Ebola, formally known is Ebola hemorrhagic fever, is a severe and fatal disease that affects humans and non-human primates, such as monkeys, gorillas, and chimpanzees.  It first appeared sporadically in 1976.  The disease is attributable to the infection of the Ebola virus, which was named after a river in Congo, Africa where it was first observed.  This virus belongs to the Family Filoviridae, a group of RNA viruses.  Ebola Hemorrhagic Fever (EHF) usually appears in sporadic outbreaks, usually spread within a health-care setting. It is highly possible that sporadic, isolated cases occur, but go unrecognized.  EHF is one of the most virulent viral diseases known to humankind, causing death in 50-90% of all clinically ill cases.

The precise origin of Ebola is unknown, but is believed to live in the rain forests of Africa and Asia.  Several hypotheses have been presented to explain the natural origins, rather the natural reservoir of Ebola.  Scientists believe that the virus is zoonotic and is usually present in an animal host native to Africa or Asia. One hypothesis is that a wild rodent is the carrier of the deadly virus, as is the case with Lassa fever, a close relative of Filoviridae.  Other research speculates that a plant virus may have caused the infection of vertebrates.  Laboratory examinations have shown bats infected with the virus do not die; this raises the possibility that certain mammals are important in maintaining the virus in its tropical setting.

Non-human primates have been the source of human infections, but it is thought that they are not the natural reservoirs of this disease. Primates and humans are infected directly from the natural reservoir or via a chain of transmission from the natural reservoir; they do not contract the virus spontaneously.  Intense studies in Africa are hoping to yield the identity of the natural reservoir.

Members of Filoviridae are ranked among the deadliest viruses in existence.  The 1976 epidemics in Northern Zaire had a mortality rate of 88%; only HIV and rabies have recorded higher rates.  The disease kills within a week resulting from the severe bleeding and clotting.  Little is understood and known about Ebola, but researchers are hoping to find hope in Marburg, Ebola’s “sibling.”   The first recorded filovirus outbreak occurred in 1967 in Marburg, Germany.  A shipment of green monkeys infected 25 people who handled the monkeys.  The infection progressed into a severe hemorrhagic fever; six members of a medical staff and family members of the infected became infected after the initial outbreak.  Marburg began infecting again in 1975, killing one in Zimbabwe.

A new epidemic soon appeared one year later in Northern Zaire where it killed 280 people out of 318 infected.  This epidemic, however, was caused by a new strain of filovirus that was morphologically similar to Marburg but immunologically different.  Scientists dubbed it "Ebola" after a small river in Zaire where the first case is thought to have occurred.  It quickly spread because of close contact at hospitals, use of contaminated needles and syringes, and close contact during the burial process.

During the Zaire epidemic, Ebola was also making headlines in Southern Sudan.  No one could figure out how the two outbreaks occurred because there was no evidence of close contact between people from both places.  Ebola Sudan, however, had a lower mortality rate than Ebola Zaire.  The virus was not considered to be transmitted by airborne particles or droplets (WHO, 1978).  Single occurrences of Ebola and Marburg continued to appear sporadically between 1977 and 1987 mostly in Central Africa.  In 1989, a shipment of monkeys with destination to Reston, Virginia, became sick with a disease that resembled the symptoms of Simian Hemorrhagic Fever (SHF).  After this was observed, the monkeys were taken to the U.S. Army Medical Research Institute of Infectious Diseases (USAMRID).  Three of the ten monkeys tested positive for SHF.  Five of the monkeys tested positive for Ebola.  This was the first incidence of monkeys being naturally infected with the Ebola virus.  Monkeys stored in cages across the room became infected; these monkeys did not have any contact with the infected ones, so it is thought that the virus somehow became airborne.  Marburg and Ebola are quite infective at room temperature but are destroyed in 30 minutes when heated at 60 degrees Celsius. Infectivity is also destroyed by UV and gamma irradiation, lipid solvents, detergents, and common disinfectants (Peters, Sanchez, Feldmann, Rollin, Nichol, Ksiazkek, 1994; Peters, Jahrling, Ksiazek, Johnson, Lupton, 1992).