Dr. Oguntola Sapara suspected skulduggery from the influential priests of Sopona, the Yoruba god of smallpox. He was right.
Oguntola Sapara was born in Sierra Leone but his family moved to Lagos in 1876, when Sapara was a teenager. He trained as a doctor in London, worked in Scotland, and then returned to Nigeria in 1896. Over the next three decades he fought outbreaks of tuberculosis and bubonic plague, trained midwives, and improved public health throughout the country.
His most famous battle, though, was against a secret society: the priests of Sopona. In the Yoruba religion, Sopona (also known as Shapona) was the god of smallpox. People believed that if you displeased the god then you may be struck down with the disease. In 1897 Sapara was appointed to the town of Epe, which was a hotbed of smallpox cases. He noted that the usual preventative measures and vaccinations didn’t seem to help, and he also noted that the local priests of Sopona were very influential (unsurprising, given the number of cases!).
Sapara was suspicious, but he needed proof. So he joined the cult. Having infiltrated their ranks, he discovered that the priests were purposefully infecting people to increase their power and control. They were taking skin scrapings from poxy patients and spreading them to others, and blackmailing people with their god’s wrath.
Sapara ran the priests out of town under threat of prosecution, and then alerted the British authorities. In 1907, worship of the smallpox god was banned throughout the country. It of course continued in secret, and smallpox outbreaks continued in Nigeria until the 1960s, but by 1977 the disease was extinct in the wild thanks to the efforts of doctors like Oguntola Sapara.