A 33-year-old woman who is an ambitious junior executive at a rapidly growing electronics company starts to sneeze frequently at her desk one morning. Later that day, she develops a mild sore throat and rhinorrhea. The rhinorrhea increases over the next four days and is joined by nasal congestion, malaise, and occasional mild headaches. Her symptoms are not debilitating, but they are making it quite hard for the woman to concentrate on her current project-a merger deal that is likely to win her a major promotion. As a result, she goes to her local walk-in clinic and demands an antibiotic that will make her symptoms go away as soon as possible. Vital signs show T = 36.5 C, P = 80, R = 14 and BP = 120/85 mm Hg. Her lungs are clear to auscultation with no rales or wheezes. There is no dullness to percussion. On questioning, she tells the physician that she had been under a great deal of stress at her job and might be experiencing periods of depression. She also reveals that, about two days before her symptoms appeared, she attended a meeting related to the merger deal, at which some of the representatives from the other company were coughing and frequently blowing their noses. There was a lot of hand shaking around the table as progress was made on the terms of the merger.

Question 1.1: What is your diagnosis?

The patient clearly has an upper respiratory infection. (There is no evidence of lower pulmonary involvement.) The lack of fever and myalgias argues against influenza. The most likely diagnosis is acute coryza, better known as the common cold.

Question 1.2: What is the most likely causative agent?

The most likely causative agent is a rhinovirus. Rhinoviruses are members of the Picornaviridae family, a group of small, non enveloped viruses that have an icosahedral capsid and a plus-sense single-stranded RNA genome. Rhinoviruses grow preferentially at 33-34 C-the temperature of the human nasal passages-rather than at the somewhat higher internal temperature (37 C) of the human body. This may explain why they generally do not affect the lower respiratory tract.

Rhinoviruses account for more than 40% of all common colds. The next most frequent causative agents are the coronaviruses, which are thought to be responsible for more than 10% of all cases. Other viruses that can cause colds include adenoviruses, parainfluenza viruses, influenza viruses, and respiratory syncytial viruses.

Question 1.3: How is the causative agent identified?

The different types of viruses that cause common cold produce similar symptoms, so an etiologic diagnosis cannot be made on clinical grounds alone. Rather, rhinovirus infection is diagnosed by isolation of the virus from nasal washes or nasal secretions in tissue culture. This is seldom done in practice, however, because of the benign, self-limiting nature of the disease. In fact, it isn't on the test menu of major reference laboratories.

Question 1.4: Should the patient be given antibiotics?

Absolutely not; antibiotics cannot affect rhinoviruses (or other viruses, for that matter), and they will do nothing for the patient's symptoms. Moreover, the unnecessary use of antibiotics in situations like this may promote the development of drug resistance among bacteria. Zinc gluconate lozenges (now available OTC), taken every two hours, may reduce the duration of the symptoms, but one study showed that they are associated with nausea in 20% of patients. The patient's best bet for partial relief of her symptoms is to try the usual cosmetic treatments, such as OTC decongestants (pseudoephedrine, phenylephrine, or the topical xylometazoline, ipratropium bromide nasal sprays, or antihistamines. Unfortunately, some patients (and this woman may be one of them) don't want to hear that there is no "quick fix" for their ills and will try other physicians in hopes of finding one that will give them a prescription.

Question 1.5: How was this patient infected?

Common colds are most often transmitted by direct person-to-person contact (e.g., during kissing or hand shaking), but they can also be transmitted via droplet infection or fomites. Hand shaking might be the most likely route in this case, but droplet infection could have occurred if any of the executives in the meeting failed to cover their mouths while coughing or sneezing. Transmission on fomites might have occurred if the people in the room shared pens or other items, grabbed the same doorknob, etc. Rhinoviruses persist quite effectively in the environments and are not easily deactivated by low temperature or drying.

Question 1.6: How is this disease prevented?

Thorough hand washing, avoidance of self-inoculation after coming into contact with an infected individual (e.g., by bringing one's hand close to one's nose or mouth after shaking hands with an infected individual), avoidance of direct contact with obviously infected individuals (if possible), the use of tissues to cover one's mouth and nose when coughing or sneezing, and the use of environmental decontamination procedures might help to reduce the rates of transmission. Intranasal application of interferon sprays has proven to be effective in prophylaxis of rhinovirus infections (i.e., in test studies) but is also associated with local irritation of the nasal mucosa. Experimental vaccines to certain rhinovirus serotypes have been developed, but their usefulness is questionable because they do not include all serotypes (over 100 have been described so far), they cannot prevent colds caused by other viruses (e.g., coronaviruses), and there is uncertainty about the mechanisms of immunity. The value of vitamin C in preventing colds has not been proved.

Question 1.7: How common is this disease?

It may well be the most frequently occurring of all diseases, but the actual number of cases is not known because it isn't reported by physicians and most victims just treat themselves. It has been estimated that common colds account for one-half or more of all acute illnesses. In the U.S., the average adult has 2-4 colds per year, while the average child has 6-8 colds per year.