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EBOLA: The Basic facts

Q: What is Ebola?

A: Ebola is a filovirus.

Ebola is also the short name for the disease Ebola viruses cause. You will see the disease called Ebola virus disease, EVD or just Ebola.

Ebola (the disease) used to be called a viral hemorrhagic fever or VHF. But the World Health Organization and other expert groups are moving away from the use of that term to describe Ebola disease because not everyone who contracts Ebola experiences the visible hemorrhaging – profuse bleeding – that led to that term.

Q: Who discovered Ebola?

A: There were a number of people involved in discovering Ebola. To call one person “the discoverer” of Ebola misrepresents the history of the disease.

Three scientific teams are credited with the discovery: the Institut de Médecine Tropicale Prince Leopold and the University of Antwerp, Belgium; the Microbiological Research Establishment in Porton Down, Salisbury, England and the U.S. Center for Disease Control – now the Centers for Disease Control and Prevention — in Atlanta, Georgia, USA.

The teams at Antwerp and Porton Down identified that blood from an early victim in Zaire (now the Democratic Republic of the Congo) contained filoviruses; the CDC team did the work to confirm that this was not Marburg (a filovirus discovered in 1967) but a brand new virus.  You can see the announcement of the first 2 Ebola outbreaks (which occurred almost simultaneously) on page 327 of the World Health Organization’s Weekly Epidemiological Record for Oct. 15, 1976.

The three groups each published a report of their findings in the March 12, 1977 issue of The Lancet. There were 15 authors on the three papers. A number of those scientists and others from the United States, Belgium, Zaire, France and South Africa were involved in the investigation into the first known Ebola outbreak. This larger group became known as the International Commission for the Investigation and Control of Ebola Hemorrhagic Fever in Zaire.

Q: How did Ebola get its name?

A: Karl Johnson, who was the head of the CDC’s special pathogens team in 1976, was named scientific director of the International Commission. Johnson had discovered several other viruses and was sensitive to the fact that naming a pathogen after the place where it was discovered was stigmatizing — it would forever link a place with a disease, in this case a deadly one. He proposed naming it after a local river, Ebola. The proposal was agreed to by the other scientists involved.

The CDC team explained the choice of the name of the new virus in their March 1977 Lancet article:   “In deference to the countries involved and to the lack of specific knowledge of the original natural source of the virus, it is also suggested that no names of countries or specific towns be used.”

Q: What is a filovirus?

A: It is a family of viruses containing two known members – Ebola viruses and Marburg virus.  Ebola and Marburg are like cousin viruses. The diseases they cause in people are very similar and so is the rate of death among known cases.The virus family got its name from the way the viruses look under a microscope. They resemble long filaments.

CDC Ebola virus

Q: Is there one type of Ebola, or many?

A: There are five known types or “species” of Ebola viruses. They are Ebola Zaire, Ebola Sudan, Ebola Reston, Ebola Tai Forest (which is sometimes called Ivory Coast or Cote d’Ivoire) and Ebola Bundibugyo.

The different types of virus have different characteristics. For example, while it is known that a few people have been infected with the Reston virus, it does not appear to make humans sick. It does infect and kill primates, however.

The other four known strains do infect humans. However, the Tai Forest strain has only been seen once, in 1994. A scientist who as doing and autopsy of a dead chimpanzee in Cote d’Ivoire’s Tai Forest became infected. He was very sick, but he survived.

Ebola Zaire is the deadliest of the viruses, sometimes killing as many as 90 per cent of people it infects. It is the virus responsible for the massive West African outbreak that began in late 2013.

The strains that have caused the most outbreaks are Ebola Zaire and Ebola Sudan.

The remaining type is called Bundibugyo, because it was first seen in the Bundibugyo District of western Uganda.

Q: What is the natural habitat or reservoir of these viruses?

A: That is not currently known.  It is believed these viruses normally live in some types of bats and occasionally make their way into humans. Again, how that occurs isn’t fully known.

It could be that outbreaks begin when a person comes in contact with an infected bat. Some outbreaks have occurred among workers who mine in caves infested with bats. And two tourists – an American woman and a woman from the Netherlands – became infected with the Marburg virus while visiting a cave in Uganda where bat colonies live.

Scientists think that sometimes bats infect monkeys or other primates and then people who butcher those monkeys to prepare them to be eaten become infected.  The Ebola Zaire outbreak in the Democratic Republic of the Congo in the summer of 2014 is believed to have started when a woman butchered some bush meat her husband had found in the forest.

Once the virus has crossed from an animal to a human, there is a risk that that person will spread the virus to other people, causing a human outbreak. But that doesn’t always happen.

WFSJ_Infographique Ebola transmission_EN[8]

Q: The West African epidemic is described as the largest in history, far larger than earlier outbreaks. What was a typical size of Ebola outbreak before 2014?

A: There is a wide range in size of earlier outbreaks. Some involved fewer than 10 people but many ranged between 20 to 150 cases. The largest previous outbreak was in Uganda in 2000, with 425 cases. This outbreak chart and map on the site of the U.S. Centers for Disease Control and Prevention provide an overview of all known outbreaks.

Q: Which countries have had outbreaks?

A: Until 2014 it was thought that the Ebola viruses that make people sick were only found in central and equatorial Africa. Outbreaks have occurred in what is now the Democratic Republic of the Congo (DRC), the Republic of Congo, Gabon, Sudan (South Sudan) and Uganda. The countries that have had the most outbreaks are the DRC (6) and Uganda (5).

Other than the single case in the Tai forest in Ivory Coast, Ebola had not been seen in West Africa before 2014.

Several other countries have had “imported” cases, which means that a patient from a country with an outbreak traveled elsewhere. For instance, South Africa had an imported case in an infected traveller from Gabon in 1996; he infected a nurse who cared for him. There were also a few Ebola cases stemming from lab accidents; these happened in Britain in 1976 and in Russia in 1996 and 2004.

The 2014 outbreak actually started in December of 2013, but it was not recognized until March 2014. It began in Guinea and spread to Sierra Leone and Liberia. This was the first time Ebola has triggered a major human outbreak outside of its previous known territory.

The West African epidemic has brought Ebola to many more countries. From the three outbreak countries, patients traveled or were evacuated to Nigeria, Senegal, Mali, the United States, Spain, Germany, the Netherlands, the United Kingdom and other places. In some cases, they triggered new, local outbreaks that were eventually contained. Twenty people were infected in Nigeria, for instance, and eight in Mali. A nurse in Madrid who cared for a Spanish missionary who was infected in Sierra Leone also contracted the disease, as did two nurses in Dallas, Texas, who came into contact with a patient who traveled to the U.S. from Liberia.

Q: Ebola Reston is different. Where does it come from?

A: Ebola Reston is the only one of the viruses to come from Asia — the Philippines. It has been found primarily in primates, but in 2008 it was also found to infect pigs in that country. Ebola Reston is named after the American community of Reston, Virginia, where an outbreak of fatal disease among primates imported to the United States for laboratory research occurred in 1990. The cause was discovered to be a new Ebola virus. Reston virus outbreaks in primates have occurred in the Philippines, the United States and Italy.

Q: How does Ebola spread from person to person?

A: The virus is spread through the bodily fluids of people who are infected. Ebola viruses have been found in a number of body fluids, such a blood, vomit, semen and even breast milk.  But it is believed that contact with the blood, vomit and diarrhea of infected people is the primary way the disease spreads.

Burial practices that involve cleaning and kissing the corpses of the deceased are known to permit spread of the virus; they often play a significant role in the spread of the virus.

Q: How are Ebola outbreaks contained?

A: The classic containment approach is three pronged.

1) Identify and isolate people who are infected.
2) Identify and monitor the contacts of Ebola patients, so that you can isolate them if they develop the disease.
3) Bury bodies safely. Close contact with the bodies of people who have died of Ebola can spread the disease.

Q: What are Ebola’s symptoms?

A: Early symptoms of the disease are vague and resemble those of influenza, malaria and other diseases. As infection progresses people complain about severe headaches, fever, muscle pain, and fatigue. Profuse diarrhea and vomiting is common. Some patients suffer bleeding – nose bleeds or bleeding from their gums.

Q: How long does it take for people to develop symptoms once they contract the virus?

A: The time from infection to the appearance of symptoms is called the incubation period. For Ebola this can be as short as two days and as long as 21, but the average is between eight and 10 days, according to the U.S. CDC.

Q: In the 2014 outbreak it took three months before authorities in Guinea realized they had an Ebola outbreak on their hands. And it is said Ebola can be difficult to diagnose. Why?

A: Ebola is difficult to diagnose. Ebola can look like a number of other illnesses that are seen in countries where Ebola outbreaks occur, including malaria and Lassa Fever. If doctors don’t think to test for Ebola, early cases in an outbreak can be missed. Some locales do not have Ebola tests available, and must ship blood samples to labs that can be distant from the patient.

Q: How do labs test for Ebola?

A: A blood sample is drawn when a person is suspected of having contracted Ebola. A laboratory will test the blood looking for evidence of the virus.

The timing of a test is important. In the early stage of infection a blood test can actually come back negative. Retesting is recommended in patients who are strongly suspected of having Ebola but whose first test is negative.

Sometimes scientists test people to see if they have been infected in the past. Again, they test blood samples to look for antibodies to the virus.

A team of psycho social workers from Action Contre la Faim (ACF)

Q: What treatments are available for Ebola? Do drugs or vaccines exist?

A: There are no specific drugs on the market to combat Ebola disease. Some research suggests several drugs that were developed to fight other viruses might work against Ebola.

There are a number of experimental vaccines that are being developed and tested. Tests in primates show these vaccines can prevent infection; the human studies needed to prove this are now taking place in West Africa. The epidemic in West Africa has led to a huge acceleration of drug and vaccine development.

For more on this topic, see the chapter entitled Drugs, Vaccines & Diagnostics.

Q: If there are no drugs or vaccines, how are people with EVD treated?

A: They receive what is called “supportive care.” That includes things like food, if they can eat, and fluids. People who have EVD lose a lot of fluids through diarrhea and vomiting, sometimes litres a day.

When patients become too sick, however, they may not be able to drink the volume of fluids they need. Ebola patients treated in Europe and the United States have also received intravenous (IV) fluids – fluids dripped into their veins as a standard part of their care. Some experts – including Dr. Paul Farmer of the U.S. aid group Partners in Health – have been critical of the fact that IV fluids haven’t  been available to all patients in Africa.

But others say that during the height of the outbreak, when treatment centers were turning away patients because they were full, there were not enough medical staff to give patients IV fluids. Also, delirious patients sometimes rip the IV needles out of their arms and bleed from the entry point.

Q: Why does Ebola frighten people so much?

A: The virus is not the deadliest that infects humans. Rabies is the more lethal: It kills virtually everyone it infects. But rabies does not transmit from person to person. Of the viruses that people can transmit to other people, Ebola and Marburg viruses are the most deadly.

As well, the illness can cause great suffering, with lots of vomiting, diarrhea and sometimes bringing up blood or profuse nose bleeds.  That puts people caring for Ebola patients at high risk of becoming infected. Health-care workers often make up a significant percentage of the Ebola cases in outbreaks.

The bestseller The Hot Zone: A Terrifying True Story may also have contributed to the fear surrounding Ebola. The book, which described patients’ symptoms in grisly detail–including the “liquefying” of organs–has been criticized as sensationalist; its author, Richard Preston, has said he wants to paint a more accurate picture of the disease in an updated version of the book.

The Hot Zone cover


 

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