In the districts neighbouring the Serengeti National Park rabies, mostly spread by domestic dogs, causes about 50 human deaths each year. The disease can also be transmitted to wildlife, and is a particular risk for wild dogs as their social nature makes epidemics more likely. It is suspected that rabies infection contributed to the disappearance of wild dogs from the Serengeti in the early 1990s. They have now begun to recolonize the area, but the disease still represents an imminent threat to their survival.