WHO updates fact sheet on Ebola virus disease (19 June 2017)

The World Health Organization (WHO) has updated its fact sheet on Ebola virus disease (EVD).

Background Information:

The Ebola virus causes an acute, serious illness which is often fatal if untreated. Ebola virus disease (EVD) first appeared in 1976, with one of 2 outbreaks occurring in a village near the Ebola river- hence the name.

The virus family Filoviridae includes three genera:

  • Cuevavirus,
  • Marburgvirus, and
  • Ebolavirus.

Within the genus Ebolavirus, five species have been identified:

  • Zaire,
  • Bundibugyo,
  • Sudan,
  • Reston and
  • Taï Forest.

The first three, Bundibugyo ebolavirus, Zaire ebolavirus, and Sudan ebolavirus have been associated with large outbreaks in Africa. The virus causing the 2014–2016 West African outbreak belongs to the Zaire ebolavirus species.

Key Messages:

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

Transmission

It is thought that fruit bats of the Pteropodidae family are natural Ebola virus hosts.

Ebola is introduced into the human population through close contact with the blood, secretions, organs or other bodily fluids of infected animals such as

  • chimpanzees,
  • gorillas,
  • fruit bats,
  • monkeys,
  • forest antelope and
  • porcupines

found ill or dead or in the rainforest.

Ebola then spreads through human-to-human transmission via

  • direct contact (through broken skin or mucous membranes) with the blood, secretions, organs or other bodily fluids of infected people, and
  • with surfaces and materials (e.g. bedding, clothing) contaminated with these fluids.

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.

Burial ceremonies that involve direct contact with the body of the deceased can also contribute in the transmission of Ebola.

People remain infectious as long as their blood contains the virus.

Sexual Transmission

All Ebola survivors and their sexual partners should receive counselling to ensure safe sexual practices until their semen has twice tested negative. Survivors should be provided with condoms.

Male Ebola survivors should be offered semen testing at 3 months after onset of disease, and then, for those who test positive, every month thereafter until their semen tests negative for virus twice by RT-PCR, with an interval of one week between tests.

Ebola survivors and their sexual partners should either:

  • abstain from all types of sex, or
  • observe safe sex through correct and consistent condom use until their semen has twice tested negative.

Having tested negative, survivors can safely resume normal sexual practices without fear of Ebola virus transmission.

Clinical Features

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

Humans are not infectious until they develop symptoms.

First symptoms are the sudden onset of

  • fever,
  • fatigue,
  • muscle pain,
  • headache and
  • sore throat.

This is followed by

  • vomiting,
  • diarrhoea,
  • rash,
  • symptoms of impaired kidney and liver function, and in some cases,
  • both internal and external bleeding (e.g. oozing from the gums, blood in the stools).

Laboratory findings include low white blood cell and platelet counts and elevated liver enzymes.

The average EVD case fatality rate is around 50%. Case fatality rates have varied from 25% to 90% in past outbreaks

Diagnosis

Current WHO recommended tests include:

  • Automated or semi-automated nucleic acid tests (NAT) for routine diagnostic management.
  • Rapid antigen detection tests for use in remote settings where NATs are not readily available. These tests are recommended for screening purposes as part of surveillance activities, however reactive tests should be confirmed with NATs.

The preferred specimens for diagnosis include:

  • Whole blood collected in ethylenediaminetetraacetic acid (EDTA) from live patients exhibiting symptoms.
  • Oral fluid specimen stored in universal transport medium collected from deceased patients or when blood collection is not possible.

Samples collected from patients are an extreme biohazard risk; laboratory testing on non-inactivated samples should be conducted under maximum biological containment conditions. All biological specimens should be packaged using the triple packaging system when transported nationally and internationally.

Treatment 

Supportive care-rehydration with oral or intravenous fluids- and treatment of specific symptoms, improves survival.

There is as yet no proven treatment available for EVD. However, a range of potential treatments including blood products, immune therapies and drug therapies are currently being evaluated.

Prevention and Control

Outbreak control involves

  • Case management
  • Surveillance and contact tracing
  • Good laboratory service
  • Safe burials
  • Social mobilization

Health-care workers should always take standard precautions when caring for patients, regardless of their presumed diagnosis. These include

  • basic hand hygiene,
  • respiratory hygiene,
  • use of personal protective equipment (to block 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 extra infection control measures to prevent contact with the patient’s blood and body fluids and contaminated surfaces or materials such as clothing and bedding.

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 humans and animals for investigation of Ebola infection should be handled by trained staff and processed in suitably equipped laboratories.

Useful Links:

Link to the updated fact sheet:

http://who.int/mediacentre/factsheets/fs103/en/

Link to technical information on Ebola:

http://who.int/csr/resources/publications/ebola/infection-prevention/en/

Link to WHOs Frequently Asked Questions page on Ebola:

http://who.int/csr/disease/ebola/faq-ebola/en/

Link to WHO publications on Ebola:

http://who.int/csr/resources/publications/ebola/en/

Link to WHO publications on case management, infection prevention and control:

http://who.int/csr/resources/publications/ebola/infection-prevention/en/

Link to WHO document on clinical care for survivors of ebola:

http://who.int/csr/resources/publications/ebola/guidance-survivors/en/