NTDs are a group of tropical infections which are especially endemic in low-income populations in developing regions of Africa, Asia, and the Americas. Different organizations define the set of diseases differently. In sub-Saharan Africa, the impact of these diseases as a group is comparable to malaria and tuberculosis. Some of these diseases have known preventive measures or acute medical treatments which are available in the developed world but which are not universally available in poorer areas. In some cases, the treatments are relatively inexpensive. For example, the treatment for schistosomiasis is USD $0.20 per child per year. Nevertheless, control of neglected diseases is estimated to require funding of between US$2 billion to US$3 billion over the next five to seven years.
These diseases are contrasted with the big three diseases (HIV/AIDS, tuberculosis, and malaria), which generally receive greater treatment and research funding. The neglected diseases can also make HIV/AIDS and tuberculosis more deadly. However, some pharmaceutical companies have committed to donating all the drug therapies required and mass drug administration has been successfully accomplished in several countries. Neglected tropical diseases include, in order of decreasing prevalence: