How do I know if I have a cold or the flu?

Influenza (flu) and a cold are both respiratory (breathing) infections caused by viruses. Some of the symptoms are similar, and it can sometimes be difficult to tell if you have the flu or a very bad cold. The flu can cause more serious illness than a common cold. Your best protection against the flu is an annual flu shot.

You can decrease your chances of getting a cold by frequently washing your hands and avoiding touching your nose, eyes and mouth. The average adults gets one to three respiratory (breathing) illnesses each year, and children get even more. However, it would be unusual to get flu more than once a year.

Sometimes you can get a bacterial infection of the middle ear or sinuses at the same time or following a cold or the flu. These bacterial infections can be treated with antibiotics. The flu, however, can lead to more serious complications such as pneumonia and sometimes death. People who have the greatest risk of severe complications from flu are those 65 years old or older and those with certain medical conditions.

Colds usually begin slowly, two to three days after infection by the virus and normally last only two to seven days. A bad cold can last up to two weeks, but this is unusual. You will first notice a scratchy, sore throat, followed by sneezing and a runny nose. You may get a mild cough several days later. Adults and older children usually don't have a fever, but if they do, it will be very mild. Infants and young children, however, sometimes run temperatures up to 102° F (39° C).

If you have the flu, you will have a sudden headache, dry cough and you might have a runny nose and a sore throat. Your muscles will ache, you will be very tired, and you can have a fever up to 104° F (40° C). Most people feel better in a couple of days, but the tiredness and cough can last two weeks or longer.

The flu is a respiratory (breathing) illness. You cannot have a "stomach flu." Symptoms such as nausea, diarrhea and vomiting are uncommon with the flu, except in very young children. Check with your health care provider if you have questions about the diagnosis and treatment of these illnesses.

The following chart compares the symptoms of the common cold and the symptoms of the flu.
Fever Rare in adults and older children, but can be as high as 102° F in infants and small children. Usually 102° F, but can go as high as 104° F and usually lasts 3-4 days.
Headache rare sudden onset and can be severe
Muscle aches mild usual, and often severe
Tiredness and weakness mild can last 2 weeks or more
Extreme exhaustion never sudden onset and can be severe
Runny nose often sometimes
Sneezing often sometimes
Sore throat often sometimes
Cough mild, hacking cough usual, and can become severe

Last updated: March 2002

Source: Centers for Disease Control and Prevention