The viruses

The main viruses associated with the common cold are rhinoviruses (over 100 types), coronaviruses, influenza viruses, respiratory syncytial virus and parainfluenza viruses.

Epidemiology

Route of spread

The mechanism of transmission of the common cold is different for different viruses. There are three main routes of transmission – direct contact (the virus is transmitted by skin contact from handling an infected object and transmission to the mouth or nose), via small particle aerosols (these hang around in the air and can be highly infectious) and/or via large particle aerosols (created by coughing and sneezing).

Prevalence

As its name suggests, the common cold occurs throughout the year. It is most prevalent in children, especially in younger children. Pre-school or primary school children have about 3–8 colds a year, whereas adults usually have 2–4 colds per year. Parents, teachers and others in frequent contact with young children have more colds than those with minimal contact. Women have more colds than men, probably reflecting their increased contact with children.

The common cold is more prevalent in winter months (usually caused by rhinoviruses or parainfluenza types 1 and 2 virus). Summer colds are more likely to be caused by coronaviruses or parainfluenza virus type 3. Quite why parainfluenza viruses type 1 and 2 cause winter infections and parainfluenza virus type 3 causes summer infections is a mystery! It is a myth that colds are more likely to be acquired in cold and wet weather.