If influenza were an animal, it would be a chameleon. This program sheds light on the constantly changing virus, exploring medical efforts to track its adaptations, improve flu treatments, and develop a reliable vaccine. Explaining the differences between influenza types A, B, and C, the video describes how the body’s immune system reacts to an influenza attack, highlights the importance of T-cell levels, and looks at the particular vulnerability of people over age 65. Detailed commentary from physicians, researchers, and CDC authorities focuses on the historical cycle of epidemics and global pandemics and the push to develop an H5N1 avian influenza vaccine. (28 minutes)