Ebola virus disease (EVD), which was formerly known as Ebola haemorrhagic fever first came to the attention of health professionals in 1976 after two simultaneous outbreaks occurred in Sudan and the Democratic Republic of Congo.
In the Democratic Republic of Congo, formerly known as Zaire, a sudden outbreak of disease occurred. The disease caused fever, rashes, and internal bleeding and moved along the banks of the Ebola River for a time, before it disappeared as suddenly as it had appeared. The virus was named after the river, and the strain named after the country.
Ebola virus disease is severe and often lethal in humans, with a death rate as high as 90 percent.
There are five strains of Ebola:
- Bundibugyo ebolavirus (BDBV)
- Zaire ebolavirus (EBOV)
- Reston ebolavirus (RESTV)
- Sudan ebolavirus (SUDV)
- Tai Forest ebolavirus (TAFV)
Bundibugyo ebolavirus, Zaire ebolavirus and Reston ebolavirus are all members of the Filoviridae family (filovirus). The virus is an RNA virus.
Ebola virus is transmitted through humans and animals, specifically primates and fruit bats. Infected animals can transmit the virus to humans, where it is then passed onto others via human to human transmission. Transmission between humans occurs through close contact with infected blood, bodily fluids, organs and other secretions. Direct contact, through broken skin or mucous membranes with these fluids spreads the infection. People are infectious for as long as their blood and fluids contain the virus. The virus can also be transmitted via the semen of men who have been infected for up to seven weeks after recovery. The incubation period for Ebola is 2 to 21 days.
Symptoms of Ebola virus include sudden onset headache, fever, sore throat, muscle pain and intense weakness. Following these initial symptoms, vomiting, diarrhoea, impaired liver and kidney function are usually present. In some cases there is also both internal and external bleeding. Low white cell count and elevated liver enzyme levels are also present when laboratory testing is conducted.
There are a number of laboratory tests used in diagnosing Ebola virus. Once other illnesses, such as cholera, malaria, typhoid fever, meningitis, plague, hepatitis and other haemorrhagic fevers have been ruled out, tests such as antibody-capture enzyme-linked immunosorbent assay (ELISA), antigen detection tests, virus isolation by cell culture, electron microscopy, serum neutralization, reverse transcriptase polymerase chain reaction (RT-PCR) assay are used for a definitive diagnosis of Ebola virus.
There was no vaccine for Ebola virus at the beginning of the West African Ebola Outbreak, and no treatment specifically for the virus either. Treatment in Ebola patients usually comprises of intravenous or oral rehydration therapy.
Fruit bats, specifically the Hypsignathus monstrosus, Epomops franqueti and Myonycteris torquata species are believed to be the natural host of the virus, and when the West Africa Ebola Outbreak began, health officials warned those living within the affected communities to avoid coming into contact with the animals, or eating the undercooked or bloody meat of any animal capable of hosting the virus.