Your body is under attack every minute of every hour of every day. The enemy is patient, adaptable, potentially deadly, and invisible. Called the "littlest assassins" and "phantom killers," viruses range from the common cold to HIV and have caused epidemics more devastating than war. This video explains how viruses operate and how your immune system defends you. And it shows scientists turning the tables, transforming invading viruses into agents of healing. Produced by Discovery Channel School. © 1997 Discovery Channel School
