Cold & Flu Health Center
Top 10 Questions About the Flu
Influenza, or flu, is a virus that targets the respiratory system. Find answers to the 10 most common questions about the flu.
1. What is the difference between a cold and the flu?
The flu and the common cold are both respiratory illnesses, but they are caused by different viruses. Because they have similar symptoms, it can be difficult to tell them apart.
Influenza or "the flu" develops when a flu virus infects your respiratory system, including your nose, throat, bronchial tubes, and possibly the lungs. A cold virus usually infects only your upper respiratory tract: your nose and throat. Flu symptoms are generally worse than illness caused by the common cold. What we call "stomach flu" or "intestinal flu" is really another virus that causes vomiting and diarrhea. It's confusing terminology, because it really isn't the flu. It's just another type of viral infection.
2. Why are people so concerned about the flu?
Because the flu virus can infect the lungs, it can cause a serious infection like pneumonia. And that's what worries people. If the flu develops into pneumonia, it can require hospitalization and even lead to death. People with weak immune systems -- the elderly, pregnant women, infants, and people with chronic health problems -- are at highest risk.
3. Can flu shots cause the flu?
The flu shot is made from killed viruses and cannot "give" you the flu. However, the vaccine can trigger an immune response from your body, so you may have a few mild symptoms, like achy muscles or a low fever.
The nasal flu vaccine, FluMist, is made with weakened live virus. It's recommended as an option only for nonpregnant, healthy people between the ages of 2 and 49.
Because flu viruses differ from year to year, you need an annual flu vaccine to try to prevent the flu. The vaccines don't guarantee that you are 100% protected. You could catch a strain that is not included in this year's shot. Recent research also indicates that the vaccine may not be as protective for children under age 2. But flu shots are considered the best prevention available today.
The CDC advises everyone 6 months and older to get a flu vaccine every year.
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