Management of the Common Cold

William A. Kormos

The term common cold describes a self-limited catarrhal illness caused by a variety of respiratory viruses. It is indeed a common problem, with adults averaging two to four colds per year and with almost 7 days lost from work per person per year. Although most patients treat their symptoms at home, physicians are still frequently consulted for upper respiratory infections. The primary task for the physician is to distinguish the common cold from bacterial infections, allergic conditions, and epidemic diseases such as influenza. Once the common cold is diagnosed, reassurance about the self-limited nature of the disease and patient education about its predominantly viral cause is the next step. However, upper respiratory tract infections continue to be a great source of inappropriate use of antibiotics. A recent survey demonstrated that physicians prescribe antibiotics to half of patients labeled as having “colds.” Instead, physicians should be knowledgeable about symptomatic therapies, including over-the-counter remedies. A targeted treatment plan aimed at the predominant symptoms is not only more effective but also more responsible.

PATHOPHYSIOLOGY AND CLINICAL PRESENTATION (1, 2, 3, 4 and 5)

The oropharynx and nasopharynx are lined by a stratified squamous epithelium and are normally teeming with a varied microbial flora. In addition, many potentially pathogenic bacteria can temporarily reside on these epithelial surfaces as “colonizers” without causing true infection. With a few exceptions, such as herpes simplex virus and Epstein-Barr virus, viruses are not usually long-term members of the normal flora of the respiratory tract.

Numerous host defenses protect the upper airway from infection. The first of these defenses is mechanical; particulate matter is expelled by the cough and sneeze reflexes, entrapped by viscous mucous secretions, and propelled outward by ciliary action. In addition, local immunologic defenses attempt to deal with organisms that have breached the mechanical barriers. These defenses include lymphoid tissue, respiratory secretions that contain immunoglobulin A antibodies, and a rich vasculature capable of rapidly delivering phagocytic leukocytes. Once in the nasal cavity, viruses gain access to the upper airway by binding to the intercellular adhesion molecule ICAM-1. Experimental trials are being conducted with a monoclonal antibody to ICAM-1 to block this step in the initiation of infection.

Mechanisms of transmission include airborne transmission of virus-laden respiratory secretions via small, aerosolized particles that remain suspended or large particles that travel only a few feet. However, the most efficient means of transmission is direct mucous membrane contact with virus, usually on contaminated hands. Selfinoculation of viruses surviving on the hands is accomplished by touching one’s nose or eyes. Children are an important reservoir of these viruses. Evidence from prospective, controlled studies suggests that psychological stress, especially chronic life stresses and poor social supports, as well as physical stress, such as lack of sleep, can increase the risk for infection. However, the timeless motherly warning that “you’ll catch cold if you get wet or damp” has not been borne out by experimental studies, which have demonstrated equal susceptibility in chilled and nonchilled hosts.

The common cold is caused by viral agents, mostly from five major families of viruses. Rhinoviruses are the most common viral agents associated with upper respiratory tract illness. Because there are more than 110 antigenic serotypes, crossimmunity does not exist, and reinfection with another serotype right after a recent cold is common. Coronavirus, parainfluenza virus, coxsackievirus, and respiratory syncytial virus account for the rest of the etiologic agents. Influenza A and influenza B produce a more severe syndrome, which overlaps with the common cold. Influenza infection typically occurs in the winter months (December to March) in the Northern Hemisphere.
The clinical syndrome consists of fever and diffuse myalgia, often accompanied by a nonproductive cough and headache. Lack of fever significantly decreases the probability of influenza. Patients with underlying cardiopulmonary disease and the elderly are at a higher risk for the development of a secondary bacterial pneumonia following influenza infection.

Incubation periods for viral upper respiratory infections range from 1 to 5 days; virus shedding lasts up to 3 weeks. Typical symptoms include coryza, pharyngitis, laryngitis, headache, malaise, and fever, in various combinations. Experimental evidence suggests that these symptoms are more the results of the body’s response to the infection (through mediators like bradykinin, prostaglandin, interleukin, and histamine) than the viral infection itself. Ear and sinus discomfort also are often present, frequently caused by mucosal edema that impairs drainage (see Chapters 218 and 219). Whether known as the common cold, nasopharyngitis, or upper respiratory infection, these problems generally resolve spontaneously. Symptoms peak in 3 to 4 days, improve by day 7, but often last for more than 10 days. Common viral upper respiratory infections rarely progress to pneumonia.

DIAGNOSIS (1)

The diagnosis of the “common cold” remains a clinical one, based on the typical presentation. Patients should be examined for localized bacterial infection, such as otitis media, sinusitis, or streptococcal pharyngitis (see Chapters 218, 219 through 220). If the patient presents with symptoms typical of influenza, further diagnostic testing can be considered with rapid testing, in which antibodies to common influenza antigens are usually used. These rapid antigen tests are highly specific, but the sensitivity is only about 60%. PCR-based testing is more sensitive but is also more expensive and time-consuming. Documentation of influenza has therapeutic implications and is useful for tracking the epidemiology of seasonal influenza infection. On the other hand, identification of the specific virus causing the “common cold” is neither practical nor important.