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The Life Cycle of a Common Cold

The common cold is a self-limited viral infection of the upper respiratory tract that almost always runs the same course. The incubation period lasts about 24 to 72 hours. A tickly nose, the urge to sneeze, and a scratchy throat are usually the first tangible signs.

If the immune system does not manage to fend off the viruses at this stage, it is not long (typically one to three days) before the tickle intensifies and the scratchiness becomes a sore throat. There is often an urge to cough, which can lead to painful fits of coughing. Fever is rare in adult cold sufferers, but is frequent in children. After one to three days, the discharge in the bronchial tubes and nose becomes thick and the dry cough becomes productive. The typical cold takes an average of seven to 10 days—and in some cases up to three weeks—to wear off completely. The cough is often persistent and may last longer than other symptoms.1

After recovering from the cold, the immune system builds up antibodies to defend itself from catching that particular cold virus again. However, given that there are more than 200 strains of cold viruses, the immune system is still susceptible to other strains.


The Life Cycle of the Typical Cold


The Role of the Immune System

The human body's immune system is extremely complex, and is not yet fully understood by scientists. The main function of the immune system is to defend the body against foreign substances, including viruses, bacteria, and fungi. Various organs and cells are involved in combating the infiltrators—and the enemies within— including the bone marrow, lymph nodes and tissue of the respiratory tract, the digestive tract, the lungs, and the urinary tract, as well as the spleen, liver, and thymus gland.2


1 Heikkinen, T, Jarvinen, A, The common cold, The Lancet, 4 January 2003; 361: 51-58.16.
2 Schindler, LW, Understanding the Immune System, Diane Publishing, 1991: 3-4.