How can we compare the Plague of Justinian, which ravaged the Mediterranean basin in the 6th century, with AIDS, which emerged in the 1980s? Despite their differences, cholera, syphilis, leprosy, and smallpox all share a common trait: they are pandemics that spread quickly and strike hard. How can we combat these invisible scourges? In this inquiry, Patrick Berche and Stanis Perez trace the global histories of major diseases, from prehistoric times to COVID-19, combining scientific rigor with a critical look at our contemporary health challenges.