With the Ebola viruses it can be noted that the virus is found in high concentrations in tissues throughout the body and are especially evident in the liver, spleen, and skin. To see a picture of an actual Ebola virus strand, see attachment 1. From studies of human cases and experimentally infected animals, it appears that the immune response is impaired and that a strong cellular immune response is key to surviving infections. This immune suppression may also factor in death, especially if secondary infections by normal bacteria ensue which is much how the AIDS virus works.
The Ebola virus causes hemorrhagic fever, which is characterized by such symptoms as severe headache, weakness, and muscle aches, followed by vomiting, abdominal pain, diarrhea, inflammation of the throat (pharyngitis), inflammation of the mucous membranes in the eye (conjunctivitis), bleeding from body openings, and, often, destruction of internal tissues. Rapid viral replication in infected cells is the direct cause of cell and tissue destruction. The onset of illness is sudden, and the disease often progresses swiftly to extreme exhaustion (prostration), dehydration, and death. The time from exposure to the onset of illness is usually five to ten days, and the time from onset of illness until death or improvement is usually seven to ten days. The mortality rates in the known outbreaks have been 60 percent with Ebola/Sudan virus and 77 to 88 percent with Ebola/Zaire virus.
Each outbreak has been traced to an index case, an infected person who was exposed to a reservoir host, an animal or arthropod involved in the life cycle of the virus. Of all the disease-causing human viruses, the Ebola and its relative Marburg, which also causes hemorrhagic fever, are the only ones remaining for which the host and the natural transmission cycle remain unknown. It is not known whether monkeys serve as hosts or if other mammals, birds, reptiles, or even mosquitoes or ticks are involved.
