Parasitic worm infections are a problem throughout low and middle-income countries in sub-Saharan Africa, South and East Asia, and some parts of Latin America and the Caribbean. Although illness caused by parasitic worms was once common in areas of high income countries, such as the United States, it has been eliminated through public health programs.

Soil-transmitted helminths (STH) can be found almost everywhere where inadequate water and sanitation conditions prevail. Schistosomes additionally require the presence of an intermediate snail host and are therefore most prevalent near water bodies where these snails can be found alongside poor water and sanitation conditions.

Children in almost all low and middle income countries are infected or at risk of becoming infected with STH. The conditions of poverty and poor sanitation increase the likelihood of being infected, and children, because of their hygiene and habits, are more likely to be infected.

For specific country information on the geographic distribution of STH and schistosomiasis, open access maps are available from the Global Atlas of Helminth Infection.