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How Contagious is the Cold or Flu?

By Caroline Pak, PharmD, Medical Editor-in-Chief - This article originally published on Get Healthy Stay Healthy.

If a family member or coworker has the sniffles, do you avoid them as best you can? If someone standing behind you at the grocery store blasts the back of your head with a hack-hack-cough-sneeze combination, do you feel like you want to duck and run to avoid getting sick? Some people might not worry about catching whatever those sniffly sneezing people have, but should they?

If you are concerned about catching colds or the flu during the winter months, it might help to know a few things about the common cold or flu.

Cold vs. Flu—What’s the Difference?

The common cold is not the same thing as the flu, and vice versa. Both cold and flu are infections that can cause symptoms in the respiratory system (nose, throat, and lungs), but different viruses cause them. Only influenza viruses cause the flu, while many different types of viruses (e.g., rhinovirus, adenovirus) can cause colds. Antibiotics do not work for cold or flu, but there are antiviral medications that can be used to treat the flu.

Symptoms of the cold and flu may be so similar that it’s sometimes hard to tell them apart. However, in general, the flu causes more intense symptoms than the common cold. The flu usually lasts longer (from several days to less than two weeks) and is more severe. Flu is also more likely than a cold to lead to more serious illnesses, such as pneumonia.

There are some other differences, too. For instance, cold symptoms usually include a runny or stuffy nose, scratchy or sore throat, cough, headaches, and body aches. The flu can cause these symptoms too, but they are much more severe. The flu can also cause fever and chills—adults with colds usually have no fever or low fever.

To check out some more differences between the cold and flu, read more about it here.

How Can You Catch the Cold or Flu?

Most cold and flu viruses are passed from person to person through tiny respiratory droplets that are sent through the air when people cough, sneeze or talk. These droplets can land in your mouth or nose, and be inhaled into your lungs. According to the Centers for Disease Control and Prevention (CDC), the flu virus can be transmitted via air particles to another person who is standing up to about 6 feet away.

It may also be possible to get the flu or cold by touching a surface or object that has the virus on it, then touching your eyes, mouth or nose.

Most of us may know that you can pass the flu virus to others while you are still sick. But did you know that you can also spread the flu to someone before you even know you are sick? Healthy adults may be able to infect other people 1 day before symptoms develop and up to 5 to 7 days after first becoming sick. Children may be able to pass the flu virus for longer than 7 days.

People who have the common cold are most contagious for the first 2 to 3 days of a cold. A cold is most often not contagious after the first week.

How Can You Prevent Catching the Flu or Cold?

Here are few things you can do to help reduce the spread of cold or flu viruses:

  • Stay home when sick. Remember you can infect others with viruses that cause the common cold for up to 2 to 3 days after getting sick, and with the flu for up to one week after getting sick
  • Avoid contact with others who are sick. Avoid bodily contact such as kissing or shaking hands. If you do shake hands with someone who is sick, avoid touching your mouth or nose until you can thoroughly wash your hands
  • Wash hands often. Especially after coughing, sneezing and blowing your nose
  • Disinfect frequently touched surfaces, like doorknobs or light switches
  • Cover your coughs and sneezes. Use a tissue (then throw it away) or use your elbow to stop those virus particles from going airborne
  • Get the flu shot every year, if appropriate for you. Keep in mind that there’s no vaccine for the common cold.

Caroline Pak, PharmD, is a pharmacist and the Medical Editor-in-Chief for Pfizer’s Get Healthy Stay Healthy website.