common cold
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What is the common cold?
The common cold is an acute viral infection primarily affecting the upper respiratory tract, but it can spread to the lower respiratory structures and cause secondary infections. Over 200 agents, especially rhinoviruses, can cause cold symptoms. Transmission occurs through exposure to infected individuals, often before symptoms appear. Symptoms include sneezing, headache, fatigue, and nasal discharge. The incidence of colds increases during autumn and winter, possibly due to more time spent indoors. The illness typically lasts about five to seven days, though a cough may linger.
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What causes the common cold?
The common cold is an acute viral infection that starts in the upper respiratory tract. Over 200 agents can cause cold symptoms, but rhinoviruses are the most frequent cause; there are around 100 different strains of rhinovirus associated with coldlike illness in humans. Other viruses that can cause the common cold include parainfluenza, influenza, respiratory syncytial viruses, reoviruses, and adenoviruses.
The cold is caught from exposure to infected people, who can carry and communicate the virus without experiencing symptoms. The viruses start spreading from an infected person before symptoms appear, peaking during the symptomatic phase.
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What are the main symptoms of a common cold?
The common cold, an acute viral infection, typically starts in the upper respiratory tract and sometimes spreads to the lower structures. Over 200 agents, especially rhinoviruses, can cause it.
Symptoms vary but often include sneezing, headache, fatigue, chills, and sore throat. Nasal issues such as rhinitis and discharge are also typical; the discharge starts as a clear fluid that thickens and changes color as the illness progresses. Though there is usually no fever, coughing may develop as the virus penetrates deeper. Symptoms usually last five to seven days, but a cough may linger.
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How does the common cold spread from person to person?
The common cold, a viral infection, spreads through respiratory droplets produced when an infected person coughs or sneezes. Transmission typically occurs when people are within six feet of each other.
The viruses that cause colds can also persist on surfaces for hours or days and spread when a person touches a contaminated surface and then touches their mouth, nose, or eyes. The spread is most likely when a person is symptomatic, but it can also occur before symptoms appear.
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Why do antibiotics not work against the common cold?
Antibiotics are ineffective against the common cold because the common cold is a viral infection, whereas antibiotics target bacteria. Viruses and bacteria differ significantly in structure and how they cause infection. Antibiotics work by inhibiting bacterial cell wall synthesis or protein synthesis, or by interfering with the function of the cell membrane, all of which are ineffective against viruses. Because viruses aren't alive, they cannot be killed; rather, they must run their course while the body's immune system fights them off.
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What can people do to prevent catching or spreading the common cold?
To avoid catching or spreading the common cold, it's best to prevent infection. The CDC recommends several measures to minimize the spread of respiratory illnesses:
- Avoid close contact with sick individuals.
- Refrain from touching your eyes, nose, and mouth.
- Frequently wash your hands with soap and water for a minimum of 20 seconds.
The common cold is caused by over 200 viruses, with rhinoviruses being the most frequent. Symptoms include a runny nose, cough, and sometimes a sore throat, but are usually mild with rare instances of fever and aches.
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common cold, acute viral infection that starts in the upper respiratory tract, sometimes spreads to the lower respiratory structures, and may cause secondary infections in the eyes or middle ears. More than 200 agents can cause symptoms of the common cold, including parainfluenza, influenza, respiratory syncytial viruses, and reoviruses. Rhinoviruses, however, are the most frequent cause, and some 100 different strains of rhinoviruses have been associated with coldlike illness in humans.
The popular term common cold reflects the feeling of chilliness on exposure to a cold environment that is part of the onset of symptoms. The cold is caught from exposure to infected people. People can carry the virus and communicate it without experiencing any of the symptoms themselves. Incubation is short—usually one to four days. The viruses start spreading from an infected person before the symptoms appear, and the spread reaches its peak during the symptomatic phase. The incidence of colds peaks during the autumn, and minor epidemics commonly occur throughout the winter. The reason for this incidence is unknown; it may result from the greater amount of time spent indoors, which increases the likelihood of close contact with those persons carrying cold viruses. Young children can contract between three and eight colds a year; they usually come into contact with the infectious agents in day-care centres or preschools.
Cold symptoms vary from person to person, but in the individual the same symptoms tend to recur in succeeding bouts of infection. Symptoms may include sneezing, headaches, fatigue, chills, sore throat, inflammation of the nose (rhinitis), and nasal discharge. There is usually no fever. The nasal discharge is the first warning that one has caught a cold. Once a virus becomes established on the respiratory surface of the nose, its activities irritate the nose’s cells, which respond by pouring out streams of clear fluid. This fluid acts to dilute the virus and clear it from the nose. The sensory organs in the nose are stung by the inflammatory reaction, thereby setting up sneezing, a second method of expelling the virus. If the virus penetrates more deeply into the upper respiratory tract, coughing is added to the infected person’s symptoms in a further effort to get rid of the virus. Coughing can be dry or produce amounts of mucus. Symptoms abate as the host’s defenses increase, the clear fluid often changing to a thick, yellow-green fluid that is full of the debris of dead cells. The usual duration of the illness is about five to seven days, but lingering cough and postnasal discharge may persist for two weeks or more.
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Diagnosis of a cold is usually made by medical history alone, although it is possible to take a culture for viruses. There is no effective antiviral agent available for the common cold. Therapy consists of treating the symptoms—relieving aches, fever, and nasal congestion. One of the greatest medical controversies in the past few decades concerned the efficacy of vitamin C (ascorbic acid) in the prevention or treatment of the common cold. In many studies, administration of ascorbic acid failed to prevent or decrease the symptoms of the common cold.