Ebola virus disease, formerly known as Ebola hemorrhagic fever, is often referred to by the general public as “Ebola”, which is a rare but often fatal illness affecting humans and non-human primates such as gorillas, monkeys, and chimpanzees. However, this deadly disease is actually caused by a group of viruses within the genus Ebolavirus. These viruses are the Ebola virus, Sudan virus, Tai Forest virus, Bundibugyo virus, Reston virus, and Bombali virus. Of these viruses, only the Ebola virus, Sudan virus, Tai Forest, and Bundibugyo viruses are known to cause disease in people.
The Ebola virus was first discovered in 1976 near the Ebola River, which is located in the Democratic Republic of the Congo. Scientists are not sure where the Ebola virus came from but believe the virus is animal-borne and that bats are the most likely source1.
How is the disease transmitted?
The Ebola virus disease is spread to people through direct contact with bodily fluids such as blood from an infected person. The virus gets in through broken skin or mucous membranes located in the eyes, nose, or mouth. The virus can also be transmitted through sexual contact1. At this time, all body fluids such as blood, urine, emesis (vomit), stool, and semen can contain the virus. Furthermore, there is no evidence of the Ebola virus being transmitted either the environment or fomites that could have become contaminated during patient care such as bed rails, doorknobs, or laundry2.
Where has the disease spread?
The Ebola virus disease has been reported mostly in Africa in areas such as the Democratic Republic of the Congo, Uganda, South Sudan, Republic of Congo, Gabon, Cote d’Ivoire (Ivory Coast), Guinea, Sierra Leone, and Liberia. The largest outbreak to date occurred from 2014 to 2016 in West Africa. There was one case reported in England in 1976 from a contaminated needle, one case in Russia from a laboratory worker injecting the virus accidentally in 2004, one case in Spain due to human-to-human transmission that resulted in an infected healthcare worker, and four cases in the United States from 2014 to 2016 that included two nurses who cared for infected patients1.
What are the signs and symptoms?
Symptoms can appear anywhere from 2 to 21 days after contact with the virus but usually occur on average of 8 to 10 days1. The World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) have established criteria for making a diagnosis that include the sudden onset of a high fever and at least 3 of the following: headache, vomiting, loss of appetite, diarrhea, stomach pain, muscle aches or joint pain, difficulty swallowing, trouble breathing, or hiccuping. The Ebola virus disease is not contagious until infected patients become symptomatic2.
How is the diagnosis made?
Diagnosing the deadly disease can be difficult. However, blood samples from the patient are collected and tested to confirm infection1. There are multiple serologic tests to confirm the diagnosis but because of the associated biohazards there are only a few laboratories in the world that can safely perform them2.
What is the treatment for Ebola?
Unfortunately, there is no specific treatment for the Ebola virus disease. Interventions include providing fluids and electrolytes, oxygen therapy as needed, and medication to reduce fevers, vomiting, pain, or diarrhea1. There is an investigational vaccine called rVSV-ZEBOV that has shown to be safe and protective against the Zaire strain of the Ebolavirus. This vaccine is being used in the ongoing 2018-2019 Ebola outbreak in the Democratic Republic of the Congo3. There is also another Ebola vaccine candidate- the recombinant adenovirus type-5 Ebola vaccine. This vaccine was evaluated in a phase II trial in Sierra Leone in 2015 and research is still ongoing1. Another promising therapy is with monoclonal antibodies such as ZMapp. This has been shown to reverse infection in nonhuman primates, and to cure infected animals after symptoms and the circulating Ebola virus are present.
There are no predictors of survival. However, some studies done in nonhuman primates indicate that the greater the viral exposure and the shorter the incubation period then the greater likelihood of death2. The average case does have a fatality rate around 50 percent but has varied from 25 percent to 90 percent in past outbreaks4.