Ebola Haemorrhagic Fever
Ebola Hemorrhagic Fever is one of the most virulent viral diseases known to humankind, causing death in 50-90% of all clinically-ill cases. Consequently, it has figured prominently in popular discussions of biological warfare, although its practical applications as a biological warfare agent remain speculative. While all Ebola virus species have displayed the ability to be spread through airborne particles (aerosols) under research conditions, this type of spread has not been documented among humans in a real-world setting as of 2007. The disease has its origins in the jungles of Africa and Asia and several different forms of Ebola virus have been identified and may be associated with other clinical expressions.
Different hypotheses have been developed to try to uncover the cycle of Ebola. Initially, rodents were suspected, as is the case with Lassa Fever whose reservoir is a wild rodent (Mastomys). Another hypothesis is that a plant virus may have caused the infection of vertebrates. Insects may be another candidate. Laboratory observation has shown that bats experimentally infected with Ebola do not die and this has raised speculation that these mammals may play a role in maintaining the virus in the tropical forest.
History of Ebola
There are four types of Ebola: Ebola-Sudan, Ebola-Zaire, Ebola-Reston, and Ebola-Cote-d'Ivoire. A 30%-45% difference in nucleotides has been established between these strains.
The Ebola virus was first identified in a western equatorial province of Sudan. The outbreak began in the Nzara Cotton Manufacturing Factory and spread to the Nzara and Maridi areas of Sudan. Between June and November 1976 the Ebola virus infected 284 people in Sudan, with 53% mortality (117 deaths). That same year, an accident in a laboratory in England resulted in 1 non-fatal case of Ebola-Sudan. In 1979, another outbreak occurred in Nzara of Ebola-Sudan, and 65% of the 34 cases resulting in fatalities. Ebola-Sudan was again found in 2000-2001 in the Gulu, Masindi, and Mbarara districts of Uganda. Fatalities reached 53% of the 425 cases.
Closely following the outbreak in Sudan, Ebola surfaced in a nearby region of Zaire in 1976 after significant epidemics in Yambuku, northern Zaire, and Nzara, southern Sudan. This strain, known as Ebola-Zaire, is the most deadly of the four strains. The Yambuku case in 1976 proved deadly to 88% of the 318 cases (280 people). It began on September 1st with a 44-year-old male Mission school teacher who sought treatment for what he thought was a case of malaria at the Yambuku Mission Hospital. He received an injection of malaria medication, and the Ebola virus spread through medical equipment that was no sterilized. The hospital shut down on September 30th, and on October 18th, a World Health Organization Commission was formed. The last case died on November 5th. One case was discovered in Tandala, Zaire, in 1977. The next major outbreak of Ebola-Zaire was in Gabon in 1994 in the Mekouka and other gold-mining camps in the deep rain forests. The fatality rate was 59% (29 out of the 49 infected).
In 1995, a severe outbreak of Ebola-Zaire began in Kikwit, Zaire, beginning with a charcoal worker on January 6th. The disease spread by person-to-person contact and through ritual cleansings of the victims' bodies before burial. Of the 315 cases, there was a 77% case-fatality rate (244 dead). The outbreak officially ended on August 24th. In 1996, an outbreak in the Mayibout area of Gabon occurred following the ingestion of a dead chimpanzee found in the forest. The fatality rate was 68% of the 31 victims. A similar outbreak occurred in 1996 in the Booue area of Gabon that spread from a hunter who lived in a forest camp. 75% of the 60 cases resulted in fatalities. The virus was transported from Gabon to Johannesburg, South Africa, via a medical professional who had treated Ebola patients. While he recovered, a nurse who treated him died from the Ebola virus. In 2001-2002, an outbreak of the Ebola-Zaire strain occurred on the border area between Gabon and the Republic of the Congo. Of the 122 cases, there was a 79% fatality rate.
In 1989 and 1990, a filovirus, named Ebola-Reston, was isolated in monkeys being held in quarantine in a laboratory in Reston (Virginia), Alice (Texas) and Pennsylvania. Four humans developed antibodies without showing symptoms. In the Philippines, Ebola-Reston infections occurred in the quarantine area for monkeys intended for exportation, near Manila. A similar outbreak occurred in monkeys in 1996 in Texas and the Philippines. In 1992, Ebola-Reston virus was introduced into quarantine facilities in Sienna by monkeys imported from the same export facility in the Philippines that was involved in the episodes in the United States.
One human case of Ebola hemorrhagic fever and several cases in chimpanzees were confirmed in Côte d'Ivoire in 1994-95. A Swiss scientist became ill after conducting an autopsy on a wild chimpanzee in the Tai Forest, but the case did not result in a fatality.
Ebola as a Biological Weapons Agent
As a biological weapons agent, the Ebola virus is feared for its high case-fatality rate. Because of its rarity, the disease may not be diagnosed corrected at the onset of an outbreak. Reports suggested that the Ebola virus was researched and weaponized by the former Soviet Union's biological weapons program Biopreparat. Dr. Ken Alibek, former the First Deputy Director of Biopreparat, speculated that the Russians had aerosolized the Ebola virus for dissemination as a biological weapon. The Japanese terrorist group Aum Shinrikyo reportedly sent members to Zaire during an outbreak to harvest the virus.
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