Diseases of the Respiratory System - The common cold, influenza, and other viral infections

The Common Cold

The common cold is the most prevalent illness known to mankind. It accounts for more time lost from work than any other single condition. The infection rate varies from one individual to another.

Surveys indicate that about 25 percent of the population experience four or more infections a year, 50 percent experience two or three a year, and the remaining 25 percent have one or no infections in a year. There is also some variation from year to year for each person, explained often by the amount of exposure to young children, frequent extreme changes in weather, fatigue, and other factors.

For years it has been felt that chilling plays a role in causing the common cold, and, although difficult to prove, there is almost certainly some truth to the idea. By some as yet unclear process, chilling probably causes certain changes in our respiratory passages that make them susceptible to viruses that otherwise would be harmless.

The common cold affects only the upper respiratory passages: the nose, sinuses, and throat. It sometimes is associated with fever. Several viruses have been implicated as the cause for the common cold. But in the study centers that investigate this illness, isolation of a cold virus is only achieved in about one half of the cases. These viruses are not known to produce any other significant illnesses. Most likely they inhabit the nose and throat, often without producing any illness at all.


The major part of the illness consists of about three days of nasal congestion, possibly a mild sore throat, some sneezing and irritation of the eyes (though not as severe as in hay fever), and a general feeling of ill health often associated with some muscle fatigue and aching. After three days the symptoms abate, but there is usually some degree of nasal congestion for another ten days.

Prevention is difficult, and there is no specific treatment. The natural defenses of the body usually are capable of resolving the infection. Attention should be paid to avoiding further chilling of the body, exhausting activity, and late hours that can further lower the defenses and lead to complications.


Ear infection may develop because of blockage of the Eustachian tube , which leads from the back of the throat to the inner part of the ear. That complication is heralded by pain in the ear. Bronchitis and pneumonia may be recognized early by the development of cough and production of sputum (phlegm). Sinusitis develops when the sinus passages are obstructed so that the infected mucus cannot drain into the pharynx (as in postnasal drip). The pain develops near the sinus cavity involved. These complications can and should be treated with specific drugs, and, if they develop, a physician should be consulted.


A number of other viruses cause respiratory illness similar to the common cold, but are much more severe in intensity and with frequently serious, and even fatal, complications. The best known member of the group is the influenza (flu) virus. It can cause mild symptoms that are indistinguishable from those of the common cold, but in the more easily recognizable form it is ushered in by fever, cough, and what physicians refer to as malaise —chills, muscle ache, and fatigue.

The symptoms of influenza appear quickly; they develop within hours and generally last in severe form from four to seven days. The disease gradually recedes over the following week. The severity of the local respiratory and generalized symptoms usually forces the influenza patient to stay in bed.

Not only is the individual case often severe, but an outbreak of influenza can easily spread to epidemic proportions in whole population groups, closing factories, schools, and hospitals in its wake. There have been 31 very severe pandemics (epidemics that sweep many countries) that have occurred since 1510. The most devastating of these pandemics occurred in 1918; it led to the death of 20 million people around the world. Rarely is death directly attributable to the influenza virus itself, but rather to complicating bacterial pneumonia or to the failure of vital organs previously weakened by chronic disease.

Flu Shots

Inoculation is fairly effective in preventing influenza, but is not long-lasting and has to be renewed each year. Unfortunately, there are several different types of influenza virus, and a slightly different vaccine is needed to provide immunity to each type of infection. Each recent epidemic in the United States has been the result of a different strain, and although there have been several months’ warning before the epidemics started, it has been difficult to mass-produce a vaccine in time to use it before the epidemic developed.


Once acquired, there is no cure for influenza, but the body defenses are usually capable of destroying the virus if given the necessary time and if the defenses are not depressed by other illness. Fluids, aspirin, and bed rest help relieve the symptoms. Special attention should be paid to sudden worsening of fever after seeming recovery, or the onset of sputum production. In elderly people more intensive medical care is often necessary, including hospitalization for some.

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