Strategies for preventing the common cold: The current evidence
Although the common cold is usually benign, it can lead to exacerbations of asthma and chronic obstructive pulmonary disease, and it is a leading cause of missed school and work. Strategies for prevention have been directed at interruption of viral transmission between persons, as with the use of virucidal agents or disinfectants, and prevention of infection after acquisition of the pathogen. Hand washing continues to be recommended, but there is no proof that hand sanitizers or virucidal tissues are effective in preventing colds. Prophylactic therapies that have been considered include vitamin C, vitamin E, zinc, Echinacea, ginseng, and probiotics. Although some evidence may suggest possible benefits with zinc and probiotics, for example, overall, the data are insufficient to recommend any of these as prophylaxis for the common cold. (J Respir Dis. 2009;30)
ABSTRACT:Although the common cold is usually benign, it can lead to exacerbations of asthma and chronic obstructive pulmonary disease, and it is a leading cause of missed school and work. Strategies for prevention have been directed at interruption of viral transmission between persons, as with the use of virucidal agents or disinfectants, and prevention of infection after acquisition of the pathogen. Hand washing continues to be recommended, but there is no proof that hand sanitizers or virucidal tissues are effective in preventing colds. Prophylactic therapies that have been considered include vitamin C, vitamin E, zinc, Echinacea, ginseng, and probiotics. Although some evidence may suggest possible benefits with zinc and probiotics, for example, overall, the data are insufficient to recommend any of these as prophylaxis for the common cold. (J Respir Dis. 2009;30)
The common cold is a ubiquitous clinical syndrome caused by a variety of viral pathogens. While most common colds are of little medical significance, these illnesses can have important consequences for some patient populations. Infections caused by rhinoviruses, the most common cause of viral upper respiratory tract illness, are associated with 60% to 70% of asthma exacerbations in school-aged children and are an important contributor to exacerbations of chronic obstructive pulmonary disease. Otitis media and rhinosinusitis frequently occur as complications of common colds.
Another important consequence of the common cold is the inappropriate use of antibiotics. In the United States in 1998, there were an estimated 25 million primary care office visits for the common cold, and 30% of these visits resulted in a prescription for antibiotics.1 This unnecessary use of antibiotics contributes to the problem of increasing antibiotic resistance of pathogenic respiratory bacteria.
Although the medical consequences of the common cold are generally modest, the social and economic effects are substantial. The common cold is a leading cause of missed school and work and is the second most common diagnosis at physician office visits. One study estimated that the total economic impact of non-influenza–related viral respiratory infections approaches $40 billion annually in the United States.2
Treatment of the common cold is limited to symptomatic therapies that have modest efficacy and have no impact on the development of significant complications. Effective prevention would clearly have important medical and socioeconomic benefits. The development of effective prophylaxis, however, presents some unique challenges. Although from a societal perspective, these illnesses have a significant impact, for the individual patient, the common cold is generally benign, relatively short in duration, and self-limited. Thus, useful interventions must be convenient, cheap, and safe. These requirements pose a formidable barrier to the development of effective approaches to prophylaxis.
In this review, we will summarize the evidence for the efficacy of various interventions used to prevent the common cold.
EPIDEMIOLOGY AND PATHOGENESIS
Rhinoviruses represent the most frequent cause of the common cold, but other respiratory viruses-including coronavirus, parainfluenza virus, metapneumovirus, respiratory syncytial virus, and influenza virus-are associated with this syndrome. Colds occur most commonly in young children, with an average incidence of about 6 illnesses per year.3 The incidence decreases with age and by adulthood, the incidence is 2 to 3 per year.
Common colds occur year-round, but the incidence is greatest from the early fall until the late spring, reflecting the seasonal prevalence of the viral pathogens. The risk of acquiring a common cold is primarily determined by exposure to other infected persons. In the general population, household or occupational exposure to young children is the most important determinant of risk.
The route of transmission of viral pathogens has obvious implications for interventions to prevent infection. In general, the viruses that cause the common cold are spread by 3 mechanisms: small particle aerosols, large particle aerosols, and direct contact. Small particle aerosols form droplet nuclei that do not settle and can be transmitted over relatively long distances by airflow and may be deposited in the lower airway. Large particle aerosols are droplets generated from the airway that settle rapidly are transmitted only over relatively short distances. These particles are generally filtered by the upper respiratory tract and are not deposited in the lower respiratory tract.
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