Infection: Common Cold

Definition
Description
Demographics
Causes and Symptoms
Diagnosis
Treatment
Prognosis
Prevention
The Future
For more information

Definition

The common cold is a contagious viral infection of the upper respiratory tract (nose and throat). It is self-limiting, meaning that it clears up by itself without the need for special medical treatment.

The disease got its name in the sixteenth century, when English doctors noticed that colds are more frequent in northern countries during the winter months and thought that exposure to low temperatures caused colds. It was not until the eighteenth century that Benjamin Franklin suggested that cold weather by itself does not cause colds but helps them to spread by driving people indoors where they are crowded more closely together. Although viruses had not been discovered by Franklin's day, he was correct in thinking that colds are transmitted from one person to another through the air or by direct contact.

Description

The common cold is one of the most widespread infectious diseases in the world. It is caused by about 200 different viruses belonging to at least eight different families of viruses. For most people, the classic symptoms of a cold are an irritated nose or scratchy throat within eight hours to two days after infection, followed quickly by a runny nose and sneezing. Although many people experience headaches, general tiredness, and loss of appetite as well, the main symptoms of a cold are in the nose.

A person can get a cold by inhaling the virus directly if they are sitting close to an infected person who is sneezing or coughing. They can also get a cold by touching their eyes, nose, or mouth after touching an object or

surface contaminated by the virus. Research indicates that cold viruses can live on skin for as long as two hours and on drinking glasses or other hard surfaces for as long as four days.

People with colds are most likely to spread the virus to others during the first two to three days of infection. After that they are much less contagious.

Demographics

No exact statistics are kept on the number of colds each year in the United States or in any other country because the illness is so common and many people take care of their symptoms at home. The Centers for Disease Control and Prevention (CDC) estimates that people in the United States suffer about 1 billion colds every year; children lose between 22 and 189 million school days in an average year, and their parents lose 126 million work days to stay home and take care of them. Other employees miss an average of 150 million work days every year because of colds. The total impact of colds on the American economy comes to an estimated $20 billion per year.

Colds are equally common in people of all races and ethnic groups. Some studies indicate that boys younger than three are more likely than girls to get colds in day care settings; however, in older children and adults, males and females are equally likely to get colds. In terms of age, children get colds more frequently than adults. Children average three to eight colds every year, and parents frequently get colds from their children. Colds become less frequent in later life, however; on average, people over sixty have less than one cold a year.

Colds are more common in North America during the fall and winter months, when children are in school and adults are spending more time indoors. In tropical climates, colds are most common during the rainy season, as humid conditions increase the viruses' survival time outside the human body.

Causes and Symptoms

The common cold is caused by at least 200 viruses that had been identified as of 2008. A cold virus typically enters the body through the nasal

passages or mouth, but can also enter through the mucous membranes covering the eyes. The virus spreads to the tissues lining the area between the nose and the back of the throat, where it rapidly multiplies. Within hours or a day or two after the virus enters the body, the infected person feels a scratchy sensation at the back of the throat, followed by sneezing and a constant flow of runny mucus from the nose. Researchers think that these symptoms are caused by the body's immune response to the virus rather than by tissue damage caused by the virus.

Home Care for Colds

Most people with colds do not need to see a doctor. They can relieve cold symptoms at home by using one or more of the following treatments:

• Rest at home rather than going to school or work. Trying to keep up a normal schedule of activities outside the house exposes other people to the cold virus.
• Drink plenty of fluids. Some people find herbal teas containing licorice, chamomile, lemon, or ginger soothing to inflamed throat tissues.
• Take a mild over-the counter pain reliever for headache, fever, or muscle cramps.
• Use a decongestant nasal spray to relieve a stuffed-up nose. These sprays should not be used for more than a few days, however, because they can dry out the membranes lining the nasal passages. In addition, they should not be used more frequently than recommended on the package. Overuse of decongestants can lead to a rebound reaction, in which the nasal passages react to the decongestant by becoming even more swollen and irritated.
• Take an antihistamine. Some people are helped by such preparations as Benadryl or Nytol, which slow down the secretion of mucus and relieve a runny nose. Antihista-mines do, however, make many people drowsy and are best used before bedtime.
• Cough medicines. These preparations should not be given to children because of the possibility of side effects but may provide temporary relief for adults from coughing due to a cold.

Although claims have been made that taking zinc, large amounts of vitamin C, or extracts of echinacea will help to cure a cold, there is no convincing evidence for the effectiveness of any of these substances.

In addition to the runny nose, sneezing, and coughing associated with the common cold, people may also have:

• Low-grade fever (101°F [38.8°C] or lower)
• Muscle aches
• Headache
• Loss of the senses of taste and smell

• Loss of appetite
• Sore throat

Children are often sicker than adults when they get a cold because their immune systems are less developed. Children may run a fever as high as 102°F (38.9°C) with a cold; they may also develop an ear or sinus infection following a cold. Children with asthma may have an attack triggered by a cold.

Diagnosis

For most people, the diagnosis of a cold is obvious from its symptoms, particularly if they know they have recently been exposed to someone else with a cold. Most people do not need to see a doctor to be diagnosed with a cold. They should, however, see their doctor if they have any of the following symptoms, which may indicate an allergy or a more serious illness:

• The symptoms last longer than two weeks.
• The patient has a fever of 102°F (38.9°C) or higher.
• They are coughing up thick mucus.
• They have severely swollen glands.
• They have severe pain in the sinuses.
• They are having chills or night sweats, or are extremely fatigued.

Treatment

There is no cure for the common cold. Treatment is aimed at relieving the sneezing and other symptoms until the body's immune system clears the virus. The sidebar lists some common home and over-the-counter remedies that ease the symptoms of a cold.

Although many people ask their doctors for antibiotics to treat a cold, it is important to know that antibiotics are not effective against viruses. In fact, overprescribing of antibiotics is a major factor in the emergence and spread of antibiotic-resistant bacteria. The doctor will, however, prescribe antibiotics if the patient has developed a sinus infection caused by bacteria.

Prognosis

Most people recover from a cold in seven to eleven days with no long-term complications. Children, however, may develop earaches following a cold.

Prevention

There is no vaccine effective against colds. The following precautions, however, can lower a person's risk of getting frequent colds:

• Stay away from people with colds whenever possible.
• Wash the hands frequently.
• Avoid touching the mouth and face after being exposed to someone with a cold.
• Use alcohol-based hand sanitizers.
• Keep kitchen and bathroom countertops and other surfaces clean.
• Wash children's toys after play.
• Do not share drinking glasses, cups, or food utensils. Use disposable paper cups when sick to protect other family members.

The Future

Several drug companies are working on antiviral drugs that might help people recover from colds more rapidly. One such drug is being tested in an oral form while a second drug is being developed that would be applied as a nasal spray. One limitation of these drugs, however, is that they would work only against cold viruses belonging to one of the eight groups known to cause the common cold.

The development of an effective vaccine against colds is considered unlikely. One reason is the sheer number of viruses known to cause colds. Another reason is that these viruses mutate (change their DNA) very rapidly; thus any vaccine that might be developed would be outdated by the time it entered clinical trials, let alone be approved for use.

SEE ALSO Asthma; Ear infection; Influenza; Sore throat

WORDS TO KNOW

Echinacea: A plant native to the eastern United

States that is thought by some to be a useful cold remedy. It is also known as purple coneflower.

Mutate: A change in the genetic material of organism. Viruses can mutate rapidly.

For more information

BOOKS

Blenkinsopp, Alison, Paul Paxton, and John Blenkinsopp. Symptoms in the Pharmacy: A Guide to the Management of Common Illness, 5th ed. Malden, MA: Blackwell Publishing, 2005.

Landau, Elaine. The Common Cold. New York: Marshall Cavendish Benchmark, 2009.

Tyrrell, David, and Michael Fielder. Cold Wars: The Fight against the Common Cold. New York: Oxford University Press, 2002. This book is a history of humans' attempts to cure the common cold as well as an account of present research into new treatments.

PERIODICALS

Mason, Michael. “Sniffling, Sneezing, and Turning Cubicles into Sick Bays.” New York Times, December 26, 2006. Available online at http://www.nytimes.com/2006/12/26/health/26cons.html?_r=1&oref=slogin (accessed July 22, 2008). This is a news item about the increasing tendency of people to go to school or work even when they are sick with a bad cold.

WEB SITES

American Academy of Otolaryngology—Head and Neck Surgery. Antihista-mines, Decongestants, and Cold Remedies. Available online at http://www.entnet.org/HealthInformation/coldRemedies.cfm (updated January 2008; accessed July 23, 2008).

Mayo Clinic. Common Cold. Available online at http://www.mayoclinic.com/health/common-cold/DS00056 (updated September 14, 2007; accessed July 22, 2008).

National Institute of Allergy and Infectious Diseases (NIAID). Common Cold. Available online at http://www3.niaid.nih.gov/healthscience/healthtopics/colds/default.htm (updated December 10, 2007; accessed July 22, 2008).

Virtual Medical Centre. Upper Respiratory Infection Animation. Available online at http://www.virtualrespiratorycentre.com/diseases.asp?did=10 (accessed July 23, 2008). The animation describes the process of infection by a cold virus. It takes about a minute and a half to play.