Ebola - The virus - Encyclopedia II

The virus comes from the Filoviridae family, of which Marburg virus is also a member. It is named after the Ebola River in the Democratic Republic of the Congo (formerly Zaire), near the first epidemics.

It is traditional to name viral species (strains, subtypes) after the locations where they were first discovered. Two species were identified in 1976: Zaire ebolavirus (ZEBOV) and Sudan ebolavirus (SEBOV) with case fatality rates of 83% and 54% respectively. A third species, Reston ebolavirus (REBOV), was discovered in November 1989 in a group of monkeys (Macaca fascicularis) imported from the Philippines to the Hazleton Primate Quarantine Unit in Reston, Virginia (USA).

Further outbreaks have occurred in Zaire/Democratic Republic of the Congo (1995 and 2003), Gabon (1994, 1995 and 1996), Uganda (2000), and Sudan again (2004). A new species was identified from a single human case in Côte d'Ivoire in 1994, Ivory Coast ebolavirus (ICEBOV). In 2003, 120 people died in Etoumbi, Republic of Congo, which has been the site of four recent outbreaks, including one in May 2005.

Of the approximate 1,500 identified Ebola cases worldwide, over 80% of the patients have died. Despite considerable effort by the World Health Organization, no animal or arthropod reservoir capable of sustaining the virus between outbreaks has been identified, although a role for fruit or insectivorous bats is often postulated. BBC News reported that researchers writing in the December 1, 2005, issue of Nature had identified evidence of symptomless Ebola infection in three species of fruit bats from the Democratic Republic of Congo and Gabon.

Zaire ebolavirus, the first-discovered Ebola virus species, is also the most deadly with up to a 90% mortality rate in some epidemics. There have been more outbreaks of Zaire ebolavirus than any other strain. The first outbreak took place on August 26, 1976 in Yambuku, a town in northern Zaire (now the Democratic Republic of the Congo). The first recorded case (not the index case) was a Mabalo Lokela, a 44 year old school teacher just returning from a trip around Northern Zaire, who was examined at a hospital run by Belgian nuns. His high fever was diagnosed as possible malaria, therefore he was given a quinine shot. Lokela returned to the hospital every day. A week later, his symptoms included uncontrolled vomiting, severe diarrhea, headache, dizziness, and trouble breathing. Later, the bleeding began from his nose, mouth, and rectum. Mabalo Lokela died on September 8, 1976, roughly 14 days after the onset of symptoms.

Soon after, more patients arrived with varying but similar symptoms: fever, headache, muscle/joint aches, fatigue, nausea, dizziness etc. which often progressed to bloody diarrhea, severe vomiting, and bleeding from the nose, mouth, and rectum. The initial transmission was believed to be due to reuse of the needle for Lokelas's injection without sterilization (a common practice in many countries). Subsequent transmission was also due to care of the sick patients without barrier nursing and traditional burial preparations, which involves washing and GI tract cleansing.

A similar case of hospital transmission occured in southern Sudan, after the death of a nightclub owner in Nzara who could afford to go to the fancier hospital located in Maridi. Unfortunately, the nurses there also did not properly sterilize their needles, and the hospital, like the one in Yambuku, became a breeding ground for new Ebola cases (Draper 30–31). Several epidemics of Zaire ebolavirus and Sudan ebolavirus have occurred since 1976.

The case fatality rates were 88% in 1976, 100% in 1977, 59% in 1994, 81% in 1995, 73% in 1996, 80% in 2001/2002 and 90% in 2003. The average case fatality rate for Ebola Zaire is 82.6%.

The most recent outbreak of Sudan ebolavirus occurred in May 2004. As of May 24, 2004, 20 cases of Sudan ebolavirus (including five deaths) were reported in Yambio County, Sudan. The Centers for Disease Control and Prevention confirmed the virus a few days later. The neighboring countries of Uganda and the Democratic Republic of Congo have increased surveillance in bordering areas, and other similar measures have been taken to control the outbreak.

The average fatality rates for Sudan ebolavirus were 53% in 1976, 68% in 1979, and 53% in 2000/2001. The average case fatality rate is 53.76%.

This species was discovered in November of 1989 in a group of 100 cynomolgus macaques (Macaca fascicularis) imported from Ferlite Farms in Mindanao, Philippines to Hazleton Research Products Primate Quarantine Unit in Reston, Virginia, about 10 miles from Washington, D.C. A parallel infected shipment was also sent to Philadelphia, Pennsylvania. This strain was highly lethal in monkeys, but did not cause any illness in humans. Six of the Reston primate handlers tested positive (2 due to previous exposure) for the virus, but none became ill. Further Reston ebolavirus infected monkeys were shipped to Hazleton (now known as Covance, Inc.) facilities in both Reston, Virginia and Alice, Texas (Hazleton's Texas Primate Center) in February of 1990. This strain was also found to be airborne. More Reston ebolavirus infected monkeys were discovered in 1992 in Siena, Italy and at the Texas Hazleton facility again in March 1996. There was a high rate of co-infection with Simian Hemorrhagic Fever (SHF) in all of these Reston ebolavirus infected monkeys. No human illness has resulted from any of these outbreaks. The Reston virus was confusing to members of both USAMRIID and the CDC, who worked on eliminating the virus. See Ebola Reston for more information.

In 1994, a scientist became ill after conducting a necropsy on a wild chimpanzee. The scientist recovered,⁶ however, there is still little known about this species of Ebola virus since only this single case has been identified.

Adapted from the Wikipedia article "The virus", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki/Main_Page