The incidence of a cold varies with the time of the year, having three peaks in autumn, winter and early spring. The PAGB survey shows that 15 per cent of adults had a cold in the last two weeks, which may be compared to the 27 per cent of children under 15 years old. Pathophysiology Coryza is an upper respiratory tract infection caused by a virus. Over 200 viruses, including rhinoviruses, coronoviruses, adenoviruses, echo viruses, parainfluenza viruses 1-4 have been shown to cause the common cold. The first two listed account for about 50-60 per cent of all attacks.
Cold viruses enter the body through the nasal mucus membranes.
Following penetration, they shed their coat, release their nucleic acid and replicate. As the virus spreads, the body produces an inflammatory reaction in target organs. The cold viruses target organ is the respiratory epithelium. The major target organ is specific for each virus. This accounts for the different types and sequences of symptoms that each cold attack displays.