Like the flu, a cold is caused by a virus, but thankfully, it’s much less threatening than the influenza virus. Like other viruses, it invades the body through the nose or mouth, either by inhaling tiny particles in the air from an infected person’s cough or sneeze, or by touching your mouth or nose after contact with a contaminated surface or object.
Once the virus invades, you have an infection of the upper respiratory tract, including your nose, sinuses, and throat. Cold symptoms are caused not by the virus itself, but by the immune response in the upper respiratory tract as it tries to fight off the virus, causing acute inflammation.
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