Trypanosomiasis is a disease spread by the Tsetse Fly. These flies are dangerous and look almost exactly like regular houseflies. The World Health Organization thinks that they pose no benefit to humans, and drastically reducing their numbers would be a good thing since it would clearly result in decreased disease transmission.
One key difference between these flies and your regular merely annoying houseflies is their wings. Unlike the house fly the Tsetse Fly folds their wings in such a way that one wing rests directly on top of the other–I am sure that was helpful! So unless you are a junior entomologist who enjoys examining every fly you kill with a magnifying glass, you will probably not take notice of these particular flies.
These flies have been causing problems for a while, as they are extremely old, having been found in fossil beds in Colorado. Today their distribution is much more limited as they are only found in Africa south of the Sahara. So, if you are going on an African Safari watch yourself!
What do you know about the Tsetse fly? Have you ever traveled to a place where they pose a risk to humans? What did you have to do to protect yourself from them?