Situation and trends
Soil-transmitted helminth infections are among the most common infections worldwide and affect the poorest and most deprived communities. They are transmitted by eggs present in human faeces which in turn contaminate soil in areas where sanitation is poor. The main species that infect people are the roundworm (Ascaris lumbricoides), the whipworm (Trichuris trichiura) and the hookworms (Necator americanus and Ancylostoma duodenale). Soil-transmitted helminth infections are widely distributed in all WHO Regions. For the control of these infections, WHO recommends the periodic administration of anthelminthic medicines (albendazole or mebendazole) as a public health intervention, for children (from 1 to 15 years of age) living in areas where the prevalence of STH is estimated to be over 20%. According to WHO estimates about 875 million children worldwide require preventive chemotherapy for soil-transmitted helminthiases. In 2011 more than 267 million children in need of treatment received preventive chemotherapy for STH, corresponding to 30.6% global coverage. In 2011, 21 countries have reached the World Health Assembly's target of treating at least 75% of school-aged children for the disease.