This year's flu season remains unpredictable amid bird flu fears and pandemic worries
Concerns over the seasonal flu, which sickens millions of people each winter, have taken a back seat this year to fears of the bird flu and the horrifying potential that it could evolve into a worldwide pandemic.
The seasonal flu kills about 36,000 people every year and sends 200,000 to the hospital, according to the U.S. Centers for Disease Control and Prevention. But most of those cases involve people who are elderly, very young or weakened by another condition.
For most sufferers -- between 5 and 20 percent of the population every year -- the flu brings fever, headaches, fatigue, aches and pains, stomach distress and other symptoms that make life miserable for days.
A pandemic flu outbreak would be an entirely different problem.
The flu virus mutates frequently and sometimes a new strain emerges that humans have not been exposed to. If the strain spreads easily between humans, it can cause widespread death and overwhelm global health resources.
Health officials stress that there is no evidence of a pandemic flu outbreak anywhere in the world, but say that the avian flu that has spread across Asia and Europe is a cause for concern.