Approximately two billion people, or almost 29% of the world's population are infected with soil-transmitted helminth (parasitic worms) infections worldwide. These are transmitted to people through contaminated soil and affect the poorest and most deprived communities. The main species of soil-transmitted helminths that infect people are the roundworm (Ascaris lumbricoides), the whipworm (Trichuris trichiura) and the hookworms (Necator americanus and Ancylostoma duodenale). Such infections are widely distributed in tropical and subtropical areas, with the greatest numbers occurring in sub-Saharan Africa, the Americas, China and east Asia. Over 270 million preschool-age children and over 600 million school-age children live in areas where these parasites are intensively transmitted, and are in need of treatment and preventive interventions.Source: World Health Organization Media centre (Fact sheet No. 366, June 2012)
