Common Cold

Common Cold

Cold, Common, acute infectious disease of the upper respiratory tract, caused by more than 100 kinds of viruses. The infection affects the mucous membranes of the nose and throat, causing such symptoms as nasal congestion and discharge, sore throat, and coughing. These symptoms are typical also of respiratory infections caused by bacteria, and of allergic conditions such as hay fever and asthma; therefore, the common cold is difficult to diagnose with certainty.

Normally it runs a mild course, without fever, and subsides spontaneously in about seven days. Its medical significance lies in the possible complications that may ensue. Various diseases, such as bronchitis, pneumonia, and sinus or middle-ear infections, may arise from the cold. Research indicates that there are several strains of each type of virus with varying degrees of virulence. Infection with one strain confers only a brief immunity to reinfection by the same strain, and gives no immunity against the other strains. In 1985, United States researchers using advanced X-ray crystallography techniques produced a three-dimensional, atomic scale model of one of the most common cold viruses. Study of the antibody binding sites on the viral coat revealed a very high degree of antigenic variability, suggesting that production of a vaccine to protect people from the common cold may never be practical.
The common cold was formerly thought to result from exposure to cold weather, a belief probably traceable to the fact that people tend to crowd together indoors at this time, causing a more efficient transmission of virus from person to person. Chilling, also believed to cause a cold, may contribute to infection but some studies suggest that it is not of major importance.

No cure is known for the common cold and no preventive drug has yet been found. In the early 1950s, various antihistamine drugs were claimed to be effective in the prevention of colds if taken at the onset. Most physicians believe, however, that such drugs cannot affect the progress of the true, virus-caused cold. The American chemist and Nobel laureate Linus Pauling proposed that large doses of vitamin C can shorten the duration of a cold and alleviate its symptoms, but several studies have failed to substantiate his claim. Present-day methods of treating a cold are directed toward the relief of symptoms and the prevention of complications. Bed rest is commonly recommended to avoid complications, even when the cold itself is not incapacitating. Antibiotics are often administered as a preventive measure, but there is no evidence that they are helpful.

According to recent statistics, the common cold is the primary cause of absenteeism in schools and industry. In the United States, where individuals have an estimated average of two and a half colds each year, the labor force loses more than 150 million workdays annually. See also Influenza; Virus.