How Cold Virus Infection Occurs
A cold virus is deposited into the front of the nasal passages by contaminated fingers or by droplets from coughs and sneezes. (7) Small doses of virus (1-30 particles) are sufficient to produce infection. (8, 9)
The virus then attaches to a receptor (ICAM-1) which is located on the surface of nasal cells. (11) The receptor fits into a docking port on the surface of the virus. Large amounts of virus receptor are present on cells of the adenoid. (12)
After attachment to the receptor, virus is taken into the cell where it starts an infection. (5) New virus particles are produced in the infected cell. The infected cell eventually dies and ruptures, releasing newly made cold virus to infect other cells in the nose and start the process over again. The virus is much smaller than the cell.
From the time a cold virus enters the nose, it takes 8-12 hours for the viral reproductive cycle to be completed and for new cold virus to be released in nasal secretions. (13) This interval is called the incubation period.
Cold symptoms can also begin shortly after virus is first produced in the nose (10-12 hours). (13) The time from the beginning of the infection to the peak of symptoms is typically 36-72 hours. (1, 2)