THE COMMON COLD

The common cold has intrigued physicians and the general public for centuries. It has been defined as an acute epidemic respiratory disease characterized by mild coryzal symptoms of rhinorrhea, nasal obstruction, and sneezing. The nasal discharge is usually copious and thin during the first 2 days of illness, then it generally becomes more viscous and purulent.(22) The disease is self-limited. Symptoms may persist for 2 days to more than 14 days; however, the cold may abort after only 1 day. Fever, cough, sore throat, or lacrimation may or may not be present. The common cold is of itself harmless, but bacterial invasion frequently follows the initial infection. It is these secondary invaders that may produce disorders of serious consequence. The common cold is the most frequent acute illness in the United States and throughout the industrialized world. About half the population gets at least one cold every year.(5) Colds account for 40% of all time lost from jobs among employed people (23 million days of work per year) and about 30% of absenteeism from schools (26 million school days per year). Estimates vary, but the average preschool child has somewhere between 4 and 10 colds per year, and the average adult has about two to four colds per year. The actual cost of caring for patients with colds in US physicians' offices is estimated to be $1.5 billion annually.(64) Seasonal patterns of infection can be identified for some of the various types of viruses that are responsible for outbreaks of the common cold. For example, available epidemiologic data suggest early fall and late spring are the most common times to find more outbreaks of rhinovirus. Respiratory syncytial virus (RSV) tends to follow winter and spring incidence, with a peak number of cases found mainly in January. Parainfluenza types 1 and 2 seem to peak during the autumn, whereas parainfluenza type 3 has an increased incidence during the late spring. Adenoviruses and coronaviruses tend to produce epidemics during the winter and spring (Fig. 1) This article presents data concerning the cause, pathogenesis, and treatment of the common cold, as well as discussion of the available diagnostic tests and their use in formulating differential diagnoses.