Aliases: Ebola hemorrhagic fever, Ebola virus disease, EVD, Ebola
Ebola virus disease (EVD) is one of the most virulent illnesses in the world, and the current outbreak is the largest ever recorded. As of July 30th, the Ebola epidemic had spread to include 4 countries in West Africa (Guinea, Liberia, Sierra Leone, and Nigeria), and there had been 1440 suspected and confirmed cases and 826 suspected case fatalities, amounting to a fatality rate of about 57%3 (for the latest update, here is the CDC outbreak site). In light of the seriousness of the situation, I thought it time for an exploration of the facts about this epidemic and the disease itself.
Where does Ebola come from?
Ebola outbreaks have occurred in waves since the disease was first identified in 1976 in the Democratic Republic of Congo, near the eponymous Ebola River1,3. While several animal species can carry the virus (see the Cause section below), they are thought to be accidental hosts, like humans. Although the natural host and disease reservoir remains unclear3, it currently considered to be fruit bats in the Pteropdidae family1. There are 5 species of Ebola virus, only 4 of which cause disease in humans1,3. The species vary widely in severity, with case fatality rates ranging from about 25% to 90%.
Why is this outbreak so bad?
The current Ebola epidemic is of the most lethal species, but that isn’t the only reason it has been so difficult to control. This is the first outbreak to occur in the affected region of West Africa, and medical professionals there were largely untrained for an Ebola epidemic. They were also short-staffed; there was a shortage of health workers on the ground. Most previous epidemics have happened in more rural areas, whereas this outbreak has struck fairly urbanized regions. With greater infrastructure comes greater travel, and people are better able to move the disease long distances, making potential cases harder to track2.
Fear has aided the disease. The belief that health workers are spreading the illness has made people unwilling to report cases. Relatives are also hesitant to report their loved ones for fear that they will be taken away to die alone. Compassion and cultural practices have also played a role; the care of sick relatives and funeral practices put the healthy at risk2.
Fear of the epidemic spreading to North America has ratcheted up with the return of Dr. Kent Brantly, an American aid worker, to the US for treatment after he contracted Ebola in Liberia. The CDC has been quick to nip these concerns in the bud, reiterating that 1. Ebola is not airborne, 2. Ebola is not waterborne, and 3. Ebola is controllable in US healthcare settings.
Cause: EVD is (re)introduced into human populations through close contact with the bodily fluids of infected animals (this can include gorillas, chimpanzees, monkeys, fruit bats, forest antelope, and porcupines). It is then transmitted from person to person by direct contact (through broken skin or mucous membranes) with the bodily fluids, such as blood, secretions, or semen, of an infected person. It may also be transmitted indirectly, through contact with a contaminated environment. Recovered patients can remain infectious long after they return to good health; the virus has been found in the semen of male patients up to 61 days after recovery1.
Consequence: After an incubation period (the time from exposure to the onset of symptoms) of 2 to 21 days, patients will initially experience fever, extreme weakness, headache, muscle pain, and sore throat. As the disease progresses, the sick will develop a rash, diarrhea, vomiting, impaired kidney and liver function, reduced white blood cell and platelet counts, and, in the most extreme cases, internal and external bleeding1.
Cure: There is no vaccine or treatment for EVD. Outbreaks are controlled using quarantine and other transmission prevention measures1,3.
1. Ebola virus disease. World Health Organization. April 2014. Web. 3 August 2014. http://www.who.int/mediacentre/factsheets/fs103/en/
2. Osterholm, MT. “Why it’s harder to contain this Ebola epidemic”. Chicago Tribune. 4 August 2014. Chicagotribune.com. Web. 3 August 2014.
3. Outbreak of Ebola in Guinea, Liberia, Sierra Leone. Centers for Disease Control and Prevention. 3 August 2014. Web. 3 August 2014. http://www.cdc.gov/vhf/ebola/outbreaks/guinea/index.html
Image source: Creative Commons, http://ceb.wikipedia.org/wiki/Pteropodidae