Newswise — “My body aches and my head is throbbing. Do I have the flu or is it just because I’m stressed or tired? Do I need a flu shot? Do I need the H1N1 vaccine, too?”

Millions of Americans will be asking themselves these and more questions this fall and winter as news reports and health care providers continue to warn about seasonal influenza and novel H1N1 influenza, otherwise known as swine flu.

The flu symptoms self-assessment tool on MayoClinic.com helps you assess whether you or your loved ones have some form of flu, or just a cold. If you possibly or likely have the flu, you’ll also learn whether antiviral medication is an option. And you can check a concise list of high-risk groups who should seek medical attention for the flu.

Influenza is a viral infection that attacks the respiratory system, including the nose, throat, bronchial tubes and lungs. If you’re generally healthy and you catch influenza — commonly called the flu — you’re likely to feel rotten for a few days, but you probably won’t develop complications or need hospital care. If you have a weakened immune system or chronic illness though, influenza can be fatal.

Novel H1N1 flu, popularly known as swine flu, is a respiratory infection caused by an influenza virus first recognized in spring 2009. The new virus, which is officially called swine influenza A (H1N1), contains genetic material from human, swine and avian flu viruses. Unlike typical swine flu, H1N1 flu spreads quickly and easily.

Based on the expertise of Mayo Clinic infectious disease and epidemiology scientists and physicians, and other specialists for specific populations such as children or pregnant women, MayoClinic.com provides continually-updated and credible information regarding the seasonal flu and H1N1 flu vaccines and treatment recommendations.

About MayoClinic.comSince 1904, millions of people from all walks of life have found answers at Mayo Clinic. Now, when people need answers they can trust, they can also visit MayoClinic.com. Launched in 1995 and visited by millions each month, this award-winning Web site offers health information to help users assess symptoms, understand their diagnosis and manage their health. Produced by a team of Mayo Clinic experts, MayoClinic.com gives users access to the expertise and knowledge of the more than 3,300 physicians and scientists of Mayo Clinic. The Web site offers more ways to get information — search by symptom, procedure, disease or condition, with convenient tabs on every page for quick links to comprehensive resources about specific health conditions. Backed by the expertise of Mayo Clinic, MayoClinic.com provides the peace of mind that results from knowing its medical information comes from some of the world's leading experts. Users can sign up for a free weekly e-newsletter, “Housecall,” which includes the latest health information from Mayo Clinic. For more information, visit http://www.mayoclinic.com/.