Ebola virus disease (EVD)

Ebola virus disease (EVD) was first recognized by the scientific community in 1976, in two simultaneous outbreaks in what are now South Sudan and the Democratic Republic of Congo. The latter occurred in a village near the Ebola River, from which the disease takes its name. The 2014–2016 outbreak in West Africa spread between countries, starting in Guinea then moving across land borders to Sierra Leone and Liberia. Sporadic cases have been exported to Mali, Nigeria, United States and Spain.

The average case fatality rate for EVD depends both on the strain of virus causing the infection, and the patient’s access to early supportive care and specific treatment. It has varied from 25 per cent to 90 per cent in past outbreaks. People can get EVD through direct contact with an infected animal (zoonotic disease) or a sick or dead person infected by Ebola virus.

The following are standard case definitions to allow national health authorities to interpret data in an international context. However, during an outbreak case definitions may be adapted to the local context and the Red Cross Red Crescent should use those agreed/established by national health authorities. NB: Consider that during community-based surveillance, volunteers should use broad (simplified) case definitions (referred to as community case definitions) to recognize most or all possible cases, provide relevant risk communication and appropriate actions and encourage them to seek care. Other actors such as healthcare workers or investigators studying the cause of a disease, on the other hand, can use more specific case definitions that may require laboratory confirmation.

Routine surveillance

Suspected case: Illness with onset of fever and no response to treatment for usual causes of fever in the area, and at least one of the following signs: bloody diarrhoea, bleeding from gums, bleeding into skin (purpura), bleeding into eyes and urine. During an outbreak, the case definitions are likely to be modified to be adapted to new clinical presentation(s) or different modes of transmission related to the local event.

Probable case: Any deceased suspected case (where it has not been possible to collect specimens for laboratory confirmation) having an epidemiological link with a confirmed case.

Confirmed case: A suspected case with laboratory confirmation (positive IgM antibody, positive Polymerase chain reaction (PCR) or viral isolation).

Community-based surveillance

Alert case: Illness with onset of fever and no response to treatment of usual causes of fever in the area OR at least one of the following signs: bleeding, bloody diarrhoea, bleeding into urine OR any sudden death. If the National Society is doing community-based surveillance, a community case definition should be agreed upon with the relevant health authority.

WHO case definition source of information: https://www.who.int/csr/resources/publications/ebola/ebola-case-definition-contact-en.pdf

Single case.

• Infection when caring for those suffering from the disease may occur through contact with the body fluids of patients, or contact with fomites (e.g. clothes, bedding, needles, medical equipment contaminated with body fluids from a person who has EVD) when infection prevention precautions are not strictly practised.
• Burial ceremonies that involve direct contact with the body of the deceased are a significant driver of transmission. Mourners are at increased risk.
• People in contact with wild animals like fruit bats, apes, antelopes and monkeys, in areas where Ebola virus (EBOV) may be present.
• Health workers who do not have access to/do not use proper IPC measures while caring for Ebola patients (detected or undetected) are at highest risk of getting sick. Other patients who share a bed, room or medical equipment with Ebola patients are at very high risk.

Attack rates will vary from one outbreak to another. In case of an outbreak, consult the latest information provided by health authorities.

 Household attack rates are between 12 and 48 per cent.

• People with chronic diseases such as renal disease, cancer, chronic liver and lung disease and diabetes.
• Older people with weakened immune systems.
• Infants, young children.
• Immunosuppressed persons such as those receiving chemotherapy, transplant recipients or HIV carriers.

Ebola virus (EBOV).

Zoonotic disease: Fruit bats, apes (gorillas, chimpanzees), antelopes and monkeys.

Humans.

Contact transmission:

• Through direct contact (through broken skin or mucous membranes in, for example, the eyes, nose, or mouth) of a person who is sick with or has died from Ebola.
• Through direct contact with infected fruit bats, apes, monkeys and duikers.
• People remain infectious as long as their blood or body fluids contain the virus.
• Transmission after exposure to body fluids of immune-protected sites: the virus can remain in areas of the body that are protected from the immune system, even after the person has recovered. This includes the testes, inside of the eyes, placenta and central nervous system (particularly the fluid around the spinal cord and brain). There have been several “resurgence” outbreaks of EVD up to five years after the primary epidemic. Scientists are now studying how long the virus can stay in these immune-protected areas of the body, and how EVD resurgence may present in patients and/or be prevented.

Sexual transmission:

• Unsafe sex (oral, vaginal or anal) with male survivors presents additional risks for a specific period of time. The World Health Organization (WHO) recommends that male survivors of EVD practise safer sex for 12 months from onset of symptoms or until their semen tests negative twice for Ebola virus. There is no evidence that Ebola can be spread through sex or other contact with vaginal fluids from a woman who has recovered from Ebola.

Vehicle-borne transmission:

• Through contact with objects (like needles, medical equipment, bedding, clothing, dishes) that have been contaminated with blood or other body fluids from a person who is sick with Ebola, or through contact with the body of a person who has died from Ebola.

On average 8 to10 days (range 2—21 days).

People remain infectious as long as their blood contains the virus. Recovering patients are no longer contagious to others and their return home or transfer to a general hospital is safe. Breast milk may still be contagious for up to one month after recovery and sperm for up to nine months after the patient’s recovery.

• Starts with sudden fever, fatigue, muscle pain, headache and sore throat.
• Followed by vomiting, diarrhoea, rash, symptoms of impaired kidney and liver function. There may also be bleeding under the skin, from the nose and from the gums, blood with coughing, and blood in the stools.

• Other haemorrhagic fevers (Marburg haemorrhagic fever, Rift Valley fever, Crimean-Congo fever, Lassa fever)
• dengue fever
• yellow fever
• malaria
• typhoid fever
• meningitis.

• Antibody-capture enzyme-linked immunosorbent assay (ELISA).
• Antigen-capture detection tests.
• Serum neutralization test.
• Reverse transcription polymerase chain reaction (RT-PCR) assay.
• Electron microscopy.
• Virus isolation by cell culture.

Please refer to the appropriate local or international guidelines for clinical management. All clinical management including the administration of any treatment or vaccine should be conducted by  health professionals.

• A prompt isolation of probable and confirmed Ebola cases is required.
• Supportive care-rehydration with oral or intravenous (IV) fluids and treatment of specific symptoms improves survival.
• Specific treatments are available to treat infection with the Zaire strain of Ebola virus.

There are two licenced Ebola vaccines, typically used as follows:

• Ervebo, a single-dose vaccine against Zaire Ebola virus. SAGE currently recommends off-label use of the vaccine in outbreak settings for adults, infants and children from birth to 17 years of age, and for pregnant and lactating women. This vaccine is typically used in a ring vaccination strategy (contacts, contacts of contacts, and frontline workers), for anyone who has not been vaccinated with this vaccine in the preceding six months.

• Zabdeno and Mvabea is a two-dose vaccine for people aged one year and older, prioritized for preparedness areas, and for people who do not fall into the ring vaccination strategy above. As a two-dose regimen, it is not used for outbreak response, where immediate protection is needed.

People who recover from Ebola infection develop antibodies that last for at least ten years, possibly longer. It is not known if people who recover are immune for life or if they can become infected with a different species of Ebola.