In the late eighteenth century, yellow fever was widespread in the Caribbean; case-fatality rates among British troops there were as high as 70 percent. The fate of French troops sent to Saint-Domingue to suppress a slave rebellion was even worse. “Evidence suggests the troops were actually an expeditionary force with intentions to invade North America through New Orleans and to establish a major holding in the Mississippi valley,” wrote the authors of a 2013 scholarly paper. Mortality from the disease thwarted Napoleon’s “secret ambition to colonize and hold French-held lands, which later became better known as the Louisiana Purchase.”

In 1942 a contaminated yellow-fever vaccine caused an outbreak of hepatitis B among more than 300,000 U.S. Army and Allied troops. Nearly 50,000 clinical cases resulted from the contamination, including 29,000 incidents of overt jaundice. There had been medical evidence of postvaccination epidemics of hepatitis in both men and horses since 1885.

Around 1500 bc, the Hittite augur Maddunani sacrificed to the gods one goat kid, one piglet, and one puppy in an attempt to end an epidemic that had devastated the army. While puppies played “an extensive, and apparently vital” role in Hittite ritual, wrote historian Billie Jean Collins, “this is the only case in Hittite ritual of puppies being killed as an offering.”