Centers for Disease Control and Prevention
Centers for Disease Control: Influenza: The Disease
Find a list of "flu-like symptoms," learn who is at risk for developing the flu, and read about how the flu is spread. This website also provides a chart showing "peak months for flu activity" and advice for treating the flu and flu...
US Food and Drug Administration
Fda: Influenza Virus Vaccine Safety & Availability
The FDA provides a brief description of flu symptoms, an overview of the high-risk groups that ought to get yearly flu vaccines, and links to articles and statistics on flu vaccines from the year 2000 to now.