The common cold in adults: Diagnosis and clinical features

INTRODUCTION

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 [1]. 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. It is to be distinguished from influenza, pharyngitis, acute bronchitis, acute bacterial sinusitis, allergic rhinitis, and pertussis.

The common cold is associated with an enormous economic burden both in lost productivity and in expenditures for treatment [2]. A US telephone survey conducted between 2000 to 2001 indicates that about 500 million non-influenza viral respiratory infections occur yearly, resulting in direct costs of $17 billion and indirect costs of $22.5 billion annually [3].

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 due to colds from school and work in the United States caused 26 and 23 million lost days, respectively [2]. Colds account for 40 percent of all time lost from jobs among employed people [1]. (See "The common cold in children".)

It is no surprise then, that considerable research dollars have been spent on ways to prevent and shorten the course of the common cold. 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".)

VIROLOGY

Over 200 subtypes of viruses have been associated with the common cold. New viruses, such as the human metapneumovirus and bocaviruses, have been identified with PCR and Virochip technology, and it is anticipated that additional virus types are yet to be identified.