The common cold, also known as a viral upper respiratory tract infection, is a contagious illness that can be caused by a number of different virus types. Because of the variety of viruses involved, the body is never able to build up resistance against all of them. For this reason, colds are a frequent and recurring problem, with symptoms ranging from sneezing and coughing to nasal congestion and a sore throat.

Fortunately, you can help protect yourself by washing your hands frequently and avoiding prolonged contact with those who are sick. Here, a look at colds by the numbers.

  • Approximately 1 billion: Total number of colds Americans suffer from each year.

  • 6 to 10: Approximate number of colds the average child suffers from each year, according to the National Institutes of Health.

  • 22 million: Number of school days lost annually in the U.S. due to the common cold, according to the Centers for Disease Control and Prevention (CDC).

  • 30 to 35: Percentage of adult colds that are caused by the rhinovirus, the most highly contagious of all the cold viruses.

  • Up to 12: Number of feet that virus particles can travel.

  • Up to 3. Number of hours a rhinovirus can survive outside the nasal passages on inanimate objects and skin.

  • 2 to 3: Number of days after infection with a cold virus that symptoms generally begin.

  • 2 to 4: Number of days after symptoms first appear that a cold is most contagious.

  • 1 to 2: Typical number of weeks a cold lasts.