Rabies is the world's deadliest virus by fatality rate (100%), with 59,000 deaths per year, according to a post by Market Mind. It's followed by B Virus (80% fatality rate), Lujo Virus (80%), Nipah Virus (40-75%), Hendra Virus (57%), Ebola (50%) and Marburg Virus (50%). H5N1 (50%), CCHF (10-40%) and Mers-CoV (36%) are also in top 10.