The Quiet Worm Plague

Schistosomiasis infects hundreds of millions of people with blood flukes that can live inside the veins for decades. Hookworms infect hundreds of millions more, latching onto the gut wall and drinking blood until severe anemia sets in.

In the early 1900s, hookworm was so common in the American South that it helped create the cruel stereotype of the "lazy Southerner." Those people were not lazy. They were anemic, drained of energy by worms feeding on their blood.