Colds are caused by more than 200 different viruses known as rhinoviruses. They are not caused by the same viruses responsible for influenza ("the flu"). Colds spread through exposure to droplets from the coughing or sneezing of others with a cold or by hand contact with objects contaminated by someone with a cold.
The incidence of colds is highest among children, and the incidence decreases with age because immunity to the virus causing the cold occurs after the illness. Gradually, immunity to a wide variety of viruses that cause colds is developed in adults. On average, children have 10 colds a year and adults have 3.
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