Ebola virus disease

Health specialists prepare for work in an isolation ward for patients at the Medecins Sans Frontieres facility in southern Guinea

A Liberian nurse is being sprayed with disinfectant after preparing several bodies of victims of Ebola for burial on August 1, 2014. 

People read the comments on current events on a blackboard in Monrovia, Liberia, Saturday Aug. 2, 2014, as the deadly Ebola virus claims hundreds of lives in the West Africa region.

A Liberian street vendor wears protective gloves as a precaution to prevent infection with the deadly Ebola virus while transacting business with customers in downtown Monrovia, Liberia

A nurse from Liberia sprays preventives to disinfect the waiting area for visitors at the ELWA Hospital where a US doctor Kent Bradley is being quarantined in the hospitals isolation unit having contracted the Ebola virus, Monrovia, Liberia

Staff of the Christian charity Samaritan's Purse put on protective gear in the ELWA hospital in the Liberian capital Monrovia

Body of evidence: health workers transport a casket of a nun whose death resulted from an Ebola infection in Zaire in 1995

Peter Piot in Yambuku, northern Congo (then Zaire), in 1976, where he was part of the original team to discover the Ebola virus

A member of Doctors Without Borders helps to unload protection and healthcare materials in Guinea

Doctors in protective gear work inside the Medecins Sans Frontieres isolation ward as Guinea faced the worst ever outbreak of the Ebola virus

The Liberian daughter of a woman that died of Ebola is in tears as her mother is taken for burial from the isolation unit in Foya, Lofa County, Liberia July 2, 2014. 

Protective gear including boots, gloves, masks and suits, drying after being used in a treatment room in the ELWA hospital in the Liberian capital Monrovia on July 24. 

A nurse from Liberia disinfects the waiting area for visitors at the ELWA Hospital in Monrovia, Liberia, July 28, 2014, where US doctor Kent Bradley was quarantined after contracting the Ebola virus.

A boy walks through an empty class room on July 31, 2014 in Monrovia. Liberia announced on July 30 it was shutting all schools and placing "non-essential" government workers on 30 days' leave in a bid to halt the spread of the deadly Ebola epidemic raging in West Africa.

Liberian Deputy Health Minister Tolbert Nyensuah talks with protesters on the importance of burying Ebola victims in Johnsonville outside Monrovia, Liberia August 2, 2014. The military police were called in to control youths from the Johnsonville community who staged a protest against the government's decision to bury Ebola victims in Johnsonville.

Liberian children wash hands before entering a church service to pray for the end of Ebola at the Providence Baptist Church in Monrovia, Liberia, August 3, 2014

Liberian Christians hold holy communion in gloves to avoid contact with the deadly Ebola virus during a service at the Providence Baptist Church in Monrovia, Liberia August 3, 2014. 

Nigeria health officials wait to screen passengers at the arrival hall of Murtala Muhammed International Airport in Lagos, Nigeria, Monday, Aug. 4, 2014. Nigerian authorities on Monday confirmed a second case of Ebola in Africa's most populous country, an alarming setback as officials across the region battle to stop the spread of a disease.

People queue outside a bank as fear spreads that some buildings dealing with the public might be closed due to the spread of the deadly Ebola virus, in the city of Monrovia, Liberia, Monday, Aug. 4, 2014.

Liberian members of the Women of Peace Building Network in Monrovia, Liberia, August 4, 2014 as they observe two weeks of fasting and praying for God's intervention in eradicating the deadly Ebola virus. According to statistics from the United Nations, 887 people have died from the Ebola outbreak, making it the worst ever in history. The Liberian government has ordered that the bodies of people killed by the Ebola virus must be cremated following strong reactions from communities objecting against the burial of Ebola victims in their areas.

A view of gloves and boots used by medical staff, drying in the sun, at a center for victims of the Ebola virus in Guekedou, on April 1, 2014. The viral haemorrhagic fever epidemic raging in Guinea is caused by several viruses which have similar symptoms -- the deadliest and most feared of which is Ebola.

Members of Doctors Without Borders (MSF) wearing protective gear walk outside the isolation ward of the Donka Hospital, on July 23, 2014 in Conakry. Ebola first emerged in 1976 in what is now the Democratic Republic of Congo, and is named after a river in that country

Members of Doctors Without Borders (MSF) put on protective gear at the isolation ward of the Donka Hospital, on July 23, 2014 in Conakry.

In this 2014 photo provided by the Samaritan's Purse aid organization, Dr. Kent Brantly, left, treats an Ebola patient at the Samaritan's Purse Ebola Case Management Center in Monrovia, Liberia. On Saturday, July 26, 2014, the North Carolina-based aid organization said Brantly tested positive for the disease and was being treated at a hospital in Monrovia.

Members of Doctors Without Borders (MSF) wear protective gear at the isolation ward of the Donka Hospital in Conakry on July 23, 2014.

In Monday, July 15, 2014 photo, a woman, center, walks near the Arwa clinic, center rear, that was closed after the clinic doctor got infected by the Ebola virus in the capital city of Freetown, Sierra Leone.

A 10-year-old boy is given a medical blouse after being taken out of quarantine following his mother's death caused by the ebola virus, in the Christian charity Samaritan's Purse Ebola treatment center, at the ELWA hospital in the Liberian capital Monrovia, on July 24, 2014.

In this photo taken on Monday, July 28, 2014, people hang out in a street under a banner which warns people to be cautious about Ebola, in Monrovia, Liberia.

A picture taken on July 24, 2014 shows a staff member of the Christian charity Samaritan's Purse wearing protective whilst entering a room where patients are kept in the ELWA hospital in the Liberian capital Monrovia.

A pharmacist searches for drugs in a pharmacy in Lagos on July 26, 2014. Nigeria was on alert against the possible spread of Ebola on July 26, a day after the first confirmed death from the virus in Lagos, Africa's biggest city and the country's financial capital.

Members of the Guinean Red Cross stick information concerning the Ebola virus during an awareness campaign on April 11, 2014 in Conakry. Guinea has been hit by the most severe strain of the virus, known as Zaire Ebola, which has had a fatality rate of up to 90 percent in past outbreaks, and for which there is no vaccine, cure or even specific treatment. The World Health Organization (WHO) has described west Africa's first outbreak among humans as one of the most challenging since the virus emerged in 1976 in what is now the Democratic Republic of Congo.

Health workers wearing protective suits walk in an isolation center for people infected with Ebola at Donka Hospital in Conakry on April 14, 2014.

A picture taken on June 28, 2014 shows members of Doctors Without Borders (MSF) putting on protective gear at the isolation ward of the Donka Hospital in Conakry, where people infected with the Ebola virus are being treated.

In this March 28, 2014 photo provided by Medecins Sans Frontieres (Doctors Without Borders), healthcare workers from the organization prepare isolation and treatment areas for their Ebola virus operations in Gueckedou, Guinea. One preacher advocated fasting and prayer to spare people from a virus that usually leads to a horrible death. Some people pray that the Ebola virus stays confined to a rural district. Others are unruffled and say the outbreak will blow over.

Doctors Without Borders staff members carry the body of a person killed by viral haemorrhagic fever at a center for victims of the Ebola virus in Gueckedou, on April 1, 2014.

Volunteers lower a corpse, which is prepared with safe burial practices to ensure it does not pose a health risk to others and stop the chain of person-to-person transmission of Ebola, into a grave in Kailahun August 2, 2014. 

A volunteer walks at a cemetery near the Mediciens Sans Frontieres treatment centre in Kailahun August 2, 2014. 

Volunteers prepare to remove the bodies of people who were suspected of contracting Ebola and died in the community in the village of Pendebu, north of Kenema August 2 , 2014. 

Health workers, wearing head-to-toe protective gear, prepare for work outside an isolation unit in Foya District, Lofa County, Liberia in this July 2014 UNICEF handout photo. 

Girls look at a poster, distributed by UNICEF, bearing information on and illustrations of best practices that help prevent the spread of Ebola in Voinjama, Lofa County, Liberia in this April 2014 UNICEF handout photo. 

A UNICEF worker speaks with drivers of motorcycle taxis about the symptoms of Ebola virus disease (EVD) and best practices to help prevent its spread in Voinjama, Lofa County, Liberia in this April 2014 UNICEF handout photo. 

Medical staff working with Medecins sans Frontieres (MSF) prepare to bring food to patients kept in an isolation area at the MSF Ebola treatment center in Kailahun, Sierra Leone July 20, 2014. 

Medical staff working with Medecins sans Frontieres (MSF) put on their protective gear before entering an isolation area at the MSF Ebola treatment center in Kailahun, Sierra Leone July 20, 2014. 

Health workers carry the body of an Ebola virus victim in Kenema, Sierra Leone June 25, 2014. 

Medical staff take a blood sample from a suspected Ebola patient at the government hospital in Kenema, Sierra Leone July 10, 2014. 

A health worker removes his protective suit as he emerges from an isolation area at the Medecins sans Frontieres Ebola treatment center in Kailahun, Sierra Leone July 20, 2014. 

A health worker with disinfectant spray walks down a street outside the government hospital in Kenema, Sierra Leone July 10, 2014. 

Health workers teach people about the Ebola virus and how to prevent infection, in Conakry, Guinea, on March 31, 2014.

Health workers take blood samples for Ebola virus testing at a screening tent in the local government hospital in Kenema, Sierra Leone June 30, 2014. 

Government health workers are seen during the administration of blood tests for the Ebola virus in Kenema, Sierra Leone June 25, 2014. 

A view of the isolation block of a hospital where Ebola victims are being treated in Macenta, Guinea March 27, 2014. 

Workers from Doctors Without Borders unload emergency medical supplies to deal with an Ebola outbreak in Conakry, Guinea March 23, 2014. 

Government health workers administer blood tests to check for the Ebola virus in Kenema, Sierra Leone June 25, 2014. 

Medical staff put on protective gear in Kenema government hospital before taking a sample from a suspected Ebola patient in Kenema, Sierra Leone July 10, 2014. 

A scientist separates blood cells from plasma cells to isolate any Ebola RNA in order to test for the virus at the European Mobile Laboratory in Gueckedou, Guinea April 3, 2014. 

View of an isolation center for people infected with Ebola at Donka Hospital in Conakry.

Ebola virus disease

Key facts

•Ebola virus disease (EVD), formerly known as Ebola haemorrhagic fever, is a severe, often fatal illness in humans.

•EVD outbreaks have a case fatality rate of up to 90%.

•EVD outbreaks occur primarily in remote villages in Central and West Africa, near tropical rainforests.

•The virus is transmitted to people from wild animals and spreads in the human population through human-to-human transmission.

•Fruit bats of the Pteropodidae family are considered to be the natural host of the Ebola virus.

•Severely ill patients require intensive supportive care. No licensed specific treatment or vaccine is available for use in people or animals.

Ebola first appeared in 1976 in 2 simultaneous outbreaks, in Nzara, Sudan, and in Yambuku, Democratic Republic of Congo. The latter was in a village situated near the Ebola River, from which the disease takes its name.

Genus Ebolavirus is 1 of 3 members of the Filoviridae family (filovirus), along with genus Marburgvirus and genus Cuevavirus. Genus Ebolavirus comprises 5 distinct species:

•Bundibugyo ebolavirus (BDBV)•Zaire ebolavirus (EBOV)•Reston ebolavirus (RESTV)•Sudan ebolavirus (SUDV)•Taï Forest ebolavirus (TAFV).

BDBV, EBOV, and SUDV have been associated with large EVD outbreaks in Africa, whereas RESTV and TAFV have not. The RESTV species, found in Philippines and the People’s Republic of China, can infect humans, but no illness or death in humans from this species has been reported to date.

Transmission

Ebola is introduced into the human population through close contact with the blood, secretions, organs or other bodily fluids of infected animals. In Africa, infection has been documented through the handling of infected chimpanzees, gorillas, fruit bats, monkeys, forest antelope and porcupines found ill or dead or in the rainforest.

Ebola then spreads in the community through human-to-human transmission, with infection resulting from direct contact (through broken skin or mucous membranes) with the blood, secretions, organs or other bodily fluids of infected people, and indirect contact with environments contaminated with such fluids. Burial ceremonies in which mourners have direct contact with the body of the deceased person can also play a role in the transmission of Ebola. Men who have recovered from the disease can still transmit the virus through their semen for up to 7 weeks after recovery from illness.

Health-care workers have frequently been infected while treating patients with suspected or confirmed EVD. This has occurred through close contact with patients when infection control precautions are not strictly practiced.

Signs and symptoms

EVD is a severe acute viral illness often characterized by the sudden onset of fever, intense weakness, muscle pain, headache and sore throat. This is followed by vomiting, diarrhoea, rash, impaired kidney and liver function, and in some cases, both internal and external bleeding. Laboratory findings include low white blood cell and platelet counts and elevated liver enzymes.

People are infectious as long as their blood and secretions contain the virus. Ebola virus was isolated from semen 61 days after onset of illness in a man who was infected in a laboratory.

The incubation period, that is, the time interval from infection with the virus to onset of symptoms, is 2 to 21 days.

Diagnosis

Other diseases that should be ruled out before a diagnosis of EVD can be made include: malaria, typhoid fever, shigellosis, cholera, leptospirosis, plague, rickettsiosis, relapsing fever, meningitis, hepatitis and other viral haemorrhagic fevers.

Ebola virus infections can be diagnosed definitively in a laboratory through several types of tests:

•antibody-capture enzyme-linked immunosorbent assay (ELISA)•antigen detection tests•serum neutralization test•reverse transcriptase polymerase chain reaction (RT-PCR) assay•electron microscopy•virus isolation by cell culture.•Samples from patients are an extreme biohazard risk; testing should be conducted under maximum biological containment conditions.

Vaccine and treatment

No licensed vaccine for EVD is available. Several vaccines are being tested, but none are available for clinical use.

Severely ill patients require intensive supportive care. Patients are frequently dehydrated and require oral rehydration with solutions containing electrolytes or intravenous fluids.

No specific treatment is available. New drug therapies are being evaluated.

Natural host of Ebola virus

In Africa, fruit bats, particularly species of the genera Hypsignathus monstrosus, Epomops franqueti and Myonycteris torquata, are considered possible natural hosts for Ebola virus. As a result, the geographic distribution of Ebolaviruses may overlap with the range of the fruit bats.

Ebola virus in animals

Although non-human primates have been a source of infection for humans, they are not thought to be the reservoir but rather an accidental host like human beings. Since 1994, Ebola outbreaks from the EBOV and TAFV species have been observed in chimpanzees and gorillas.

RESTV has caused severe EVD outbreaks in macaque monkeys (Macaca fascicularis) farmed in Philippines and detected in monkeys imported into the USA in 1989, 1990 and 1996, and in monkeys imported to Italy from Philippines in 1992.

Since 2008, RESTV viruses have been detected during several outbreaks of a deadly disease in pigs in People’s Republic of China and Philippines. Asymptomatic infection in pigs has been reported and experimental inoculations have shown that RESTV cannot cause disease in pigs.

Prevention and control

Controlling Reston ebolavirus in domestic animalsNo animal vaccine against RESTV is available. Routine cleaning and disinfection of pig or monkey farms (with sodium hypochlorite or other detergents) should be effective in inactivating the virus.

If an outbreak is suspected, the premises should be quarantined immediately. Culling of infected animals, with close supervision of burial or incineration of carcasses, may be necessary to reduce the risk of animal-to-human transmission. Restricting or banning the movement of animals from infected farms to other areas can reduce the spread of the disease.

As RESTV outbreaks in pigs and monkeys have preceded human infections, the establishment of an active animal health surveillance system to detect new cases is essential in providing early warning for veterinary and human public health authorities.

Reducing the risk of Ebola infection in people

In the absence of effective treatment and a human vaccine, raising awareness of the risk factors for Ebola infection and the protective measures individuals can take is the only way to reduce human infection and death.

Pig farms in Africa can play a role in the amplification of infection because of the presence of fruit bats on these farms. Appropriate biosecurity measures should be in place to limit transmission. For RESTV, educational public health messages should focus on reducing the risk of pig-to-human transmission as a result of unsafe animal husbandry and slaughtering practices, and unsafe consumption of fresh blood, raw milk or animal tissue. Gloves and other appropriate protective clothing should be worn when handling sick animals or their tissues and when slaughtering animals. In regions where RESTV has been reported in pigs, all animal products (blood, meat and milk) should be thoroughly cooked before eating.

Controlling infection in health-care settings

Human-to-human transmission of the Ebola virus is primarily associated with direct or indirect contact with blood and body fluids. Transmission to health-care workers has been reported when appropriate infection control measures have not been observed.

It is not always possible to identify patients with EBV early because initial symptoms may be non-specific. For this reason, it is important that health-care workers apply standard precautions consistently with all patients – regardless of their diagnosis – in all work practices at all times. These include basic hand hygiene, respiratory hygiene, the use of personal protective equipment (according to the risk of splashes or other contact with infected materials), safe injection practices and safe burial practices.

Health-care workers caring for patients with suspected or confirmed Ebola virus should apply, in addition to standard precautions, other infection control measures to avoid any exposure to the patient’s blood and body fluids and direct unprotected contact with the possibly contaminated environment. When in close contact (within 1 metre) of patients with EBV, health-care workers should wear face protection (a face shield or a medical mask and goggles), a clean, non-sterile long-sleeved gown, and gloves (sterile gloves for some procedures).

Laboratory workers are also at risk. Samples taken from suspected human and animal Ebola cases for diagnosis should be handled by trained staff and processed in suitably equipped laboratories.

The Ebola virus and it’s close relative the Marburg virus are members of the Filoviridae family. These viruses are the causative agents of severe hemorrhagic fever, a disease with a fatality rate of up to 90%. The Ebola virus infects mainly the capillary endothelium and several types of immune cells. The symptoms of Ebola infection include maculopapular rash, petechiae, purpura, ecchymoses, dehydration and hematomas.

Since Ebola was first described in 1976, there have been several epidemics of this disease. Hundreds of people have died because of Ebola infections, mainly in Zaire, Sudan, Congo and Uganda. In addition, several fatalities have occurred because of accidents in laboratories working with the virus. Currently, a number of scientists claim that terrorists may use Ebola as a biological weapon.

In the 3D model presented in this study, Ebola-encoded structures are shown in maroon, and structures from human cells are shown in grey. The Ebola model is based on X-ray analysis, NMR spectroscopy, and general virology data published in the last two decades.

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cast Ebola virus disease

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Music Lorena McKennitt

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