From the text:The Ebolas were named Ebola Zaire and Ebola Sudan. Marburg was the mildest of the three filovirus sisters. The worst of them was Ebola Zaire. The kill rate in humans infected with Ebola Zaire is nine out of ten. Ninety percent of the people who come down with Ebola Zaire die of it. Ebola Zaire is a slate wiper in humans.
Preston, Richard (2012-03-14). The Hot Zone: The Terrifying True Story of the Origins of the Ebola Virus (p. 36). Knopf Doubleday Publishing Group. Kindle Edition.