Flu, influenza, the bug.  No matter what name it goes by, the result is the same.  Misery in the form of fever, coughing, body aches, headache, and fatigue.

Anyone can get the flu.  In fact, about 35 million Americans do every year.  Most will fully recover in a week or two, but some people develop life-threatening complications like pneumonia.  According to the Centers for Disease Control, in an average year roughly 114,000 people suffer complications from the flu that result in hospitalization, and as many as 36,000 people die.

Complications can happen to people of any age.  Those with chronic medical conditions, people age 65 years and older and very young children are most at risk.

There's no cure for the flu.  In some cases, antiviral medications can reduce the severity and shorten the duration of flu symptoms by one or two days if taken within 48 hours of the onset of symptoms.  These medications may also be used to control outbreaks and prevent the spread of infection, especially in people who can't be given flu vaccine but are at high risk for developing complications.   Most people simply drink plenty of water get plenty of rest and take pain relievers or cough medications to relieve symptoms.

Although people often use the term "flu" to describe any kind of mild illness that has flu-like symptoms, the seasonal or common flu is a distinct viral illness with specific symptoms, and it tends to occur at a particular time of year-late fall and winter in the Northern Hemisphere.

Flu vaccines have helped to make flu epidemics much less serious. They work about 70 to 90 percent of the time in healthy adults, either preventing the flu or making symptoms less severe.  In elderly or chronically ill people, the flu vaccine may be less effective in preventing illness than it is in preventing serious complications and death.  Since flu viruses change form every year, new vaccines are produced to combat whatever strains are anticipated.   

You may have heard the terms pandemic flu and avian flu (also called "bird flu"). 
Seasonal flu, pandemic flu and avian flu are not the same. 

Outbreaks of seasonal flu follow predictable seasonal patterns.  It occurs annually, usually in winter, in temperate climates. 

A pandemic is a global disease outbreak. A flu pandemic occurs when a new form of the flu emerges for which people have little or no immunity.  This new form of the flu often spreads rapidly and is usually resistant to any flu vaccines developed in the past.  See the U.S. Department of Health and Human Services article, "How Does Seasonal Flu Differ From Pandemic Flu?"  for more information.

Avian flu is a unique strain of flu.  It is a type of flu virus that occurs naturally among wild birds, but domesticated birds may become infected through direct contact with infected birds or through contact with surfaces or materials that have been contaminated with the virus.  Normally it is not spread to humans.  However, on occasion, a virus subtype develops the ability to cross the species barrier.  That's what happened to cause the recent outbreak of avian flu in humans.  And it has been one of the most deadly to cross the barrier with symptoms that have included severe respiratory distress, pneumonia and other life threatening complications.  See the U.S. Department of Health and Human Services "Fact Sheet on Avian Flu" for more information.