Common cold
The common cold or the cold is a viral infectious disease of the upper respiratory tract that primarily affects the respiratory mucosa of the nose, throat, sinuses, and larynx.[6][8] Signs and symptoms may appear fewer than two days after exposure to the virus.[6] These may include coughing, sore throat, runny nose, sneezing, headache, and fever.[3][4] People usually recover in seven to ten days,[3] but some symptoms may last up to three weeks.[7] Occasionally, those with other health problems may develop pneumonia.[3]
Not to be confused with influenza.Common cold
Usually none, but occasionally otitis media, sinusitis, pneumonia and sepsis can occur[5]
~2 days from exposure[6]
Viral (usually rhinovirus)[8]
Based on symptoms
Hand washing, cough etiquette, social distancing, vitamin C[3][10]
2–3 per year (adults)
6–8 per year (children)[13]
Well over 200 virus strains are implicated in causing the common cold, with rhinoviruses, coronaviruses, adenoviruses and enteroviruses being the most common.[14] They spread through the air during close contact with infected people or indirectly through contact with objects in the environment, followed by transfer to the mouth or nose.[3] Risk factors include going to child care facilities, not sleeping well, and psychological stress.[6] The symptoms are mostly due to the body's immune response to the infection rather than to tissue destruction by the viruses themselves.[15] The symptoms of influenza are similar to those of a cold, although usually more severe and less likely to include a runny nose.[6][16]
There is no vaccine for the common cold.[3] The primary methods of prevention are hand washing; not touching the eyes, nose or mouth with unwashed hands; and staying away from sick people.[3] Some evidence supports the use of face masks.[10] There is also no cure, but the symptoms can be treated.[3] Zinc may reduce the duration and severity of symptoms if started shortly after the onset of symptoms.[11] Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen may help with pain.[12] Antibiotics, however, should not be used, as all colds are caused by viruses,[17] and there is no good evidence that cough medicines are effective.[6][18]
The common cold is the most frequent infectious disease in humans.[19] Under normal circumstances, the average adult gets two to three colds a year, while the average child may get six to eight.[8][13] Infections occur more commonly during the winter.[3] These infections have existed throughout human history.[20]
Diagnosis
The distinction between viral upper respiratory tract infections is loosely based on the location of symptoms, with the common cold affecting primarily the nose (rhinitis), throat (pharyngitis), and lungs (bronchitis).[8] There can be significant overlap, and more than one area can be affected.[8] Self-diagnosis is frequent.[4] Isolation of the viral agent involved is rarely performed,[49] and it is generally not possible to identify the virus type through symptoms.[4]
Prevention
The only useful ways to reduce the spread of cold viruses are physical and engineering measures[10] such as using correct hand washing technique and face masks; in the healthcare environment, gowns and disposable gloves are also used.[10] Droplet precautions cannot reliably protect against inhalation of common-cold-laden aerosols. Instead, airborne precautions such as respirators, ventilation, and HEPA/high MERV filters, are likely the only reliable protection against cold-laden aerosols.[36] Isolation or quarantine is not used as the disease is so widespread and symptoms are non-specific. There is no vaccine to protect against the common cold.[50] Vaccination has proven difficult as there are many viruses involved and they mutate rapidly.[10][51] Creation of a broadly effective vaccine is, therefore, highly improbable.[52]
Regular hand washing appears to be effective in reducing the transmission of cold viruses, especially among children.[53] Whether the addition of antivirals or antibacterials to normal hand washing provides greater benefit is unknown.[53] Wearing face masks when around people who are infected may be beneficial; however, there is insufficient evidence for maintaining a greater social distance.[53]
It is unclear whether zinc supplements affect the likelihood of contracting a cold.[54] Routine vitamin C supplements do not reduce the risk or severity of the common cold, though they may reduce its duration.[55]
Prognosis
The common cold is generally mild and self-limiting with most symptoms generally improving in a week.[8] In children, half of cases go away in 10 days and 90% in 15 days.[91] Severe complications, if they occur, are usually in the very old, the very young, or those who are immunosuppressed.[19] Secondary bacterial infections may occur resulting in sinusitis, pharyngitis, or an ear infection.[92] It is estimated that sinusitis occurs in 8% and ear infection in 30% of cases.[93]
Research directions
Antivirals have been tested for effectiveness in the common cold; as of 2009, none had been both found effective and licensed for use.[81] There are trials of the anti-viral drug pleconaril which shows promise against picornaviruses as well as trials of BTA-798.[106] The oral form of pleconaril had safety issues and an aerosol form is being studied.[106] The genomes of all known human rhinovirus strains have been sequenced.[107]
Societal impact
The economic impact of the common cold is not well understood in much of the world.[93] In the United States, the common cold leads to 75–100 million physician visits annually at a conservative cost estimate of $7.7 billion per year. Americans spend $2.9 billion on over-the-counter drugs and another $400 million on prescription medicines for symptom relief.[108] More than one-third of people who saw a doctor received an antibiotic prescription, which has implications for antibiotic resistance.[108] An estimated 22–189 million school days are missed annually due to a cold. As a result, parents missed 126 million workdays to stay home to care for their children. When added to the 150 million workdays missed by employees who have a cold, the total economic impact of cold-related work loss exceeds $20 billion per year.[56][108] This accounts for 40% of time lost from work in the United States.[109]
Notes
Bibliography