With all the wonders of modern medicine, it is easy to think of flu epidemics as something from our less medically sophisticated past. For instance in 1918, 20 million people died worldwide from the flu. Though we have not had a pandemic on that order since then, flu typically kills 30,000 Americans annually.
This year's flu season appears to have arrived early and the stain appears to be more dangerous than usual as reported here and here.
For a complete FAQ, check out the CDC web site.
If you haven't got your flu vaccine shot yet, please do if at all possible.