What is influenza (flu)?
Influenza (flu) is an illness caused by a virus that comes on suddenly, and causes symptoms such as fever, body aches, headache, fatigue, loss of appetite, a dry cough, and a sore or dry throat. The flu is not the same as the common cold; flu symptoms are usually more severe, and you will often miss more work or school than you would with a cold.

Most people recover without problems, but sometimes the illness leads to a bacterial infection, such as an ear infection, sinus infection, or bronchitis.  Good home treatment may help prevent these infections. More serious complications, most commonly pneumonia, may develop in some people.  People at increased risk for complications that require hospitalization are young children, adults age 65 and older, and those with serious medical problems.

What causes the flu?
Influenza viruses A and B cause the classic flu. Type A is usually responsible for the outbreaks that occur annually.

These viruses are constantly changing, producing what are called subtypes or strains that are different from the original virus, but retain some of its characteristics. Strains of influenza virus that cause the flu may differ from year to year.

The flu causes fever, cough, shaking chills, body aches, headache and fatigue. These symptoms usually last for 3 to 4 days, after which you may have a dry cough, runny nose, and a sore or scratchy throat for another week or so. The incubation period - the time from exposure to the flu virus until you develop symptoms - is 1 to 4 days.

Although people often use the term "flu" to describe any kind of mild illness that has flu-like symptoms (such as the common cold or a stomach virus), the flu is a distinct viral illness with specific symptoms, and it tends to occur at a particular time of year - late fall and winter.

How is the flu diagnosed?
Health professionals usually can diagnose influenza using your symptoms alone, especially if many cases of a similar illness have occurred in the community and the local health department has confirmed a flu outbreak. Routine testing of people who have typical flu symptoms is usually not necessary. Rarely, the specific flu virus you have may be identified through a blood test or a nasal or throat swab.

How is it treated?
Home treatment is usually all that is needed for flu symptoms. However, antiviral medications are available to reduce the duration and severity of symptoms. These medications are especially useful for older adults and others who are at risk for developing complicdations from the flu. These medications need to be started within 2 days of your first symptoms. Talk to your doctor if you think you may need an antiviral medicine. Not all antiviral medicines work against all strains of the flu.

Can the flu be prevented?
You can help prevent the flu by getting immunized with an influenza vaccine each year, ideally in October or November. The standard vaccine, known as the "flu shot," is given by injection. It can be given after age 6 months to anyone who wishes to help prevent the flu. The flu shot is recommended for:

• All children age 6 months to 23 months.
• All adults age 50 and older.
• Adults and children age 2 and older who have health conditions such as asthma, chronic heart or lung disorders, or an impaired immune system.
• Women who will be pregnant during the flu season.
• Close contacts (including household members and health care workers) of anyone in a high-risk category, which includes all children 23 months of age and younger.

FluMist®, a live-virus vaccine in the form of a nasal spray, is an alternative to the flu shot that is now available for healthy children and adults between the ages of 5 and 49, except pregnant women. FluMist® should not be given to close contacts of people with severely impaired immune systems (such as those who have had a recent bone marrow transplant) to avoid their transmitting the virus after being vaccinated.

Other ways to reduce your risk of getting the flu or developing complications:
Increase your chance of staying healthy by:

• Washing your hands often, especially during winter months when the flu is most common.
• Keeping your hands away from your nose, eyes and mouth. Viruses are most likely to enter your body through these areas.
• Eating a healthy and balanced diet.
• Getting regular exercise.
• Not smoking. Smoking irritates the lining of your nose, sinuses, and lungs, which may make you susceptible to complications of the flu.