According to the most recent estimates, there are almost a billion men, women, and children infected with hookworm. Among the most affected peoples in the world are the poorest populations in sub-Saharan Africa, the Americas, and Asia. For centuries, hookworm has been a major problem among the Chinese. According to Peter Hotez, between 1990 and 1992, parasitologists in various parts of China undertook what I consider to be one of the most intense surveys of the problem ever conducted. They collected more that 1.4 million stool samples from 2848 study sites in 726 counties in every province in the country. Of these, 17% passed eggs of either Necator americanus or Ancylostoma duodenale. This extrapolates to approximately 194 million cases of hookworm disease in just that country, and it does not include those who have had the disease and lost it for one reason or another. The enormity of the problem is exacerbated by Norman Stoll's estimate in 1962 that each day hookworms suck enough blood to cause the total exsanguination of 1.5 million people. The number of infections by hookworm has nearly doubled since the publication of Stoll's paper, so we can safely assume the amount of blood lost on a daily basis has, likewise, doubled!

Hookworm disease has been associated with humans since we changed from being hunter-gatherers to farmers.