Usually, plague is a disease of rodents, but when an outbreak reduces the rodent population in the vicinity of human habitation fleas from the dead animals are unable to find another rodent host and begin to infest man. In Zambia, infected dead rats have been found in boreholes and in water drawn from wells. Flooding had forced them from their normal habitats to human settlements. The illness in man varies from mere indisposition to violent death. The temperature rises rapidly but then falls two or three degrees on the second or third day, with marked prostration.
Constipation is usual but diarrhoea occurs in severe cases.
The disease gets its name from the black swellings that appear in the groin and armpits. Bubonic plague, unlike the other two forms, is not directly infectious from man to man and is transmitted only by fleas. The clinical diagnosis was established by the South West Regional Office and confirmed by a team of experts from the University Teaching Hospital in Lusaka. According to the World Health Organisation, a total of 267 cases have been reported in Namwala District in the Southern Province and 25 patients are still under treatment. Namwala entry and exit points now have medical personnel manning them to prevent spread of the disease.