Chapter 371 The Common Cold
The common cold is a viral illness in which the symptoms of rhinorrhea and nasal obstruction are prominent; systemic symptoms and signs such as headache, myalgia, and fever are absent or mild. It is often termed rhinitis but includes self-limited involvement of the sinus mucosa and is more correctly termed rhinosinusitis.
The most common pathogens associated with the common cold are the rhinoviruses (Chapter 255), but the syndrome can be caused by many different viruses (Table 371-1). The role of bocavirus as a cause of colds is uncertain because the virus is often isolated from patients who are co-infected with other recognized pathogens.
Table 371-1 PATHOGENS ASSOCIATED WITH THE COMMON COLD
| ASSOCIATION | PATHOGEN | RELATIVE FREQUENCY* |
|---|---|---|
| Agents primarily associated with colds | Rhinoviruses | Frequent |
| Coronaviruses | Occasional | |
| Agents primarily associated with other clinical syndromes that also cause common cold symptoms | Respiratory syncytial viruses | Occasional |
| Human metapneumovirus | Occasional | |
| Influenza viruses | Uncommon | |
| Parainfluenza viruses | Uncommon | |
| Adenoviruses | Uncommon | |
| Enteroviruses | Uncommon | |
| Bocavirus | Uncommon |
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 associated with cold symptoms. The highest incidence of rhinovirus infection occurs in the early fall (August-October) and in the late spring (April-May). The seasonal incidence for parainfluenza viruses (Chapter 251) usually peaks in the late fall and late spring and is highest between December and April for respiratory syncytial virus (RSV; Chapter 252) and influenza viruses (Chapter 250).
Young children have an average of 6-8 colds per year, but 10-15% of children have at least 12 infections per year. The incidence of illness decreases with age, with 2 to 3 illnesses per year by adulthood. The incidence of infection is primarily a function of exposure to the virus. Children in out-of-home daycare centers during the 1st year of life have 50% more colds than children cared for only at home. The difference in the incidence of illness between these groups of children decreases as the length of time spent in daycare increases, although the incidence of illness remains higher in the daycare group through at least the 1st 3 yr of life. Mannose-binding lectin deficiency with impaired innate immunity may be associated with an increased incidence of colds in children.
Viruses that cause the common cold are spread by small-particle aerosols, large-particle aerosols, and direct contact. Although the different common cold pathogens can presumably be spread by any of these mechanisms, some routes of transmission appear to be more efficient than others for particular viruses. Studies of rhinoviruses and RSV suggest that direct contact is an efficient mechanism of transmission of these viruses, although transmission by large-particle aerosols can also occur. In contrast to rhinoviruses and RSV, influenza viruses appear to be most efficiently spread by small-particle aerosols.
The respiratory viruses have evolved different mechanisms to avoid host defenses. Infections with rhinoviruses and adenoviruses result in the development of serotype-specific protective immunity. Repeated infections with these pathogens occur because there are a large number of distinct serotypes of each virus. Influenza viruses have the ability to change the antigens presented on the surface of the virus and thus behave as though there were multiple viral serotypes. The interaction of coronaviruses (Chapter 256) with host immunity is not well defined, but it appears that multiple distinct strains of coronaviruses are capable of inducing at least short-term protective immunity. The parainfluenza viruses and RSV each have a small number of distinct serotypes. Reinfection with these viruses occurs because protective immunity to these pathogens does not develop after an infection. Although reinfection is not prevented by the adaptive host response to these viruses, the severity of subsequent illness is moderated by pre-existing immunity.
Viral infection of the nasal epithelium can be associated with destruction of the epithelial lining, as with influenza viruses and adenoviruses, or there can be no apparent histologic damage, as with rhinoviruses and RSV. Regardless of the histopathologic findings, infection of the nasal epithelium is associated with an acute inflammatory response characterized by release of a variety of inflammatory cytokines and infiltration of the mucosa by inflammatory cells. This acute inflammatory response appears to be responsible, at least in part, for many of the symptoms associated with the common cold. Inflammation can obstruct the sinus ostium or eustachian tube and predispose to bacterial sinusitis or otitis media.
The onset of common cold symptoms typically occurs 1-3 days after viral infection. The 1st symptom noted is often sore or scratchy throat, followed closely by nasal obstruction and rhinorrhea. The sore throat usually resolves quickly and, by the 2nd and 3rd day of illness, nasal symptoms predominate. Cough is associated with ∼30% of colds and usually begins after the onset of nasal symptoms. Influenza viruses, RSV, and adenoviruses are more likely than rhinoviruses or coronaviruses to be associated with fever and other constitutional symptoms. The usual cold persists for about 1 wk, although 10% last for 2 wk.
The physical findings of the common cold are limited to the upper respiratory tract. Increased nasal secretion is usually obvious; a change in the color or consistency of the secretions is common during the course of the illness and does not indicate sinusitis or bacterial superinfection. Examination of the nasal cavity might reveal swollen, erythematous nasal turbinates, although this finding is nonspecific and of limited diagnostic value.
The most important task of the physician caring for a patient with a cold is to exclude other conditions that are potentially more serious or treatable. The differential diagnosis of the common cold includes noninfectious disorders as well as other upper respiratory tract infections (Table 371-2).
Table 371-2 CONDITIONS THAT CAN MIMIC THE COMMON COLD
| CONDITION | DIFFERENTIATING FEATURES |
|---|---|
| Allergic rhinitis | Prominent itching and sneezing Nasal eosinophils |
| Foreign body | Unilateral, foul-smelling secretions Bloody nasal secretions |
| Sinusitis | Presence of fever, headache or facial pain, or periorbital edema or persistence of rhinorrhea or cough for >14 days |
| Streptococcosis | Mucopurulent nasal discharge that excoriates the nares |
| Pertussis | Onset of persistent or severe cough |
| Congenital syphilis | Persistent rhinorrhea with onset in the 1st 3 mo of life |
Routine laboratory studies are not helpful for the diagnosis and management of the common cold. A nasal smear for eosinophils may be useful if allergic rhinitis is suspected (Chapter 137). A predominance of polymorphonuclear leukocytes in the nasal secretions is characteristic of uncomplicated colds and does not indicate bacterial superinfection.
The viral pathogens associated with the common cold can be detected by polymerase chain reaction (PCR), culture, antigen detection, or serologic methods. These studies are generally not indicated in patients with colds because a specific etiologic diagnosis is useful only when treatment with an antiviral agent is contemplated. Bacterial cultures or antigen detection are useful only when group A streptococcus (Chapter 176), Bordetella pertussis (Chapter 189), or nasal diphtheria (Chapter 180) is suspected. The isolation of other bacterial pathogens is not an indication of bacterial nasal infection and is not a specific predictor of the etiologic agent in sinusitis.
The management of the common cold consists primarily of symptomatic treatment.
Specific antiviral therapy is not available for rhinovirus infections. Ribavirin, which is approved for treatment of RSV infections, has no role in the treatment of the common cold. The neuraminidase inhibitors oseltamivir and zanamivir have a modest effect on the duration of symptoms associated with influenza viral infections in children. Oseltamivir also reduces the frequency of influenza-associated otitis media. The difficulty of distinguishing influenza from other common cold pathogens and the necessity that therapy be started early in the illness (within 48 hr of onset of symptoms) to be beneficial are practical limitations to the use of these agents for mild upper respiratory tract infections. Antibacterial therapy is of no benefit in the treatment of the common cold.
The use of symptomatic therapies in children is controversial; although some of these medications are effective in adults, no studies have demonstrated a significant effect in children. Young children cannot assist in the assessment of symptom severity, so studies of these treatments in children have generally been based on observations by parents or other observers, a method that is likely to be insensitive for detection of treatment effects. The use of symptomatic oral over-the-counter (OTC) therapies (often containing antihistamines, antitussives, and decongestants) in children can only be based on an assumption that the effects of symptomatic treatments may be similar in adults and children. As a result of the lack of direct evidence for effectiveness and the potential for unwanted side effects, the FDA recommends that OTC cough and cold products not be used for infants and children <2 yr of age. Further studies have shown that OTC cough and cold products are ineffective in treating symptoms of children <6 yr of age. A decision whether to use these medications in older children must balance the likelihood of clinical benefit against the potential adverse effects of these drugs. The prominent or most bothersome symptoms of colds vary in the course of the illness and, therefore, if symptomatic treatments are used, it is reasonable to target therapy to specific bothersome symptoms. If symptomatic treatments are recommended, care should be taken to ensure that caregivers understand the intended effect and can determine the proper dosage of the medications.
Fever is not usually associated with an uncomplicated common cold, and antipyretic treatment is generally not indicated.
Either topical or oral adrenergic agents can be used as nasal decongestants. Effective topical adrenergic agents such as xylometazoline, oxymetazoline, or phenylephrine are available as either intranasal drops or nasal sprays. Reduced-strength formulations of these medications are available for use in younger children, although they are not approved for use in children <2 yr old. Systemic absorption of the imidazolines (oxymetazoline, xylometazoline) has very rarely been associated with bradycardia, hypotension, and coma. Prolonged use of the topical adrenergic agents should be avoided to prevent the development of rhinitis medicamentosa, an apparent rebound effect that causes the sensation of nasal obstruction when the drug is discontinued. The oral adrenergic agents are less effective than the topical preparations and are occasionally associated with systemic effects such as central nervous system stimulation, hypertension, and palpitations. Saline nose drops (wash, irrigation) can improve nasal symptoms.
The first-generation antihistamines reduce rhinorrhea by 25-30%. The effect of the antihistamines on rhinorrhea appears to be related to the anticholinergic rather than the antihistaminic properties of these drugs, and therefore the second-generation or “nonsedating” antihistamines have no effect on common cold symptoms. The major adverse effect associated with the use of the antihistamines is sedation, although there is some evidence that this adverse effect is less bothersome in children than in adults. Rhinorrhea may also be treated with ipratropium bromide, a topical anticholinergic agent. This drug produces an effect comparable to the antihistamines but is not associated with sedation. The most common side effects of ipratropium are nasal irritation and bleeding.
The sore throat associated with colds is generally not severe, but treatment with mild analgesics is occasionally indicated, particularly if there is associated myalgia or headache. The use of acetaminophen during rhinovirus infection has been associated with suppression of neutralizing antibody responses, but this observation has no apparent clinical significance. Aspirin should not be given to children with respiratory infections because of the risk of Reye syndrome in children with influenza (Chapter 591).
Cough suppression is generally not necessary in patients with colds. Cough in some patients appears to be due to upper respiratory tract irritation associated with postnasal drip. Cough in these patients is most prominent during the time of greatest nasal symptoms, and treatment with a first-generation antihistamine may be helpful. Sugar-containing cough drops or honey as a demulcent may be temporarily effective. In other patients, cough may be a result of virus-induced reactive airways disease. These patients can have cough that persists for days to weeks after the acute illness and might benefit from bronchodilator therapy. Codeine or dextromethorphan hydrobromide has no effect on cough from colds. Expectorants such as guaifenesin are not effective antitussive agents. The combination of camphor, menthol, and eucalyptus oils may relieve nocturnal cough.
Vitamin C, guaifenesin, and inhalation of warm, humidified air are no more effective than placebo for the treatment of cold symptoms.
Zinc, given as oral lozenges, has been evaluated in several studies as a treatment for common cold symptoms. The function of the rhinovirus 3C protease, an essential enzyme for rhinovirus replication, is inhibited by zinc, but there has been no evidence of an antiviral effect of zinc in vivo. The effect of zinc on symptoms has been inconsistent, with some studies reporting dramatic treatment effects (in adults), whereas other studies find no benefit. A synthesis of these disparate results is difficult, but it appears unlikely that zinc has a clinically significant impact on common cold symptoms in children.
Echinacea is a popular herbal treatment for the common cold. Although echinacea extracts have been shown to have biologic effects, echinacea is not effective as a common cold treatment. The lack of standardization of commercial products containing echinacea also presents a formidable obstacle to the rational evaluation or use of this therapy.
The most common complication of a cold is otitis media (Chapter 632), which is reported in 5-30% of children who have a cold, with the higher incidence occurring in children cared for in a group daycare setting. Symptomatic treatment has no effect on the development of acute otitis media, but treatment with oseltamivir might reduce the incidence of otitis media in patients with influenza.
Sinusitis is another complication of the common cold (Chapter 372). Self-limited sinus inflammation is a part of the pathophysiology of the common cold, but 0.5-2% of viral upper respiratory tract infections in adults, and 5-13% in children, are complicated by acute bacterial sinusitis. The differentiation of common cold symptoms from bacterial sinusitis may be difficult. The diagnosis of bacterial sinusitis should be considered if rhinorrhea or daytime cough persists without improvement for at least 10-14 days or if signs of more-severe sinus involvement such as fever, facial pain, or facial swelling develop. There is no evidence that symptomatic treatment of the common cold alters the frequency of development of bacterial sinusitis.
Exacerbation of asthma is a relatively uncommon but potentially serious complication of colds. The majority of asthma exacerbations in children are associated with the common cold. There is no evidence that treatment of common cold symptoms prevents this complication.
Although not a complication, another important consequence of the common cold is the inappropriate use of antibiotics for these illnesses and the associated contribution to the problem of increasing antibiotic resistance of pathogenic respiratory bacteria. In 1998 in the USA, there were an estimated 25 million primary care office visits for the common cold, with 30% of these visits resulting in an inappropriate prescription for antibiotics.
Chemoprophylaxis or immunoprophylaxis is generally not available for the common cold. Immunization or chemoprophylaxis against influenza can prevent colds caused by this pathogen; influenza is responsible for only a small proportion of all colds. Vitamin C and echinacea do not prevent the common cold.
Hand-to-hand transmission of rhinoviruses followed by self-inoculation can theoretically be blocked by virucidal agents. In the experimental setting, virucidal tissues prevent the contamination of hands with virus during nose-blowing, and hand sanitizers can remove infectious virus from the hands. Under natural conditions, however, neither of these interventions prevents common colds. Handwashing is commonly recommended for prevention of colds, but convincing data for effectiveness are not available.
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