Influenza

The illness popularly known as the flu is one of the most common of the winter season. The word flu is short for the disease's full name, influenza. The disease is caused by a virus that invades the nose, throat, and lungs. In most cases, people who get the flu will recover in a week or so. In some instances, however, complications such as pneumonia can occur, leading to severe illness and even death.

How influenza is spread
In an infected person, the influenza virus lives in the tissue of the nose and lungs. When an infected person coughs or sneezes, tiny particles of the virus are released into the air, where they can be inhaled by another (uninfected) person. The virus quickly invades the tissues of the nose, migrating eventually to the throat and, finally, the lungs.

Influenza spreads quickly, especially in the winter, when many people are indoors. Because of this, an outbreak of influenza can quickly turn into an epidemic. Epidemics occur when large numbers of people are infected with the same disease within a short period of time. They can spread across cities, states, and continents, and they can even spread around the world. One of the worst epidemics of all time was the influenza epidemic of 1918–19. In one year, influenza killed more than 20 million people throughout the world. Other influenza epidemics have occurred since then, but none has been as deadly.

Symptoms
The initial symptoms, or signs of the disease, include body aches, chills, and fever. There may also be a sore throat and some coughing and sneezing. Patients often become extremely tired, and some may also experience sharp headache pain.

In some people—especially elderly people or very young children—infection with the influenza virus can lead to serious complications. These can include pneumonia and bronchitis, which are infections of the lungs or parts of the lungs. In some instances, infection with the influenza virus can lead to death.

Treatment
Treatment for influenza consists mainly of getting plenty of rest and drinking lots of fluids. Most people recover from a bout of influenza within one to two weeks. In the late 20th century, scientists developed medications that can treat influenza. However, in order for these medicines to work, they must be taken at the first sign of the disease. It is important to talk to a doctor about the illness and how it should be treated.

Children and teenagers should never use aspirin or aspirin-containing products to treat the headaches and body aches that accompany influenza. Using aspirin to treat influenza in children and teenagers has been connected to the development of a rare but serious illness called Reye syndrome.

Prevention
One of the best ways to avoid getting influenza is to be vaccinated against the influenza virus every year. Because the virus infects millions of people each year, getting vaccinated is also a good way to prevent the infection from spreading. For many diseases a single vaccine is all that is ever needed to protect against the virus. The influenza virus changes every year, however, so scientists must create new vaccines each year to protect against the new form of the virus.