A-Z Health Topics Index

Flu—Get the Shot
Each winter, millions of people suffer from seasonal flu. Flu—the short name for influenza—is caused by viruses. Viruses are very small germs. Some viruses can spread easily from one person to another. They cause illnesses or infections like the flu. Flu is a mild illness for some people. For older people, especially those who have health problems like diabetes or heart disease, the flu can be very serious, even life-threatening.