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Cough/ Cold/ Flu
Acute viral nasopharyngitis, often known as the common cold, is a mild viral infectious disease of the upper respiratory system (nose and throat). more...
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Symptoms include sneezing, sniffling, runny nose, nasal congestion; scratchy, sore, or phlegmy throat; coughing; headache; and tiredness. Colds typically last three to five days, with residual coughing lasting up to three weeks. It 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 not uncommon in some populations. Children and their parents or caretakers are at a higher risk, possibly due to the high population density of schools and the fact that 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 very well be.
Pathology
The common cold is caused by numerous viruses (mainly rhinoviruses, coronaviruses, and also certain echoviruses, paramyxoviruses, and coxsackieviruses) infecting the upper respiratory system. Several hundred cold-causing viruses have been described, and a virus can evolve to survive, ensuring that any cure is still a long way off. The nasopharynx is the central area infected. The reasons that the virus concentrates in the nasopharynx rather than the throat may be the low temperature and high concentration of cells with receptors needed by the virus.
Transmission
The viruses are transmitted from person to person by droplets from coughs or sneezes. The droplets or droplet nuclei are either inhaled directly, or transmitted from hand to hand via handshakes or objects such as door knobs, and then introduced to the nasal passages when the hand touches the nose or eyes.
The virus takes advantage of sneezes and coughs to infect the next person before it is defeated by the body's immune system. Sneezes expel a significantly larger concentration of virus \"cloud\" than coughing. The \"cloud\" is partly invisible and falls at a rate slow enough to last for hours—with part of the droplet nuclei evaporating and leaving much smaller and invisible \"droplet nuclei\" in the air. Droplets from turbulent sneezing or coughing or hand contact also can last for hours on surfaces, although less virus can be recovered from porous surfaces such as wood or paper towel than non-porous surfaces such as a metal bar. A sufferer is most infectious within the first three days of the illness. Symptoms, however, are not necessary for viral shedding or transmission, as a percentage of asymptomatic subjects exhibit viruses in nasal swabs, likely controlling the virus at concentrations too low for them to have symptoms.
Read more at Wikipedia.org
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