There are 23 species of tsetse fly that live in 4,000,000 square miles of sub-Saharan Africa, which they keep pretty much cattle free, courtesy of a disease they transmit called nagana. This, in turn, makes it possible for game animals to live in these areas, for which we must all be thankful.
Tsetses also transmit sleeping sickness, whose proper name is trypanosomiasis, and which, if left untreated, is 100 percent fatal, but if you catch it in time you can be cured of it. Only a small percentage of the flies carry it, so the chances of taking it home from a safari are scant to say the least. I’ve never known anyone who got it, or even heard of anyone, but plenty of people get malaria in Africa.