Two million people have severely impaired vision and 350,000 are totally blind. 18 million are infected with River Blindness and a further 80 million are at risk. The disease is most prevalent in Africa. It is caused by parasitic worms, which are spread by the bite of the black simulium fly. It causes years of suffering, including severe itching and debilitation, before invading the eye and leading slowly to permanent blindness. It blinds young adults when they should be at their most economically productive.

An annual dose of Mectizan® kills the minute offspring of the parasitic worms which cause the damage. It must be taken for over ten years to break the transmission cycle of the disease.