A zoonotic disease caused by bacteria known as Yersinia pestis. It is a disease of rodents, but accidentally can be transmitted to human being by fleas from infected rodents. The earliest cases of human plague epidemics were recorded towards the end of the 19th and the beginning of the 20th Century.

Sporadic cases of plague were experienced in Lushoto since 1980 and Karatu in 1996. However plague elapsed in Mbulu in 2007. Currently, there are three active foci in the districts of Lushoto (Tanga), Karatu (Arusha) and Mbulu (Manyara). Overall, the disease has affected about 9,000 people and has resulted into 700 deaths.