Ebola viruses cause a severe and often deadly illness known as Ebola virus disease (EVD, also referred to as Ebola hemorrhagic fever). Fatality rates during EVD outbreaks can be as high as 90 percent. Ebola viruses produce hemorrhagic fever, a condition that also can be brought about by other types of viruses but Ebola produces one of the most lethal forms. In addition to the other symptoms of hemorrhagic fever – fever, headache, aches, weakness, vomiting, and diarrhea – the more severe cases can include damage to blood vessels and extensive internal and external bleeding (hemorrhage). Mortality rates for EVD range from 50 percent to 90 percent, with death usually occurring as a result of shock rather than blood loss. The virus is transmitted through direct contact with blood or other body fluids of infected persons or animals, including close contact with deceased Ebola-infected patients.