Wikipedia
Sopona (or Shapona) is the god of smallpox in the Yoruba religion.
Within the traditional religion of the Yoruba people of Nigeria it is believed that smallpox was a disease foisted upon humans due to Shapona’s “divine displeasure”, and formal worship of the god of Smallpox was highly controlled by specific priests in charge of shrines to the god. Prior to the early 20th century people of this religion believed that if the priests were angered they were capable of causing smallpox outbreaks through their intimate relationship with Shapona. The name "Sapona" (alt. Shapona, Saponna, etc.) is considered a secret and taboo name, not to be spoken aloud in respect for the power of the Lord of Infectious Disease. For this reason, the deity has a number of other names and titles which have been in use since the pre-modern period, such as Omolu.
Sapona is the traditional, sacred and protected name of the Orisha popularly known as Babalú-Ayé or Omolu. Speaking his true name is avoided so as to not invoke the power of disease.
Dr. Oguntola Sapara suspected that the priests were deliberately spreading the disease, and surreptitiously joined the cult. He discovered that the priests were causing the disease through applying scrapings of the skin rash of smallpox cases. Based on this information, the British colonial rulers banned the worship of Shapona in 1907. Worship continues, however, with the faithful paying homage to the god even after such activities were prohibited.
Shapona was exported to the New World in the slave trade, where he has become known as Babalu Aye, among many other names, in the Orisha religion. Shakpana is an equivalent in Dahomey mythology.