The U.S. Centers for Disease Control and Prevention reports that the ebola outbreak in West Africa is the largest ever documented.
As of June 23, there have been 635 confirmed Ebola cases and 399 deaths (case-fatality rate of 63%). The largest previous outbreak occurred in Uganda during 2000–2001, when 425 cases were reported with 224 deaths (case-fatality rate of 53%). The current outbreak is the first in West Africa and the first time that Ebola virus transmission has been reported in a capital city.
Ebola viral disease is characterized by the sudden onset of fever and malaise, myalgia, headache, vomiting, and diarrhea. Among EVD patients, 30% to 50% have hemorrhagic symptoms.
The first two Ebolavirus species were recognized in 1976 during simultaneous outbreaks in Sudan and Zaïre (now Democratic Republic of the Congo). Since 1976, there have been more than 20 EVD outbreaks across Central Africa, with the majority caused by Ebola virus (species Zaïre ebolavirus), which historically has demonstrated the highest case-fatality rate (up to 90%).
Read more from CDC.