"H" is for Hookworm. In the early 1900s Charles W. Stiles identified a worm, Necator americanis, as the source of an infection that plagued the American South. Nurtured in damp soil, hookworm caused severe anemia, stunted growth, and often mental retardation in victims. What made Necator most threatening was its soaring infection rate (in parts of South Carolina it ranged as high as thirty-five percent). The starting point of infection was the lack of sanitary privies in most of the rural and mill village South--picked up by barefooted Southerners. The larvae pierced the victim’s skin; traveled to the small intestines where they developed into worms that “hooked” onto tissue and began a blood-feeding that could continue for years. Thanks the Rockefeller Sanitary Commission, by the 1940s hookworm was little more than a medical curiosity.