the opportunities ahead for developers with new technology to offer, it's also providing epidemiologists with a real-world look into how viruses spread.

Researchers at Harvard and the CDC have been using modeling programs to try and determine how many people are actually getting the new flu, which is typically mild and only occasionally lethal. Based on the sharp spike in new cases being handled by physicians, the researchers estimate that there are 70 instances of the flu for every one that winds up reported to officials. And based on those figures, up to 5.7 million Americans contracted swine flu in the first wave earlier this year.

"Relying on laboratory-confirmed cases limits the ability to understand the full impact and severity of the epidemic, especially when severe cases are more likely to be recognized," Carrie Reed and colleagues at the CDC and Harvard wrote. "Health systems and infrastructure may be unprepared in the short-term if plans are based on a number of confirmed cases."

- read the story from Bloomberg