While quarantine was a staple of public health efforts for centuries to combat such scourges as the plague and the Spanish flu, with the advent of vaccines, antibiotics, and new treatments in the twentieth century, public health practitioners increasingly viewed quarantine as a regressive and backward approach. These revolutionary technologies effectively put an end to diseases that had once killed or maimed millions, such as polio and smallpox—leading to a new optimism among medical scientists that society might one day be rid of infectious diseases. As chronic illness replaced infectious disease as the leading cause of death in the twentieth century, public health came to view individual health behaviors—such as smoking and diet—as the primary cause of disease. Under this new individualism, smokers and the obese became the new Typhoid Mary. To control these modern health threats, public health devised new strategies, such as health marketing and education. But the volatile politics of AIDS threatened to turn back the clock on public health practice, as conservatives demanded that HIV-positive people be quarantined—or worse.