Those most at risk are people who live in areas where the parasite is spread followed by adventure travelers, missionaries, and peace corps volunteers who are exposed for long periods of time (generally more than 3 months) to black fly bites in areas where the parasite exists. The disease is most intensely transmitted in remote rural African agricultural villages which are located near rapidly flowing streams.

The people most at risk for acquiring onchocerciasis are

• Those who live near streams or rivers where there are Simulium black flies. Most of the areas where the black flies are found are rural agricultural areas in sub-Saharan Africa.
• People who travel for short periods of time (generally less than 3 months) to areas where the parasite is found have a low chance of becoming infected with O. volvulus. Those travelers to at-risk areas most likely to become infected are
  • Long-term missionaries
  • Peace Corps and other long-term volunteers
  • Field researchers.