Saturday, March 14, 2009

common cold

common cold is a highly contagious,viral infectious disease of the upper respiratory systems,primaly caused by picornaviruses(including rhinoviruses) or coronaviruses.
after initial infection,the viral replication cycle begins within 8 to 12 hours. symptoms can occur shortly thereafter,and usually begin within 2 to 5 days after infectioun,although occasionally in as little as 10 hours after infection.

the first indication of a cold is often a sore or scratchy throat. other common symptoms are a runny nose,congestion,sneezing,and cough. these are sometimes accompanied by muscle aches,fatigue,malaise,headache,weakness or loss of appetite. the symptoms usually resolve spontaneously in 7 to 10 days but some can last for up three weeks. symptoms may be more severe in infants,young children and tobacco users/smokers, and may include fiver and hives.

The common cold usually resolves spontaneously in 7 to 10 days but some symptoms can last for up to three weeks. There are no medications or herbal remedies proven to shorten the duration of illness. Treatment often is given via symptomatic supportive options, maximizing the comfort of the patient, and limiting complications and harmful sequelae.
The common cold is self-limiting, and the host's immune system effectively deals with the infection. Within a few days, the body's humoral immune response begins producing specific antibodies that can prevent the virus from infecting cells. Additionally, as part of the cell-mediated immune response, leukocytes destroy the virus through phagocytosis and destroy infected cells to prevent further viral replication. In healthy, immunocompetent individuals, the common cold resolves in seven days on average.

The National Institute of Allergy and Infectious Diseases suggests getting plenty of rest, drinking fluids to maintain hydration, gargling with warm salt water, using cough drops, throat sprays, or over-the-counter pain or cold medicines. Saline nasal drops may help alleviate congestion.
Treatment that may help alleviate symptoms include: analgesics, decongestants, and cough suppressants,[citation needed] first-generation anti-histamines such as brompheniramine, chlorpheniramine, diphenhydramine and clemastine (which reduce mucus gland secretion and thus combat blocked/runny noses but also may make the user drowsy). Second-generation anti-histamines do not have a useful effect on colds.

The best way to avoid a cold is to avoid close contact with existing sufferers; to wash hands thoroughly and regularly; and to avoid touching the eyes, nose, mouth, and face. Anti-bacterial soaps have no effect on the cold virus; it is the mechanical action of hand washing with the soap that removes the virus particles.
In 2002, the Centers for Disease Control and Prevention recommended alcohol-based hand gels as an effective method for reducing infectious viruses on the hands of health care workers. As with hand washing with soap and water, alcohol gels provide no residual protection from re-infection.
The common cold is caused by a large variety of viruses, which mutate quite frequently during reproduction, resulting in constantly changing virus strains. Thus, successful immunization is highly improbable.

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