The flu, or influenza (in-flu-EN-za), is an acute viral infection of the upper respiratory tract. Flu is caused by a virus that spreads from one person to another in the spray from coughs and sneezes, and more commonly from hand-to-hand contact. Early symptoms are chills, a high temperature, sneezing, headache, muscle pain, and a sore throat. These are usually followed by a hacking cough, and occasionally, chest pains. If there are no complications, you should recover within one to two weeks. However, weakness may persist for several weeks. Because flu is a viral infection, antibiotics aren't effective. But new drugs are being studied that can decrease the duration of symptoms, or possibly even prevent them. In the meantime, the best strategy is to get plenty of rest until your temperature returns to normal. Drink as much water or fruit juice as possible, and take aspirin or an aspirin substitute for aches and fever. In general, it's recommended that an aspirin substitute be given to children under the age of 16, in order to prevent Reye's (Rize) syndrome. In addition, if your fever persists for more than three to four days, call a physician. People who are at greatest risk from flu complications, such as infants, the elderly, and those chronic heart or lung disease, should get an annual flu vaccine. Because the virus changes from year to year, the vaccine must be updated each year, and cannot guarantee protection. For more information, contact a health care provider.