Ebola Virus Disease Medical Briefing

Ebola virus disease (EVD) transmission bat

Written by Dr Adrian Hyzler, Chief Medical Officer and Head of Medical Communications

Updated: July 2019

Ebola virus disease (EVD) used to be known as Ebola Haemorrhagic Fever because of the association with bleeding. It is a rare but often fatal disease in humans that is found principally in sub-Saharan Africa. It is transmitted to people from wild animals but can also spread from human-to-human.

Ebola virus first came to light in 1976 in two simultaneous outbreaks, one in what is now known as South Sudan and the other in the Democratic Republic of Congo. The name is taken from the proximity of the outbreak to the Ebola River, in DR Congo. Since then there have been a number of isolated small outbreaks dotted around sub-Saharan Africa.

The largest outbreak to date took place in West Africa between 2013 and 2016 and claimed over 11,000 lives from 28,600 confirmed cases spread across Guinea, Sierra Leone and Liberia. It was later reported that 10% of the dead were healthcare workers. The current outbreak in DR Congo (the 10th in this country) is the second largest in history and has been fuelled by security concerns that have hampered the public health response. Despite this, as of July 2019, authorities had restricted cross-border spread to just two victims who died in Uganda in June 2019, after they attended the funeral of a relative who succumbed to EVD in DR Congo.

Case fatality rates reached levels as high as 75% mortality in the West Africa outbreak but a greater understanding of the disease and use of experimental vaccines have reduced this to between 50-60% in the current outbreak in DR Congo. Public Health authorities understand that the key to controlling outbreaks is with strong community engagement.


  • Ebola virus disease (EVD) is a rare but severe, often fatal illness in humans – the fatality rate is over 50%.
  • The virus is transmitted to people from wild animals and spreads in the human population through human-to-human transmission through contact with body fluids and sexual transmission.
  • Community engagement is key to successfully controlling outbreaks.
  • Personal prevention relies on avoiding contact with all bodily fluids of victims, both alive and dead, and avoiding the consumption of raw or undercooked ‘bush-meat’
  • Good outbreak control relies on applying a package of interventions: case management, infection prevention and control practices, surveillance and contact tracing, a good laboratory service, safe and dignified burials and social mobilisation.
  • Vaccines to protect against Ebola are under development and have been used to help control the spread of Ebola outbreaks in Guinea and in DR Congo with highly effective results.
  • Early supportive care with rehydration improves survival. There is no licensed treatment proven to treat the virus but a range of blood, immunological and drug therapies are under development.

TRANSMISSION | How do you get Ebola Virus?

It is believed that the virus is animal-borne with the most likely ‘reservoir’ for the virus being the Angolan free-tailed bat. The bats can transmit the virus to other animals such as primates, many varieties of fruit bats, wild pigs, porcupines and antelopes. The virus can spread through direct contact with the blood, tissues or bodily fluids of infected animals or through the consumption of raw or undercooked, infected “bush-meat”.

It is spread within the community through direct contact with bodily fluids of someone who has EVD or has recently died from it. The virus gets in through broken skin or mucous membranes in the eyes, nose or mouth. The virus can also be spread from human-to-human through sexual contact.

The Ebola virus CANNOT spread to others until a person develops signs or symptoms of EVD.

SYMPTOMS | What are the symptoms of Ebola Virus Disease?

Symptoms appear from two days to three weeks after coming into contact with the virus – it usually takes about 10 days. The initial symptoms are very similar to many viral illnesses, typhoid, dengue or malaria. The most common presenting symptom is fever.

It is vital that the greatest care is taken in the healthcare setting to prevent spread via medical equipment. Proper disinfecting and disposal of instruments such as needles and syringes are very important. The virus can survive for several hours on surfaces, but for several days in body fluids, like blood.

There is no evidence that mosquitoes or ticks can transmit EVD.

Common symptoms are…

  • Fever
  • Severe headache
  • Muscle aches
  • Weakness and fatigue
  • Watery diarrhoea
  • Vomiting
  • Abdominal pain
  • Rash in about half of all cases, about a week after symptoms begin
  • Unexplained bruising or bleeding – coughing up blood, vomiting blood or blood in the stool. Also bleeding in the eyes and skin may occur

DIAGNOSIS | How is Ebola Virus Disease diagnosed?

A person with vague symptoms of fever, headache and weakness and potential exposure to Ebola Virus, should be assumed to be EVD positive, unless proven otherwise.

It is not possible to diagnose EVD immediately after infection.

They should be immediately isolated and moved to an Ebola Treatment Centre where they can be ‘barrier nursed’, with full protective measures, until blood samples can be analysed to confirm or exclude EVD. It may take up to three days after symptoms start for the virus to reach detectable levels.

Oral fluid specimens can be taken from deceased patients or when blood collection is not possible and sent to the lab for analysis. All samples collected are an extreme biohazard and should be triple packaged for transportation.

TREATMENT | How is Ebola Virus Disease treated?

There is no specific treatment or drug that is available to treat EVD. The goal of treatment is to treat the symptoms and provide supportive care within a hospital setting in order to improve the chances of survival.

The mainstay of treatment is the provision of intravenous fluids and electrolytes to maintain hydration – the main cause of death is by dehydration from fluid loss, usually within the first two weeks of infection. Patients may also be given oxygen to help with breathing and drugs to control symptoms of vomiting and diarrhoea. Pain medication and antibiotics may also be necessary.

There is no specific treatment or drug that is available to treat EVD.

Over half of all EVD patients will die from the disease between one and two weeks of becoming infected. Recovery is dependent on good supportive care and the patient’s own immune response to the virus. Recovery, if it is to occur, usually begins between seven to 14 days after first symptoms appear. Once a person has recovered they develop antibodies that can prevent further infection for up to 10 years, possibly longer.

Ebola survivors may experience difficult side effects after their recovery, such as tiredness, muscle aches, eye and vision problems and stomach pain. Mental health issues are very common in survivors. Survivors may also experience stigma as they re-enter their communities.

In women who have been infected while pregnant, the virus persists in the placenta, amniotic fluid and foetus. In women who have been infected while breastfeeding, the virus may persist in breast milk.

The first ever multi-drug randomised controlled trial is currently being conducted in DR Congo to evaluate the effectiveness and safety of potential life-saving drugs for EVD.

PREVENTION | What precautions should I take to prevent getting Ebola?

When travelling to a region where Ebola virus is present, it is important to take the following precautions:

  • Wash and peel fruit and vegetables before consumption
  • Wash hands regularly and carefully using soap and water (or alcohol gel when soap is unavailable)
  • Avoid contact with all blood and bodily fluids
  • Avoid contact with items of clothing, bedding, medical equipment etc. that may have come into contact with an infected person
  • Avoid funeral or burial rituals that require handling the body of an EVD victim
  • Avoid contact with bats and any wild animals, their blood or bodily fluids or raw meat of such animals (“bush-meat”)
  • Avoid sexual contact with anyone who has or has had EVD – use barrier contraception.

After returning to your home country from an area affected by Ebola, monitor your health for 21 days and seek immediate medical care if you develop any of the above symptoms of EVD. Exit screening is in operation when leaving EVD affected areas.

VACCINATION | Is there a vaccine available for Ebola Virus Disease?

There is no vaccine licensed for use by travellers to Ebola affected regions.

However, there are experimental and unlicensed vaccines, developed during the West Africa outbreak, that are available to the public health authorities of the affected countries. These are controlled by the World Health Organisation and are being used in controlled “ring vaccination” protocols. It has been found that the most effective way of controlling the spread of the virus is by vaccinating ever increasing circles of contacts and potential contacts, radiating outwards from the EVD affected person. They are also given to front line workers in advance of potential contact.

More than 100,000 people have to date been vaccinated and initial data on the efficacy of these vaccines indicate that they are highly effective.

OUTBREAK CONTROL | How can the disease be managed?

Good outbreak control relies on a number of interventions and, crucially, strong community engagement. It is essential that a reliable network is put in place to:

  • Manage cases
  • Trace contacts
  • Establish a reliable and efficient laboratory network
  • Administer vaccination programmes
  • Promote safe burial practises
  • Administer community education programmes
  • Provide accurate surveillance of case incidence.

In the current outbreak in Democratic Republic of Congo the most important factor in preventing the control and elimination of the disease is the presence of armed insurgents who have destroyed treatment centres, disrupted vaccination programmes and caused mass people movements, thus causing the spread of the disease. Securing the region is the most important consideration to permit outbreak control.

Raising awareness of risk factors for Ebola infection and protective measures (including vaccination) that individuals can take is an effective way to reduce human transmission.

Risk reduction messaging should focus on several factors:
  • Reducing the risk of wildlife-to-human transmission from contact with infected fruit bats, monkeys, apes, forest antelope or porcupines and the consumption of their raw meat. Animals should be handled with gloves and other appropriate protective clothing. Animal products (blood and meat) should be thoroughly cooked before consumption.
  • Reducing the risk of human-to-human transmission from direct or close contact with people with Ebola symptoms, particularly with their bodily fluids. Gloves and appropriate personal protective equipment should be worn when taking care of ill patients. Regular hand washing is required after visiting patients in hospital, as well as after taking care of patients at home.
  • Outbreak containment measures, including safe and dignified burial of the dead, identifying people who may have been in contact with someone infected with Ebola and monitoring their health for 21 days, the importance of separating the healthy from the sick to prevent further spread, and the importance of good hygiene and maintaining a clean environment.
  • Reducing the risk of possible sexual transmission. WHO recommends that male survivors of EVD practice safer sex and hygiene for 12 months from onset of symptoms or until their semen tests negative twice for Ebola virus. Contact with body fluids should be avoided and washing with soap and water is recommended.