Epidemiologists puzzled by swine flu's impact

As a bevy of vaccine makers around the world rush into the clinic with new swine flu vaccines, epidemiologists are still puzzling out how the new flu works and why many young people without any health complications are often hit the hardest by H1N1.

In Canada, where a third of the population is expected to be affected, two out of three confirmed flu patients have no underlying health conditions. And in Mexico physicians concluded that it was the 20-to-50 age group that was most threatened. In most cases, the flu is somewhat more serious than seasonal flu, but still quite mild. What the specialists can't determine is why some people are killed by it.

"They are ending up on ventilators and it can last from weeks to months," Michael Gardam, director of infectious diseases at the Ontario Agency for Health Protection and Promotion, tells the Globe and Mail. "I would like people to be concerned about H1N1, without panicking. More concerned than they are about seasonal flu."

- read the report from the Globe and Mail

ALSO: In the U.S., health officials expect to have 50 million doses of vaccine on hand by October 15, with millions of additional doses in hand later in the season. Report

PLUS: Both China and the UK have now stopped trying to contain the pandemic and have switched strategies, focusing on individual patients. Report