Ebola virus disease (EVD) was previously known as Ebola haemorrhagic fever. It is a severe, often fatal disease in humans and nonhuman primates (monkeys, gorillas and chimpanzees).
EVD is caused by a virus, and first appeared in 1976 when two outbreaks (o ne in an area near the Ebola River in Democratic Republic of Congo, and the other in South Sud an) occurred. Since then, sporadic outbreaks have occurred, most commonly in the Democratic Republic of Congo, Uganda, South Sudan, Congo and Gabon.
The origin of Ebola virus is not known, but fruit bats are thought to be the likely host of the virus.
Ebola virus is thought to be transmitted to humans through direct contact with the blood, secretions, organs or other bodily fluids of infected animals (which include: chimpanzees, gorillas, bats, monkeys, forest antelope and porcupines). This occurs when hunters/ other persons come into contact with infected dead animals found lying in the rainforest, or handling raw meat of infected animals.
Once a person is infected, the Ebola virus can spread to other people in the community.
Infection occurs from direct contact (through broken skin or mucous membranes, including the nose, eyes and mouth) with blood, or other bodily fluids and secretions (including stool, urine, saliva, semen) of infected people. Less commonly, infection can also occur from direct contact (through broken skin, or mucous membranes –including the nose, eyes and mouth) with environments that are contaminated with an Ebola patient’s infectious blood or body fluids, such as soiled clothing, bed linen, or used needles. Burial ceremonies in which mourners have direct contact with the body of the deceased person have also been responsible for spreading infection in some outbreaks. Ebola virus is not spread in the air, so simply being in the same room as an infected person without having the kinds of contact detailed above is not a risk for infection.
During EVD outbreaks, the following persons are most at risk for infection:
After infection with the Ebola virus, there is an incubation period of 2 – 21 days (on average, 8-10 days) after which the person will start to experience symptoms. During the incubation period, the person is well and shows no signs of being infected. After the incubation period, the initial symptoms include fever, weakness and lethargy, muscle pain, headache and sometimes sore throat. This is followed by vomiting, diarrhoea, abdominal pain, and sometimes a rash. Some patients may experience bleeding inside and outside of the body; this is the most serious complication.
EVD can only be confirmed through laboratory testing, usually a blood test. A specialised laboratory at the National Institute for Communicable Diseases in Johannesburg is able to test for Ebola virus disease. EVD can only be diagnosed once a person develops signs and symptoms of the disease; there is no test available to detect infection whilst a person is still in the incubation period of disease.
There is no medication available to treat the Ebola virus itself. Standard treatment for EVD is limited to supportive therapy, and severely ill patients require intensive supportive care. This consists of balancing the patient’s fluids and electrolytes, maintaining their oxygen status and blood pressure, and treating them early for any complicating infections.
Some patients will recover with the appropriate medical care. In previous EVD outbreaks, 50-90% of Ebola patients have died. In the current EVD outbreak in West Africa, about 60% of Ebola patients have died.
To control further spread of Ebola virus, patients that are suspected to have EVD should be isolated from other patients and treated by healthcare workers using very strict precautions to prevent being infected.
Experimental treatment has been tested in animal models, but has not yet been used in humans.
There is no licensed vaccine for EVD. Several vaccines are being tested, but none are available for clinical use as yet. Preventing initial cases is challenging, since it is still not known how exactly Ebola virus is maintained in nature and what preventive interventions would be successful.
Once an initial case of EVD occurs in a community, preventing spread to other people is critical. This includes educating the general public about the disease and how it can be prevented from spreading further.
Healthcare workers are at high risk of exposure to the virus when caring for Ebola patients, and need to apply additional infection control precautions over and above the standard healthcare precautions. This includes wearing personal protective equipment (including gloves, masks, gowns and goggles), ensuring complete equipment sterilisation, and the routine use of disinfectant. Infected patients must be isolated from other patients and cared for by staff who are trained in the appropriate infection control measures.
The World Health Organization regularly reviews the public health situation and recommends any travel or trade restrictions. At present, no travel or trade restrictions are recommended.
The risk of infection for travellers is very low, even if the visit included travel to the local areas from which primary cases have been reported. Infection with Ebola virus requires direct contact with blood, secretions, organs or other body fluids of infected living or dead persons or animals, all of which are unlikely exposures for the average traveller.
There is no risk of Ebola virus transmission during the incubation period and only low risk of transmission in the early phase of disease. Historically, several cases of haemorrhagic fever (Ebola, Marburg, Lassa, Crimean‐Congo haemorrhagic fever) disease were diagnosed after long‐ distance travel but none developed the symptoms during the international travel and no persons who came into contact with the patients during travel were infected.
Travellers must have a valid yellow fever vaccination certificate when travelling to Guinea, Liberia, or Sierra Leone.
Since these countries are risk areas for malaria, travellers should consult a healthcare professional regarding the appropriate malaria prophylaxis that needs to be taken. Malaria is the most likely cause of illness with fever in a person who has travelled to West Africa, so travellers must pay particular attention to malaria prevention.
The symptoms of early EVD are the same as many other infections that can be acquired in West Africa, including malaria, dengue fever, Lassa fever, and typhoid fever. Travellers should take routine precautions to prevent such infections, including: malaria prophylaxis, preventing mosquito bites, regular hand washing with clean water and soap, and adhering to safe water and food practices.