Common Cold

Common cold is a mild viral infectious disease of the upper respiratory system. Symptoms include sneezing, sniffling, runny nose, nasal congestion; scratchy, sore, or phlegmy throat; coughing; headache; and tiredness. Those affected may also feel achy. Colds typically last three to five days, with residual coughing and/or catarrh lasting up to three weeks. The common cold is the most common of all human diseases, infecting adults at an average rate of 2–4 infections per year, and school-aged children as many as 12 times per year. Infection rates greater than three infections per year per person are common in some populations. Children and their parents or caretakers are at a higher risk, possibly due to the high population density of schools and because transmission to family members is highly efficient.

The common cold belongs to the upper respiratory tract infections. It is different from influenza, a more severe viral infection of the respiratory tract that shows the additional symptoms of rapidly rising fever, chills, and body and muscle aches. While the common cold itself is rarely life-threatening, its complications, such as pneumonia, can be.

The viruses are transmitted from person to person in two ways. The most effective is by physical contact: a cold sufferer wipes his or her nose, shakes hands with someone who then rubs his or her eyes or nose. There is a lesser but significant level of infection from inhaling droplets from coughs or sneezes. Infective cold viruses can also persist on objects that have been handled, such as doorknobs and shopping carts, with a half-life of about one hour.

Between a third and a half of people exposed to a cold virus become infected; 75% show symptoms, which start 1-2 days after infection. Generally, a cold starts with a sore throat with no respiratory blockage. Later symptoms are a result of the body's defense mechanisms: sneezes, runny nose, and coughs. Coughs expel the invader while inflammation attracts and activates immune cells. Severe colds can even lead to a slightly stiff neck and mild to severe headaches with a slight fever for some.

Often confused with influenza, the common cold is caused by a different type of virus and usually does not result in a significantly higher body temperature. A high fever is a very reliable indicator of the flu.

After a common cold, a sufferer develops immunity to the particular virus. This immunity offers only limited protection against the many other cold viruses. The person, therefore, can easily be infected by a different cold virus.

...More at Wikipedia

Related Links:

• US National Library of Medicine
• Mayo Clinic

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