In 1918, a flu pandemic caused by a strain of H1N1 infected 500 million people worldwide. It was known as the Spanish flu, and at least 50 million people died.

The United States may be headed for a rough flu season, with a virus that causes more severe symptoms than the one last year ...

U.S. officials said Monday that it's too early to say the swine-flu threat is receding, even though there are some signs the outbreak may not be as serious as originally feared. Homeland Security ...