What is influenza?

a diagram of the flu symptoms

Influenza, or "the flu," is a highly contagious viral disease that infects noses, lungs, and windpipes, spreading through droplets in the air when an infected person coughs, sneezes, or speaks. (Germs can also linger on surfaces.) New strains appear constantly, spreading mostly during the flu season that runs from November through May here in the US. Each year, influenza strikes some 200,000 Americans, killing 36,000 people annually and sending many more to the hospital.

One to five days after infection, sufferers develop fever, headache, muscle aches, fatigue, cough, sore throat, and runny or stuffy nose. (People sick with the 2009 H1N1 flu virus have also reported vomiting and diarrhea.) Most people recover completely in one to two weeks, but some develop life-threatening complications such as pneumonia.

What to do if you catch the flu?

If you develop flu symptoms, stay home! (You're contagious until 7 days after your symptoms begin.) Get plenty of rest, drink lots of clear fluids, avoid close contact with others, and practice good hygiene: wash your hands frequently, and cover coughs and sneezes. Know the emergency warning signs that indicate you might need to see a doctor.

If you're really, really sick or at high risk for complications (over 65 years old, under 5 years old, pregnant, or have a chronic health problem or a weakened immune system), a doctor can prescribe antiviral medicines—Tamiflu (oseltamivir) and Relenza (zanamivir)—to help relieve your symptoms.