The common cold is a benign self-limited syndrome representing a group of diseases caused by members of several families of viruses. It is the most frequent acute illness in the United States and throughout the industrialized world . The term "common cold" refers to a mild upper respiratory viral illness involving, to variable degrees, sneezing, nasal congestion and discharge (rhinorrhea), sore throat, cough, low grade fever, headache, and malaise. The common cold is a separate and distinctly different entity than influenza, pharyngitis, acute bronchitis, acute bacterial rhinosinusitis, allergic rhinitis, and pertussis.
The common cold is associated with an enormous economic burden as assessed by lost productivity and expenditures for treatment . A US telephone survey conducted between 2000 and 2001 indicates that about 500 million non-influenza viral respiratory infections occur yearly, resulting in estimated direct costs of $17 billion and indirect costs of $22.5 billion annually .
The average incidence of the common cold is five to seven episodes per year in preschool children, and two to three per year by adulthood . Annual absences from school and work in the United States due to colds caused 26 and 23 million lost days, respectively . Colds account for 40 percent of all time lost from jobs among employed people . It is no surprise then, that tens of millions of research dollars have been spent on ways to prevent and shorten the course of the common cold. (See "The common cold in children: Clinical features and diagnosis" and "The common cold in children: Treatment and prevention".)
The epidemiology and clinical manifestations of the common cold are discussed here. Treatment and prevention of colds are discussed separately. (See "The common cold in adults: Treatment and prevention".)
Over 200 subtypes of viruses have been associated with the common cold. New viruses, such as the human metapneumovirus and bocaviruses, have been identified using PCR and Virochip technology, and it is anticipated that additional viruses that also cause the common cold are yet to be identified.