BREATHE EASY

From Colds to Influenza: Common Infections of the Respiratory Tract

WHAT IS THE COMMON COLD?

It is impossible to talk about colds without discussing viruses, since these ubiquitous organisms are the cause. Viruses are submicroscopic living particles, smaller than bacteria, that can infect any part of the body and cause symptoms. The lungs and respiratory tract are particularly vulnerable since viruses are easily passed from person to person in the air.

Viruses can cause virtually any type of respiratory infection. The most benign is the common cold. The most serious is a form of pneumonia caused by influenza virus that can spread to involve both lungs and prove fatal (see Section N). In the United States viral infections of the respiratory tract are responsible for an estimated 250 million lost work days annually. One estimate puts the economic loss at 5 billion dollars each year, of which the common cold accounts for approximately 2 billion dollars. The common cold, bane of millions, is the most frequent viral infection of the respiratory tract. It occurs with characteristic symptoms: some combinations of runny nose, watery eyes, cough, sneezing, mild sore throat, malaise, and headache. Not all symptoms are present every time. Fever may also occur, but is usually low grade. The symptoms run their course in a week or so, and otherwise healthy people recover without any specific treatment.

Each person has, on the average, two to three colds a year. The virus types responsible for most of them are rhinovirus ("rhino" from the Greek word for nose) and coronavirus ("corona" from the halo formed around the virus's body when seen under the electron microscope). Many other virus types may also cause the common cold.

Rhinovirus is transmitted through the air, often as a result of coughs; it may also be spread by sneezing or even during talking. Rhinovirus and other cold viruses can also be contacted from objects (clothes, phones, books, and so forth) where the virus has settled.

WHAT IS THE BEST TREATMENT FOR THE COMMON COLD?

The old adage about bed rest and plenty of fluids for treating the common cold is as true now as a century ago. Aspirin may help to relieve malaise and discomfort and a nasal spray may ease the congestion, but there is simply no specific treatment for the common cold. Fortunately, recovery usually occurs in a few days no matter what we do.

For the uncomplicated cold antibiotics are not helpful; they will not speed recovery. Antibiotics may help the common cold patient who has underlying chronic lung disease and the possibility of a bacterial infection, or who has a complication of the cold such as sinus or ear infection.

It is a good idea not to take antibiotics for the common cold without consulting a physician. You may be taking an antibiotic inappropriately or the wrong antibiotic. Cold symptoms that should alert you to the possible need for medical evaluation include:

IS VITAMIN C HELPFUL?

Vitamin C is ascorbic acid, one of the essential vitamins since it must be supplied in the diet – your body cannot make it. Lack of Vitamin C leads to scurvy, a discovery made in the 1800s when a daily ration of limes was found to prevent the disease in British sailors. True lack of Vitamin C causes malaise, irritability, emotional disturbances, arthralgia (joint pain), nosebleeds, and bleeding under the skin. It is rare for anyone in this country to be truly deficient in Vitamin C, although it can occur in alcoholics, dietary cultists, and some chronically ill patients.

The daily need for Vitamin C at any age is between 35 and 60 milligrams. A glass of orange juice (200 ml) contains 100 mg, so it is not difficult to obtain the daily requirement. Those who recommend Vitamin C for colds and flu advocate megadoses, at least 1,000 mg/day or more. Whether or not this is helpful is problematical. In 1970 Nobel prize­winning scientist Dr. Linus Pauling published a book strongly advocating ascorbic acid for the common cold. Since then there have appeared dozens of scientific articles and statements supporting both sides of the issue. There is no consensus among the medical community about the value of Vitamin C in either preventing or treating colds and flu. This lack of consensus reflects the conflicting nature of the medical findings.

The 1983 edition of AMA DRUG EVALUATIONS makes this statement (page 575): * Since the use of large doses of vitamin C were recommended on theoretical grounds in 1970, claims have been made that large doses prevent or cure the common cold. Numerous experiments have failed to produce any clear-cut indication that vitamin C in any dosage protects against or ameliorates the symptoms of the common cold... Overall, there is no indication in the current knowledge of biochemistry and physiology or in controlled studies that the use of ascorbic acid (Vitamin C) can prevent or cure acute or chronic respiratory infections.

WHAT IS THE DIFFERENCE BETWEEN THE COMMON COLD AND THE FLU?

The flu refers to a syndrome usually caused by influenza virus, hence the origin of the term "flu." Other viruses can also cause this syndrome, although not usually the same ones as cause the common cold.

Apart from the type of causative virus, the main difference between the flu and the common cold is the degree and type of symptoms. The flu usually appears suddenly and within a day you feel very ill. Profound malaise is characteristic, accompanied by dry cough and fever, often to 103° or higher. By contrast, cold symptoms usually build up over one or more days and, although the symptoms are annoying, you don't feel systemically ill. Runny nose, watery eyes and sneezing – all characteristic of the common cold – are usually absent in the flu.

The flu also tends to last longer than a cold. Once the fever and ill feeling have abated, symptoms of weakness or lethargy may persist for another week or so. The symptoms of a cold are usually completely gone within a week after it began.

Most patients with the flu recover uneventfully. However, complications can occur.

WHAT ARE THE COMPLICATIONS OF THE FLU?

Even without complications most flu sufferers are very ill and feel fortunate to recover in a week or so. Influenza is a systemic disease and for a small number of patients major complications can occur. Most of these are bacterial infections, particularly bacterial pneumonia (see Section N). Bacterial pneumonia was probably responsible for most of the deaths in the great influenza pandemic of 1918.

Other complications are encephalitis (inflammation of the brain), other nervous system disorders, and kidney failure. People most prone to develop complications during flu epidemics are the elderly and debilitated, those with chronic diseases, or those have a compromised immune system. Military recruits and others living in a very close quarters are also at increased risk of flu complications.

ARE SMOKERS MORE LIKELY TO GET THE FLU?

It appears so. And to get it more severely. During a flu outbreak (influenza A) among young Israeli soldiers, doctors were careful to note which patients were smokers and which were not. They found that 68.5 percent of smokers came down with the flu, compared with only 47.2 percent of nonsmokers (see Kark, et al). In other words, smokers were about one and a half times more likely to contract the flu than were nonsmokers. Also, among those recruits who did get the flu, smokers were likely to have a more severe case. This result (more likely to get the flu, and more severely) has been supported by other studies in other countries.

What about other viral syndromes? Another large study (Aronson, et al) found that acute respiratory tract illness (ARTI) was more common and more severe in smokers. Over 1,000 people reporting acute respiratory symptoms (cough, chest congestion, swollen neck glands, sore throat) to an outpatient clinic were asked about their smoking habits. The result? Smokers were much more likely to contract ARTI than nonsmokers, and to get it more severely.

To summarize, not only does cigarette smoking have the severe effects outlined in Section S, it also contributes to the occurrence and severity of common respiratory infections.

HOW IS THE FLU PREVENTED?

The flu vaccine is designed to prevent influenza. When given before the onset of a flu epidemic, it can prevent an estimated 70 to 90 percent of cases that would otherwise occur. Unfortunately, the viruses responsible for the flu change their characteristics every one to three years, so the vaccine also has to be changed frequently to be effective. Furthermore, these changes in vaccine have to be made in anticipation of the viral strains that will cause the flu. Such predictions are not always accurate. In 1976 many older citizens received the swine flu vaccine in anticipation of an epidemic that fortunately did not occur.

The flu vaccine is made from killed virus, and each year's vaccine includes several strains. For example, the vaccine for 1983­84 contained both A and B influenza virus strains (A/Brazil/78, A/Philippines/82 and B/Singapore/79), in a single 0.5 ml dose for injection.

Vaccination to prevent flu is recommended for patients with chronic or debilitating disease, such as severe emphysema, chronic bronchitis, heart disease that may lead to heart failure, chronic kidney failure, cancer, and so forth. The United States Public Health Service also recommends flu vaccine for individuals over 65. Usage for a pregnant woman should be along the same guidelines as for the general population. There is no evidence that flu vaccine causes harm to mother or fetus (the vaccine does not contain live virus). Even so, if it must be given to a pregnant woman, the PHS recommends waiting until the second or third trimester.

Because it is made from killed virus, the vaccine itself will not cause the flu. However, reactions can occur, though not as often as with the older vaccines used several years ago. Some people will experience a red, tender area where the shot is given. A few may also get a slight fever with chills and headache that abates in one to two days. An allergic reaction can also occur, presumably due to the egg protein since the virus is grown in eggs, but this reaction is very rare.

Perhaps the most dreaded reaction is the Guillain Barré syndrome (GBS). This is ascending paralysis that can lead to respiratory failure and death (see Section L). It is a rare occurrence from the vaccine and can also occur from the flu itself. In the 1976 swine flu program GBS occurred in approximately one out of every 100,000 persons vaccinated and was fatal in one in 20 who came down with the syndrome. A GBS surveillance program begun in 1978 has uncovered no excess cases of GBS with influenza vaccine used since then. According to the PHS, "any risk of GBS from influenza vaccine appears to be far lower than the risks associated with influenza among persons for whom the vaccine is indicated" (MMWR 31:26, July 9, 1982, 352).

IS THERE ANY TREATMENT FOR THE FLU?

For years the standard treatment for the flu has been bed rest, plenty of fluids, and aspirin to control symptoms. This is still recommended, for in fact the illness is self­limiting and the vast majority of patients get better without complications.

A new anti­viral drug has changed this approach for some influenza victims. Although very few anti­viral drugs are available, one in particular has proved effective against the influenza A strain of virus. The drug is amantadine (trade name Symmetrel). In several studies of patients during small outbreaks of influenza A, amantadine has been shown to:

1. Prevent or greatly ameliorate the flu syndrome when taken before symptoms occur, in essence acting as a prophylactic medication.

2. Attenuate the course of the flu after the illness has begun, when given during the first 48 hours of symptoms.

Most of these studies have been in chronically ill patients who run a high risk of complications from influenza A infections. However, in one study of college students, those receiving amantadine returned to their classes earlier and shed smaller amounts of virus than those receiving a placebo (an inert substance).

Amantadine has relatively minor side effects, mainly lightheadedness; when compared with flu symptoms the side effects appear a reasonable trade­off. At present the drug appears most useful in people who run a definite risk of contracting influenza A infection (as during a defined outbreak). It is not indicated for the individual patient who has the flu syndrome as an isolated case, unless the patient is very ill and the flu can be attributed to the influenza A virus.

WHAT OTHER RESPIRATORY INFECTIONS ARE CAUSED BY VIRUSES?

Besides the common cold and flu syndromes, viruses can cause other types of respiratory infections.

Pneumonia: This is an infection of one or both lungs manifested by fluid and inflammation in the alveolar air spaces. Influenza virus can itself cause a pneumonia or can make the patient susceptible to a bacterial pneumonia. Pneumonia is discussed in Section N.

Bronchiolitis: This viral infection is limited to the smaller airways, called bronchioles. It is more common in children than in adults.

Laryngo­Tracheo­Bronchitis: An infection of the trachea, larynx (voice box), and large bronchi. It occurs most commonly in children where it is also called croup, because of the characteristic "croupy" cough, a high­pitched barking sound.

Pharyngitis: An infection of the throat, the area behind and below the tongue.

With any of these infections the patient may feel systemically ill, run a high fever, and require several days for complete recovery.

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