Text VI. The Common Cold

Common colds, like other virus infections of the respiratory tract, have so far eluded all attempts at their control; neither vaccines nor drugs have as yet made any significant impact on the very successful causal parasites. However, since the first common cold viruses were cultivated approximately 20 years ago, research has produced a great deal of knowledge about the viruses themselves and their epidemiological and pathological potentialities, and there is now a firm base from which attempts to prevent or treat these infections can be directed.

The clinical features of an uncomplicated common cold are well known. The incubation period lasts about two days and is followed by a nasal obstruction, rhinorrhoea, sneezing, “scratchiness” or soreness of the nasopharynx, cough and sometimes hoarseness, lasting up to a week. Fever or other constitutional symptoms and lower respiratory symptoms are unusual. The syndrome has been shown to result from acute infection of the epithelial cells of the upper respiratory tract, for which common cold viruses have a specific tropism. The epithelial cells are destroyed as the viruses multiply in them, with consequent mechanical damage to the mucociliary transport mechanism. To this is added inflammatory reaction, edema and excessive secretion.

Infectious rhinitis, the common cold, is due to a variety of viruses, although two groups, the rhinoviruses and the coronaviruses, are of major importance. However, other respiratory viruses which are capable of producing more severe illness, particularly in children, may also sometimes cause symptoms of the common cold.

These include influenza viruses and adenoviruses. For common colds in adults, a present estimate is 40 to 50% due to rhinoviruses and 15 to 20% due to coronaviruses.

Infections occur all year round, but there is a peak of prevalence in autumn and often another in spring. More than one virus type may be present at the same time within a family, and within larger communities, such as students, many types will be circulating concurrently and the prevalent types will vary from year to year. Attempts have been made in order to determine whether any particular serological types are consistently common in different geographical areas. This is unfortunately not so; if it were vaccination might produce an overall effect on the incidence of colds.

24. Read text VII and say what one should do to avoid colds: