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The flu
Definition:
The flu is a contagious infection of the nose, throat, and lungs caused by the influenza virus. Alternative Names:
Flu; Influenza A; Influenza B Text Continues Below
Causes, incidence, and risk factors:
The flu usually begins abruptly, with a fever between 102 to 106°F. (An adult typically has a lower fever than a child.) Other common symptoms include a flushed face, body aches, and lack of energy. Some people have dizziness or vomiting. The fever usually lasts for a day or two, but can last 5 days. Somewhere between day 2 and day 4 of the illness, the "whole body" symptoms begin to subside, and respiratory symptoms begin to increase. The flu virus can settle anywhere in the respiratory tract, producing symptoms of a cold, croup, sore throat, bronchiolitis, ear infection, or pneumonia. The most prominent of the respiratory symptoms is usually a dry, hacking cough. Most people also develop a sore throat and headache. Nasal discharge (runny nose) and sneezing are common. These symptoms (except the cough) usually disappear within 4-7 days. Sometimes, the fever returns. Cough and tiredness usually last for weeks after the rest of the illness is over. The flu usually arrives in the winter months. The most common way to catch the flu is by breathing in droplets from coughs or sneezes. Less often, it is spread when you touch a surface such as a faucet handle or phone that has the virus on it, and then touch your own mouth, nose, or eyes. Symptoms appear 1-7 days later (usually within 2-3 days). Because the flu spreads through the air and is very contagious, it often strikes a community all at once. This creates a cluster of school and work absences. Within 2 or 3 weeks of its arrival in a school, many student have become sick.
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