How Do You Catch a Cold or the Flu?

woman sneezing

At the first sign of a cold or flu, you may wonder how it happened -- especially if you've taken steps to avoid germs. Here's exactly how you get sick, and what you need to know to protect yourself next time.

  • Viruses spread through tiny droplets in the air that are released when a sick person sneezes, coughs, or blows their nose.
  • You can get sick if you touch your nose, eyes, or mouth after you have touched something contaminated by the virus, such as a toy, countertop, or doorknob. Viruses can live on those objects for up to 2 days.
  • If you come in contact with cold or flu germs, your chance of getting sick isn’t 100%. It depends on when the other person was infected, and how many viral particles are contained in the droplets.
  • People are most contagious during the first 2 to 3 days of a cold. A cold is most often not contagious after the first week.
  • People who have the flu may pass it on to others 1 day before symptoms start and up to 5 to 7 days after getting sick, so they may spread the flu before they even know they are sick.
WebMD Feature Reviewed by Hansa D. Bhargava, MD on January 20, 2017


Charles Gerba, PhD, University of Arizona Mel & Enid Zuckerman College of Public Health.


National Institutes of Health.

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