May 13, 1871: Smallpox epidemic breaks out in Cape Coast and surrounding territories

The first major smallpox epidemic broke out in Cape Coast and the interior. The Europeans had some immunity to this as it was endemic in Europe so adult survivors of childhood disease were often immune. The Asante Army which defeated the British and their coastal allies at Jukwa, 17 miles from Cape Coast, in 1873 under famed general Amankwa Tia, were eventually defeated by smallpox, which took a heavier toll on the non-immune Asante troops, causing their hasty withdrawal and turning the tide of history. Smallpox became a serious military liability to the Asante army often anywhere from 20,000 to 50,000 men in close quarters.

Further reading:

Philip D. Curtin, 1998 - Disease and Empire: The Health of European Troops in the conquest of Africa