Ebola virus disease
Key facts * Ebola virus disease (EVD), formerly known as Ebola haemorrhagic fever, is a severe, often fatal illness in humans. * The virus is transmitted to people from wild animals and spreads in the human population through human-to-human transmission. * The average EVD case fatality rate is around 50%. Case fatality rates have varied from 25% to 90% in past outbreaks. * The first EVD outbreaks occurred in remote villages in Central Africa, near tropical rainforests, but the most recent outbreak in west Africa has involved major urban as well as rural areas. * Community engagement is key to successfully controlling outbreaks. Good outbreak control relies on applying a package of interventions, namely case management, surveillance and contact tracing, a good laboratory service, safe burials and social mobilisation. * Early supportive care with rehydration, symptomatic treatment improves survival. There is as yet no licensed treatment proven to neutralise the virus but a range of blood, immunological and drug therapies are under development. * There are currently no licensed Ebola vaccines but 2 potential candidates are undergoing evaluation.

Background
The Ebola virus causes an acute, serious illness which is often fatal if untreated. Ebola virus disease (EVD) first appeared in 1976 in 2 simultaneous outbreaks, one in Nzara, Sudan, and the other in Yambuku, Democratic Republic of Congo. The latter occurred in a village near the Ebola River, from which the disease takes its name.
The current outbreak in west Africa, (first cases notified in March 2014), is the largest and most complex Ebola outbreak since the Ebola virus was first discovered in 1976. There have been more cases and deaths in this outbreak than all others combined. It has also spread between countries starting in Guinea then spreading across land borders to Sierra Leone and Liberia, by air (1 traveller only) to Nigeria, and by land (1 traveller) to Senegal.
The most severely affected countries, Guinea, Sierra Leone and Liberia have very weak health systems, lacking human and infrastructural resources, having only recently emerged from long periods of conflict and instability. On August 8, the WHO Director-General declared this outbreak a Public Health Emergency of International Concern.
A separate, unrelated Ebola outbreak began in Boende, Equateur, an isolated part of the Democratic Republic of Congo.
The virus family Filoviridae includes 3 genera: Cuevavirus, Marburgvirus, and Ebolavirus. There are 5 species that have been identified: Zaire, Bundibugyo, Sudan, Reston and Taï Forest. The first 3, Bundibugyo ebolavirus, Zaire ebolavirus, and Sudan ebolavirus have been associated with large outbreaks in Africa. The virus causing the 2014 west African outbreak belongs to the Zaire species.
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 in which mourners have direct contact with the body of the deceased person can also play a role in the transmission of Ebola.
People remain infectious as long as their blood and body fluids, including semen and breast milk, contain the virus. Men who have recovered from the disease can still transmit the virus through their semen for up to 7 weeks after recovery from illness.
Symptoms of Ebola virus disease
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.
Diagnosis
It can be difficult to distinguish EVD from other infectious diseases such as malaria, typhoid fever and meningitis. Confirmation that symptoms are caused by Ebola virus infection are made using the following investigations: * antibody-capture enzyme-linked immunosorbent assay (ELISA) * antigen-capture 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; laboratory testing on non-inactivated samples should be conducted under maximum biological containment conditions.
Treatment and vaccines
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. No licensed vaccines are available yet, but 2 potential vaccines are undergoing human safety testing.
Prevention and control
Good outbreak control relies on applying a package of interventions, namely case management, surveillance and contact tracing, a good laboratory service, safe burials and social mobilisation. Community engagement is key to successfully controlling outbreaks. Raising awareness of risk factors for Ebola infection and protective measures 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 or monkeys/apes 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 at home. Regular hand washing is required after visiting patients in hospital, as well as after taking care of patients at home. * Outbreak containment measures including prompt and safe burial of the dead, identifying people who may have been in contact with someone infected with Ebola, monitoring the health of contacts for 21 days, the importance of separating the healthy from the sick to prevent further spread, the importance of good hygiene and maintaining a clean environment.
Controlling infection in health-care settings:
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.
WHO response
WHO aims to prevent Ebola outbreaks by maintaining surveillance for Ebola virus disease and supporting at-risk countries to developed preparedness plans. The document provides overall guidance for control of Ebola and Marburg virus outbreaks: * Ebola and Marburg virus disease epidemics: preparedness, alert, control, and evaluation
When an outbreak is detected WHO responds by supporting surveillance, community engagement, case management, laboratory services, contact tracing, infection control, logistical support and training and assistance with safe burial practices.
WHO has developed detailed advice on Ebola infection prevention and control: * Infection prevention and control guidance for care of patients with suspected or confirmed Filovirus haemorrhagic fever in health-care settings, with focus on Ebola
What this – the largest Ebola outbreak in history – tells the world
What does this outbreak, that has been making media headlines for months, tell us about the state of the world at large? What does it tell world leaders, and the citizens who elect them, about the state and status of public health?
WHO Director-General, Dr Margaret Chan, sees six specific things.
First, the outbreak spotlights the dangers of the world’s growing social and economic inequalities. The rich get the best care. The poor are left to die.
Second, rumours and panic are spreading faster than the virus. And this costs money. Ebola sparks nearly universal fear. Fear vastly amplifies social disruption and economic losses well beyond the outbreak zones.
The World Bank estimates that the vast majority of economic losses during any outbreak arise from the uncoordinated and irrational efforts of the public to avoid infection.
Third, when a deadly and dreaded virus hits the destitute and spirals out of control, the whole world is put at risk. Our 21st century societies are interconnected, interdependent and electronically wired together as never before.
This became clear when the virus entered Nigeria’s oil and natural gas hub, the city of Port Harcourt. Nigeria is the world’s fourth largest oil producer and second largest supplier of natural gas. If that outbreak flares up again, it could dampen the economic outlook worldwide.
Fourth, decades of neglect of fundamental health systems and services mean that a shock, like an extreme weather event or a disease run wild, can bring a fragile country to its knees.
These systems cannot be built up during a crisis. Instead, they collapse. A dysfunctional health system also means zero population resilience to the range of shocks that our world is delivering, with ever greater frequency and force – whether from a changing climate, armed violence and civil unrest, or a deadly and dreaded virus.
Deadly pathogens exploit weak health systems
WHO is aware that, in the three hardest-hit countries, high numbers of deaths from other causes are occurring, whether from malaria and other infectious diseases, or zero capacity for safe childbirth.
The size of this “emergency within the emergency” is not precisely known, as systems for monitoring health statistics – not good to begin with – have now broken down completely.
It is, however, important to understand one point: these deaths are not “collateral damage”. They are all part of the central problem: no fundamental public health infrastructures were in place, and this is what allowed the virus to spiral out of control.
In the simplest terms, this outbreak shows how one of the deadliest pathogens on earth can exploit any weakness in the health infrastructure, be it inadequate numbers of health care staff or the virtual absence of isolation wards and intensive care facilities throughout much of sub-Saharan Africa.
WHO has been making these arguments for at least two decades. Some signs are beginning to suggest that they are now falling on more receptive ears.
When presidents and prime ministers in non-affected countries make statements about Ebola, they rightly attribute the outbreak’s unprecedented spread and severity to the “failure to put basic public health infrastructures in place”.
No incentive for research
A fifth especially striking issue is this: Ebola emerged nearly 40 years ago. Why are clinicians still empty-handed, with no vaccines and no cure? Answer: because Ebola has been, historically, geographically confined to poor African nations.
The R&D incentive is virtually non-existent. A profit-driven industry does not invest in products for markets that cannot pay.
Again, WHO has been trying to make this issue visible for more than a decade, most recently through the deliberations of the Consultative Expert Working Group on Research and Development: Financing and Coordination.
Now people see the reality of this R&D failure, this market failure, on TV screens and in the headline news: the world’s empty-handed clinicians in their hazmat suits, trying to help Africa’s desperate poor, putting their own lives at risk, and losing them.
Fast action on new therapies and vaccines
On the issue of experimental therapies and vaccines, WHO has moved fast in securing ethical approval and coordinating worldwide collaborative efforts to move the most promising products forward.
Three weeks ago, the Organization brought together more than 100 of the world’s leading experts on the many complex issues surrounding the use of these experimental medical products. As a result, this could be the first Ebola outbreak in history that can be tackled with vaccines and medicines.
For vaccines, testing on human volunteers has already begun. If all continues to go well, 2 vaccines could be ready for progressive introduction near the end of this year. Some 5 to 10 drugs are also being developed as quickly and safely as possible.
For vaccines, the projected year-end quantities are considered large enough to have at least some impact on the future of the outbreak’s evolution.
Blood from survivors holds hope
The experts also debated the pros and cons of treating Ebola patients with transfusions of whole blood taken from patients who survived their infection. This form of treatment has been used empirically in the past, in a small group of patients, with promising results.
Convalescent plasma was also considered as an alternative treatment option. Of the two options, use of convalescent plasma is technically more complex and more demanding in terms of facilities and skills. The eventual use of this experimental therapy in Guinea, Sierra Leone and the Democratic Republic of Congo will depend on the availability of skilled technical expertise.
The experts decided that both treatment options should be prioritized for further investigation. WHO is already in discussions with health experts in the Democratic Republic of Congo, Guinea, Liberia, Nigeria and Sierra Leone. These joint discussions are currently looking at the practicalities of using whole blood transfusions and convalescent plasma from survivors.
Finally, the world is ill-prepared to respond to any severe, sustained and threatening public health emergency. That statement was one of the main conclusions of the Review Committee convened, under the provisions of the International Health Regulations, to assess the response to the 2009 influenza pandemic.
The Ebola outbreak proves, beyond any shadow of a doubt, that this conclusion was spot on.

http://www.who.int/mediacentre/factsheets/fs103/en/
http://www.who.int/csr/disease/ebola/ebola-6-months/lessons/en/