Onchocerciasis, also known as river blindness, is a parasitic disease affecting the eyes and skin caused by the parasitic worm Onchocerca volvulus. Onchocerciasis is transmitted to humans through bites of infected blackflies. These blackflies are common in fast-flowing rivers and streams, typically in remote villages nearby fertile land used for agriculture. Symptoms of Onchocerciasis include severe itching, skin lesions, the development of nodules under the skin, and eye lesions that can lead to visual impairment and permanent blindness. This disease occurs primarily in tropical areas, with almost all of the infected people living in sub-Saharan Africa. Cases of this disease have also appeared in Yemen and Latin America. There is currently no vaccine or medication available to prevent infection.