Going barefoot in parts of Africa, Asia and South America is dangerous.
Hookworms live in the soil and enter the body through the feet. By feeding on victims' blood, the worms cause anemia and, in children, stunted growth and learning problems. These infections afflict an estimated 700 million of the world's poor.
Researchers have decoded the genome of the hookworm, Necator americanus, finding clues to how it infects and survives in humans. Necator americanus causes about 85 percent of human hookworm infections, which are not usually fatal. However, in pregnant women, the worm can cause severe anemia, leading to maternal deaths and low birth weights that contribute to newborn deaths.