Bats are known to be carriers of diseases that can be transmitted to humans. One of the most common diseases that bats carry is called rabies. Rabies is a virus that affects the nervous system of mammals, including humans. It can be transmitted through the saliva of infected animals, usually through a bite. If left untreated, rabies can be fatal. In fact, more than 60% of all rabies cases in the United States are attributed to bats.