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Template:Taxobox begin Template:Taxobox image Template:Taxobox begin placement virus Template:Taxobox group v entry Template:Taxobox ordo entry Template:Taxobox familia entry Template:Taxobox genus entry Template:Taxobox end placement Template:Taxobox section subdivision Ivory Coast ebolavirus
Reston ebolavirus
Sudan ebolavirus
Zaire ebolavirus Template:Taxobox end Ebola is a virus of the Filoviridae family which causes Ebola hemorrhagic fever, a fatal disease in humans.

The virus

The virus comes from the Filoviridae family, of which Marburg virus is also a member. The natural host of the virus, probably an animal that can carry the virus without experiencing symptoms of infection, is unknown. Two candidate vectors are fruit bats and non-human primates. The Ebola virus 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 Ebola virus (ZEBOV) and Sudan Ebola virus (SEBOV) with case fatality rates of 83% and 54% respectively. A third species, Reston Ebola virus (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), Angola (2005) and Sudan again (2004). A new species was identified from a single human case in Côte d'Ivoire in 1994, at first named Ivory Coast ebolavirus (ICEBOV) and later changed to Tai Forest ebolavirus (TFEBOV) at an unknown time. 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.

A potential outbreak occurred on May 19, 2006 when a woman traveling from Africa to London complained initially of flu-like symptoms. On the flight she began vomiting and later died from symptoms similar to Ebola. An autopsy to determine true cause of death is currently being performed. [1]

Zaire Ebola virus

Zaire Ebola virus, is a non-segmented, negative stranded virus and is one of the first-discovered Ebola virus species. It is also the most deadly with up to a 90% mortality rate in some epidemics. There have been more outbreaks of Zaire Ebola virus 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 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, bloody diarrhea, headache, dizziness, and trouble breathing. Later, he began bleeding 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. 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 occurred in southern Sudan, after the death of a nightclub owner in Nzara who could afford to go to the better equipped 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%.

A graphical representation of known human cases and deaths during outbreaks of Zaire ebolavirus between 1976 and 2003.


Sudan Ebola virus

The most recent outbreak of Sudan Ebola virus 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 Ebola virus were 53% in 1976, 68% in 1979, and 53% in 2000/2001. The average case fatality rate is 53.76%.

A graphical representation of known human cases and deaths during outbreaks of Sudan ebolavirus between 1976 and 2003.


Reston Ebola virus

Main article: Ebola Reston

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 fatalities in humans. Six of the Reston primate handlers tested positive (two due to previous exposure) for the virus, and exhibited severe flu-like symptoms. 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 Ebola virus 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 Ebola virus infected monkeys. No human illness has resulted from these two outbreaks. The Reston virus was confusing to members of both USAMRIID and the CDC, who worked on eliminating the virus.

Symptoms

Symptoms are varied and often appear suddenly. Initial symptoms include: high fever (at least 38.8° C, 101° F), severe headache, muscle/joint/abdominal pain, severe weakness and exhaustion, sore throat, nausea, and dizziness. Before an epidemic is suspected, these early symptoms are easily mistaken for malaria, typhoid fever, dysentery, or various bacterial infections, which are all far more common. The secondary symptoms often involve bleeding both internally and externally from any opening in the body: Dark or bloody stools and diarrhea, vomiting blood, red eyes from swollen blood vessels, red spots on the skin from subcutaneous bleeding, and bleeding from the nose, mouth, rectum, genitals and needle puncture sites. Other secondary symptoms include low blood pressure (less than 90mm Hg) and a fast but weak pulse, eventual organ damage including the kidney and liver by co-localized necrosis, and proteinuria (the presence of proteins in urine). The span of time from onset of symptoms to death (from shock due to blood loss and/or organ failure) is usually between 7 and 14 days.

Transmission

Among humans, the virus is transmitted by direct contact with infected body fluids. The incubation period is 2 to 21 days.

Although airborne transmission between monkeys has been demonstrated in a laboratory (see below), there is very limited evidence for human-to-human airborne transmission in any reported epidemics.16,17,18 Nurse Mayinga may represent the only possible case. The means by which she contracted the virus remain uncertain.

So far all epidemics of Ebola have occurred in sub-optimal hospital conditions, where practices of basic hygiene and sanitation are often either luxuries or unknown to caretakers and where disposable needles and autoclaves are unavailable or too expensive. In modern hospitals with disposable needles and knowledge of basic hygiene and barrier nursing techniques (mask, gown, gloves), Ebola rarely spreads on such a large scale.

In the early stages, Ebola may not be highly contagious. Contact with someone in early stages may not even transmit the disease. As the illness progresses, bodily fluids from diarrhea, vomiting, and bleeding represent an extreme biohazard. Due to lack of proper equipment and hygienic practices, large scale epidemics occur mostly in poor, isolated areas without modern hospitals and/or well-educated medical staff. Many areas where the infectious reservoir exists have just these characteristics. In such environments all that can be done is to immediately cease all needle sharing or use without adequate sterilization procedures, to isolate patients, and to observe strict barrier nursing procedures with the use of a N95/P95/P100 or medical rated disposable face mask, gloves, (if possible) goggles, and gown at all times. This should be strictly enforced for all medical personnel and visitors.

Vaccines

Vaccines were recently produced for both Ebola and Marburg that were 100% effective in protecting a group of monkeys from the disease.1,15 Recent tests were conducted at USAMRIID in collaboration with Canada's National Microbiology Laboratory in Winnipeg. A Dutch company, Crucell, has also announced a successful test of their commercial vaccine in monkeys. No human testing has yet been announced for any of these filovirus vaccines. Earlier vaccine efforts, like the one at NIAID in 2003 that was entering human trials have so far not reported any successes.14

Treatments

Despite some initial anecdotal evidence to the contrary, blood serum from Ebola survivors has been shown to be ineffective in treating the virus.

In 1999, Maurice Iwu announced at the International Botanical Congress that a fruit extract of Garcinia kola, a West African tree long used by local traditional healers for other illnesses, stopped Ebola virus replication in lab tests. It is a treatment however, not a vaccine.

These tests involved cell samples; no animal or human trials had yet been conducted. There is no further information available on this as of June 2005.

In literature

In his book Biohazard, former Soviet biological warfare researcher Ken Alibek claimed that the former Soviet Union experimented extensively with use of Ebola as a biological weapon, including a genetically engineered version combined with the smallpox virus to increase the degree of contagion and lethality.

The book Executive Orders by Tom Clancy describes an extensive bioterrorist attack on the United States via a newly discovered strain of Ebola (titularly the same strain that killed Mayinga) that propagates by air.

Richard Preston's book The Hot Zone contains a history of the research and discovery of the virus, as well as an account of an outbreak of a strain of the virus near Washington DC.

A modified version of the Ebola virus also appears in another Tom Clancy novel, Rainbow Six. The modified virus is slated for release at the Olympic Games, with the intent to kill every living person, except for those who are radical environmentalists.

In the Doctor Who spin off Ninth Doctor Adventures novel Only Human, a hospital is evacuated after authorities falsely claim that a patient has Ebola. The Ninth Doctor says that the cure to the disease is found in 2076.

In the DC Universe, a mutation of the virus was created by The Order Of Saint Dumas (those who created Azrael) and subsequently released by Ra's Al Ghul himself in Gotham City, causing the death of many citizens. This version is named Ebola Gulf-A and called "The Clench". Many years later, in a possible future (Elseworlds' book Brotherhood of the Bat) a new version of this virus is released by Ra's causing the death of the 99% of all humans. This new version is named Ebola Honduras.

The general concept of a highly infectious blood-borne haemorrhagic virus was used to horrifying effect in the 2002 movie 28 Days Later, directed by Danny Boyle. Although the agent in 28 Days Later was a fictional, engineered pathogen called "Rage", some parallels with Ebola are very evident.

A victim in an episode of CSI: Crime Scene Investigation is thought to be infected with Ebola, which turns out to be a false-positive.

In the 1995 movie, Outbreak, a disease that is Ebola-like, causing extreme hemorrhaging, is fought against by the protagonists. The disease is called Motaba, and is based in Zaire. During the movie, the death rate of the virus is pronounced to be near 100%, killing almost all that contract it, like Ebola. Also, in a scene they show a picture of the Motaba virus, which actually is a picture of the Ebola virus.

The 1996 Hong Kong exploitation film Ebola Syndrome revolves around an outbreak of the virus following the main character's visit to an infected South African tribe. The film uses creative license with the virus; Victims die within 72 hours and 1 in 10 million people is a "carrier" of the virus (that is to say, they can spread the virus but do not suffer themselves).

On the television show, 7 Days, a government lab in Gettysburg, Pennsylvania had created a mutated, highly contagious, one hundred percent fatal form of the ebola virus for medical and vaccine research. A religious zealot steals a sample of the virus and releases it in the flight crew lounge in the Gettysburg International Airport, believing it to be the will of God to purge the world of the wicked. In less than a week, the virus infects over ninety eight percent of the world. Only through the actions of chrononaut Frank Parker and the Back Step crew is the event undone by traveling back in time seven days. This episode was called "The Gettysburg Virus".

In the bestselling video game series Resident Evil, the T-Virus, which kills its carriers and brings them back to life as flesh-eating zombies, is created from two separate viruses. The Ebola virus is one of them, which causes the extreme hemorraging.

In season 3 of the hit show "24", a virus is threatened to be released in the United States. The symptoms of the virus relates to Ebola Hemorragic Fever. One of the characters who believed was infected with the virus said, "It's like that Ebola thing, right? It's gonna eat me alive..."

Myths

Much representation of the Ebola virus in fiction and the media is considered exaggerated.

Myth: The virus kills so fast that it has little time to spread. Victims die very soon after contact with the virus.

Reality: The incubation time is actually 2-21 days25, but usually 5-8 days with a mean of 6.2. The average time from onset of early symptoms to death varies in the range 3-21 days, with a mean of 10.127

Myth: The virus symptoms are horrifying beyond belief. Victims of Ebola suffer from squirting blood, liquifying flesh, zombie-like faces and dramatic projectile bloody vomiting.

Reality: Only a tiny fraction of Ebola victims have severe bleeding that would be even somewhat dramatic to witness. Approximately 10% of patients suffer some bleeding, but this is often internal, or subtle (e.g. bleeding from the gums). Ebola symptoms are usually limited to extreme exhaustion, digestive complaints (vomiting and diarrhea) a high fever, headaches and body pains.

The following is an excerpt from Ed Regis's interview21 with Philippe Calain, M.D. Chief Epidemiologist, CDC Special Pathogens Branch, Kikwit 1995:

At the end of the disease the patient does not look, from the outside, as horrible as you can read in some books. They are not melting. They are not full of blood. They're in shock, muscular shock. They are not unconscious, but you would say 'obtunded', dull, quiet, very tired. Very few were hemorrhaging. Hemorrhage is not the main symptom. Less than half of the patients had some kind of hemorrhage. But the ones that bled, died.

Many of the exaggerated stories about Ebola virus in Preston's book The Hot Zone are refuted in the book "Level 4: Virus Hunters of the CDC" by Joe McCormick (an employee of the CDC at the time of the early outbreaks).

See also

References

  1. "Fruit bats may carry Ebola virus". BBC News. December 1, 2005.
  2. "Vaccines protect monkeys from Ebola, Marburg". CBC News. June 5, 2005.
  3. "Breakthrough in Ebola Vaccine". BBC News. August 6, 2003.
  4. Busharizi, Paul. Ebola Hits Uganda’s Tourism Revival Effort. Planet Ark. 27 December 2000. 3 September 2003.
  5. Centers for Disease Control and Prevention and World Health Organization. Infection for Health Control of Viral Hemorrhagic Fevers in the African Health Care Setting. Atlanta, Center for Disease Control and Prevention, 1998. 3 September 2003.
  6. Draper, Allison Stark. Ebola. New York: The Rosen Publishing Group, Inc., 2002.
  7. Ebola Hemorrhagic Fever. Centers for Disease Control Special Pathogens Branch. 8 September 2003.
  8. Ebola Hemorrhagic Fever Table Showing Known Cases and Outbreaks, in Chronological Order. Centers for Disease Control and Prevention. 18 October 2002. 3 September 2003.
  9. Fact Sheet Number 103 Ebola Hemorrhagic Fever. World Health Organization. December 2000. 3 September 2003.
  10. Filoviruses. Centers for Disease Control Special Pathogens Branch. 3 September 2003.
  11. Horowitz, Leonard G. Emerging Viruses: AIDS & Ebola — Nature, Accident, or Intentional?. Rockport, MA: Tetrahedron, Inc., 1996.
  12. Preston, Richard. The Hot Zone. New York: Anchor Books Doubleday, 1994.
  13. Preston, Richard. The Demon in the Freezer.Ballantine Book by Random House, 2002.
  14. Russell, Brett. What are the Chances? ­Ebola FAQ. 3 September 2003.
  15. TED Case Study: Ebola and Trade. Trade and Environment Databases. May 1997. 7 November 2003.
  16. Oplinger, Anne A. NIAID Ebola Vaccine Enters Human Trial. NIAID: The National Institute of Allergy and Infectious Diseases. November 2003. 3 May 2005.
  17. Live attenuated recombinant vaccine protects nonhuman primates against Ebola and Marburg viruses PubMed 5 June 2005
  18. Lethal experimental infection of rhesus monkeys with Ebola-Zaire (Mayinga) virus by the oral and conjunctival route of exposure PubMed February 1996 Jaax/Davis/Geisbert/Jahrling
  19. Transmission of Ebola virus (Zaire strain) to uninfected control monkeys in a biocontainment laboratory PubMed December 1995
  20. Lethal experimental infections of rhesus monkeys by aerosolized Ebola virus PubMed August 1995
  21. Marburg and Ebola viruses as aerosol threats PubMed 2004 USAMRIID
  22. Other viral bioweapons: Ebola and Marburg hemorrhagic fever PubMed 2004
  23. Regis, Ed. Virus Ground Zero; Simon & Schuster: New York, 1996; p104
  24. Ebola Control (DRAFT) --Toolkit for Volunteers* Red Cross Red Crescent
  25. Questions and Answers about Ebola Hemorrhagic Fever, Center for Disease Control (CDC)
  26. Information on genus Ebolavirus
  27. J. Infect. Dis. 1999 179 S1-S7
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