The common cold is a self-limited contagious illness that can be caused by a number of different types of viruses. The common cold is medically referred to as a viral upper respiratory tract infection. Symptoms of the common cold may include cough, sore throat, nasal congestion, runny nose, and sneezing. More than 200 different types of viruses are known to cause the common cold, with rhinovirus causing approximately 30%-35% of all adult colds.
Other commonly implicated viruses include coronavirus, adenovirus, respiratory syncytial virus, and parainfluenza virus. Because so many different viruses can cause a cold and because new cold viruses constantly develop, the body never builds up resistance against all of them.
For this reason, colds are a frequent and recurring problem. In fact, children in preschool and elementary school can have six to 12 colds per year while adolescents and adults typically have two to four colds per year. The common cold occurs most frequently during the fall and winter months.
The common cold is the most frequently occurring illness in the world, and it is a leading cause of doctor visits and missed days from school and work. It is estimated that individuals in the United States suffer 1 billion colds per year, with approximately 22 million days of school absences recorded annually.
How is the common cold transmitted?
The common cold is spread either by direct contact with infected secretions from contaminated surfaces or by inhaling the airborne virus after individuals sneeze or cough. Person-to-person transmission often occurs when an individual who has a cold blows or touches their nose and then touches someone or something else.
A healthy individual who then makes direct contact with these secretions can subsequently become infected, often after their contaminated hands make contact with their own eyes or nose. A cold virus can live on objects such as pens, books, telephones, computer keyboards, and coffee cups for several hours and can thus be acquired from contact with these objects.
The symptoms of the common cold typically begin two to three days after acquiring the infection (incubation period).
Symptoms and signs of the common cold vary depending on the virus responsible for the infection and may include the following:
- nasal stuffiness or drainage,
- sore or scratchy throat,
- watery eyes,
- low-grade fever,
- body aches,
The signs and symptoms of the common cold in infants and children are similar to those seen in adults. The cold may begin with a runny nose with clear nasal discharge, which later may become yellowish or greenish in color. Infants and children may also become more fussy and havedecreased appetite.
The symptoms of the common cold will typically last anywhere from four to 14 days, with most individuals improving in one week.
The common cold is a viral infection of the upper respiratory tract. The most commonly implicated virus is a rhinovirus (30–50%), a type of picornavirus with 99 known serotypes. Others include: coronavirus (10–15%), influenza (5–15%), human parainfluenza viruses, human respiratory syncytial virus, adenoviruses, enteroviruses, and metapneumovirus.
In total over 200 serologically different viral types cause colds. Coronaviruses are particularly implicated in adult colds. Of over 30 coronaviruses, 3 or 4 cause infections in humans, but they are difficult to grow in the laboratory and their significance is thus less well-understood. Due to the many different types of viruses and their tendency for continuous mutation, it is impossible to gain complete immunity to the common cold.
Touching eyes, nose, or mouth with contaminated fingers. This behavior increases the likelihood of transferring viruses from the surface of the hands, where they are harmless, into the upper respiratory tract, where they can infect the tissues. It has been demonstrated that cold viruses can be spread by touching contaminated objects and surfaces, or by brief contact of hands.
Spending time in an enclosed area with an infected person or in close contact with an infected person. Common colds are droplet-borne infections, which means that they can be transmitted through breathing in tiny particles that the infected person emits when he or she coughs or sneezes. In one study, the virus was recovered in 1/13 of sneezes and 0/8 coughs generated by adults with natural rhinovirus (cold) infections.
The role of body cooling in causing the common cold is controversial. It is the most commonly offered folk explanation for the disease, and it has received some experimental evidence. One study showed that exposure to the cold causes cold symptoms in about 10% of those exposed, and that the subjects experiencing this effect report far more colds overall than those who do not. However, a variety of other studies do not show such an effect.
A history of smoking extends the duration of illness by about three days.
Getting fewer than seven hours of sleep per night has been associated with a risk three times higher of developing an infection when exposed to a rhinovirus, compared to those who sleep more than eight hours per night.
Common colds are seasonal, occurring more frequently during winter outside of tropical zones. Some argue that this is partly due to a change in behaviors such as increased time spent indoors, which puts infected people in close proximity to other people, rather than to exposure to cold temperatures.
Low humidity increases viral transmission rates. One theory is that dry air causes evaporation of water, thus allowing small viral droplets to disperse farther and stay in the air longer.
Counterintuitively, people with stronger immune systems are more likely to develop symptomatic colds. This is because the symptoms of a cold are directly due to the strong immune response to the virus, not the virus itself.
People with less active immune systems — about a quarter of adults — get infected with the viruses, but the relatively weak immunological response produces no significant or identifiable symptoms. These people are asymptomatic carriers and can unknowingly spread the virus to other people. Because strong immune responses cause cold symptoms, "boosting" the immune system increases cold symptoms.
Though the common cold usually occurs in the fall and winter months, the cold weather itself does not cause the common cold. Rather, it is thought that during cold-weather months people spend more time indoors in close proximity to each other, thus facilitating the spread of the virus. For this same reason, children in day care and school are particularly prone to acquiring the common cold.
There is no cure for the common cold. The common cold is a self-limited illness that will resolve spontaneously with time. Home remedies and treatments are directed at alleviating the symptoms associated with the common cold while the body fights off the infection.
Home treatment for the common cold includes getting rest and drinking plenty of fluids. In older children and adults, over-the-counter medications such as throat lozenges, throat sprays, cough drops, and cough syrups may help relieve symptoms, though they will not prevent or shorten the duration of the common cold. Gargling with warm saltwater may help those with a sore throat.
Decongestants such as pseudoephedrine (Sudafed) or antihistamines may be used for nasal symptoms, while saline nasal sprays may also be beneficial. It is important to note that over-the-counter medications may cause undesirable side effects, therefore they must be taken with care.
Acetaminophen (Tylenol and others) and ibuprofen (Advil, Motrin) can help with fever, sore throat, and body aches.
The treatment for infants and small children with the common cold is supportive as well. It is especially important to allow rest and encourage plenty of fluids in order to prevent dehydration. Nasal drops and bulb suctioning may be used to clear nasal mucus in infants.
Medications such as acetaminophen and ibuprofen may be taken for pain or fever based on the package recommendations for age and weight. Do not use aspirin or aspirin-containing medications in children or teenagers because it has been associated with a rare, potentially fatal condition called Reye's syndrome. Finally, over-the-counter cough and cold medications for infants and children are not recommended.
WARNING: The United States Food and Drug Administration (FDA) recommends that over-the-counter cough and cold medications not be used in children younger than 4 years of age because serious and potentially life-threatening side effects can occur.