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Do I Have the Flu?

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Updated October 28, 2011

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Do I Have the Flu?

Could you have the flu?

Photo © George Doyle/Getty

Figuring out if you have the flu can be difficult. So many flu symptoms are similar to the symptoms of many other common illnesses. If you are feeling sick and want to know if you have the flu, you have come to the right place.

How It Starts

You wake up one morning and suddenly feel like you were hit by a truck. Sore muscles, no energy, and a cough that appears out of nowhere. You think to yourself, "Do I have the flu?" If this scenario sounds familiar, chances are good that you may indeed have the flu.

The flu almost always comes on suddenly. If you have had mild symptoms for a few days that seem to be getting gradually worse, you may have a cold or another viral infection, but it probably is not the flu.

Common Flu Symptoms

If your most significant symptoms are vomiting and diarrhea -- you probably don't have the flu. You may have gastroenteritis (often called the "stomach flu"), but not influenza. Vomiting and diarrhea are actually pretty rare with influenza.

Common flu symptoms include:

  • Fever and Chills
  • Fatigue/Exhaustion
  • Body Aches/Sore Muscles
  • Cough
  • Congestion
  • Headache

Not everyone who gets the flu will experience all of these symptoms, and some of them may be worse for some people than for others. But if your symptoms are significantly different, chances are you don't have the flu.

What if I Got a Flu Shot?

Many people get frustrated when they get a flu shot but then still get the flu (or something like the flu). This frustration is completely understandable, but there are probably several reasonable explanations for why you got sick.

The flu vaccine takes two weeks to be effective.
If you get your flu shot and get sick with the flu a week later, the vaccine has not had enough time to be effective. When this happens, many people are quick to blame the vaccine for actually causing the flu, but that's not likely either. Chances are you picked up the influenza virus around the time you got your vaccine or shortly thereafter. The virus typically incubates for a few days (which means it is living in your body but hasn't caused any symptoms yet) before it makes you sick.

The flu vaccine didn't work for you.
Unfortunately, some people don't respond well to the flu vaccine and end up getting the flu anyway. However, research has shown that when a person gets who has been vaccinated gets the flu, the symptoms are typically more mild and the illness is less serious. They are also less likely to suffer from complications of the flu.

The influenza virus that is making you sick wasn't in the vaccine.
Researchers have to make their best guess about which influenza virus will be circulating during flu season because the vaccine takes about six months to produce. That means that they have to start making the vaccine for the following flu season pretty much as soon as this year's flu season ends. Because the influenza virus mutates and changes so frequently, they don't always get it right. Sometimes the particular strain of influenza that goes around making us all sick wasn't included in the flu vaccine. When this happens, you may get the flu even if you got the vaccine. But like the previous scenario, even when this occurs, research has shown you will probably be less sick than you would have been had you not been vaccinated.

You have a "flu-like illness", but not influenza.
Getting a flu vaccine will usually protect you from influenza, but that doesn't mean you won't get sick for the next six months. There are many other viruses that circulate during flu season (year-round, really) and cause symptoms that are similar to those of the flu. If you have symptoms that are similar to those of the flu, but your health care provider tells you that you don't have influenza, she may diagnose you with a "flu-like illness". Unfortunately, the flu vaccine doesn't protect us from these viruses. Luckily, even though they may make you feel terrible, they usually aren't as serious or as likely to lead to serious complication as the actual influenza virus.

Still Not Sure if You Have the Flu?

If you still can't figure out whether or not you have the flu, take our quiz and then contact your health care provider. She can test you for the flu, diagnose you appropriately and even prescribe antiviral medications if you need them.

Source:

"Influenza Symptoms." Seasonal Influenza (Flu) 30 Sep 10. US Centers for Disease Control and Prevention. 22 Oct 11.

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