There are more than 6,500 identified rare and neglected diseases, yet only about 250 treatments are available for these conditions. One reason is that limited numbers of patients can make gathering information and designing drug studies difficult. As a result, scientists often know little about the symptoms and biology of these conditions. Another obstacle is that some private companies may find it difficult to justify the cost of developing drugs for such small rare disease markets. Even in the case of infectious diseases — such as malaria — that inflict health burdens on large numbers of people in the developing world, the private sector often neglects therapeutic development because of insufficient economic incentives. Learn more about TRND.