Adults average about two to four colds a year, although the range varies widely.
On average, individuals older than 60 have fewer than one cold a year. Colds are most prevalent among children, and seem to be related to youngsters' relative lack of resistance to infection and to contacts with other children in day-care centers and schools. More than 200 different viruses are known to cause the symptoms of the common cold. Coronaviruses are believed to cause a large percentage of all adult colds. They induce colds primarily in the winter and early spring.