For over a hundred years, millions of Americans have joined together to fight a common enemy by campaigning against diseases. In Common Enemies, Rachel Kahn Best asks why disease campaigns have dominated a century of American philanthropy and health policy and how the fixation on diseases shapes efforts to improve lives. Combining quantitative and qualitative analyses in an unprecedented history of disease politics, Best shows that to achieve consensus, disease campaigns tend to neglect stigmatized diseases and avoid controversial goals. But despite their limitations, disease campaigns do not crowd out efforts to solve other problems. Instead, they teach Americans to give and volunteer and build up public health infrastructure, bringing us together to solve problems and improve our lives.