Rabies causes viral encephalitis which kills up to 70,000 people/year worldwide. Infected animal saliva transmits viral encephalitis to humans. Rabies is one of the oldest known diseases in history with cases dating back to 4000 years ago. For most of human history, a bite from a rabid animal was uniformly fatal. In the past, people were so scared of rabies that after being bitten by a potentially rabid animal, many would commit suicide. Pasteur's rabies vaccine from 1885 has led to such intense prophylaxis in developed countries, that in the United States, for example, there have only been about two rabies deaths per year for the past two decades; less developed countries are not so lucky.