The Ebola Virus: An Overview

The 2014 West African Ebola outbreak was the largest Ebola outbreak in recorded history, with 21,832 cases in 9 countries resulting in a total of 8,710 deaths. But the Ebola virus is far from new. Ebola first appeared in a pair of simultaneous outbreaks in Zaire in 1976, one in Nzara, Sudan, and the other in Yambuku, Democratic Republic of Congo. The Yambuku outbreak occurred in a village near the Ebola River, from which the virus takes its name.

Since 1976, there have been more than 20 separate outbreaks of the Ebola virus disease, which the World Health Organization abbreviates to "EVD." Mortality rates vary wildly from 25% to 90%, and the Zaire strain is largely regarded as the most deadly. The WHO puts the average mortality rate for this particular strain at 50%. To put things in perspective, the 1918 Spanish Flu pandemic that killed an estimated 50-100 million people only had a mortality rate of 10-20%.

Ebola is a philovirus, a microscopic organism with a shepherd's-hook-like appearance. Despite it's dangerous reputation and fear-inducing ability, the tiny virus is only about one-sixth as long as a human hair is wide. Of the five different strains of Ebola – Zaire, Sudan, Bundibugyo, Tai Forest, and Reston – only the Reston strain is not deadly to humans (as far as we know). Ebola functions much the same way as other viruses, waiting in a host organism and searching for vulnerable cells to infect. For Ebola, the wait is short; the virus can and will infect a broad range of cell types. The initial infection occurs in cells associated with our immune system – namely monocytes, macrophages and dendritic cells. As the infection progresses, Ebola moves along to the liver, spleen, and lymph nodes through the bloodstream.

Many people assume that Ebola leads immediately to hemorrhagic bleeding from multiple orifices; while this isn't necessarily untrue, it's certainly not the norm. Ebola's incubation period, i.e. the amount of time it takes for an infected person to become symptomatic, is 2-21 days. However, most patients are symptomatic by day 10. Initially, symptoms are mild enough to be mistaken for the flu. They include fever, headache, chills, muscle and joint aches, and fatigue. As the disease progresses the symptoms become more severe, resulting in loss of appetite, painful sore throat, bloody diarrhea, and vomiting. Roughly half of Ebola patients develop a severe rash by about the five-day mark. Late-stage Ebola causes massive internal hemorrhaging, depleting the supply of proteins that produce blood clots. This results in uncontrolled bleeding, hemorrhage shock, and ultimately multi-organ failure. Organ failure is what typically makes the disease fatal, causing death between 6-16 days after onset of symptoms.

Historically, Ebola occurred primarily in Africa and was relatively uncommon, sometimes disappearing for decades. In addition, Ebola's high mortality rate requires the use of high-security Biosafety Level (BSL) 4 labs when handling the virus. These facts have long stifled large-scale research. The 2014 outbreak spurred intense efforts on the part of health organizations, resulting in an experimental drug called ZMapp. Doctors used ZMapp to successfully treat several patients, but unfortunately, production and development of the drug dwindled significantly following the outbreak. The WHO has declared the 2014 West African Outbreak over, but the world hasn't forgotten; Ebola-related news is still making headlines. The first experimental vaccine for the virus is en route to West Africa for testing, bringing hope that the world will have a stronger defense the next time Ebola rears its tiny, ugly head.


World Health Organization
U.S. Center for Disease Control: Ebola Outbreaks
U.S. Center for Disease Control: Ebola Treatment
Health: How Stuff Works
Science: How Stuff Works
The New York Times

About the Author
Iris Stone began her working as a freelance writer and researcher in 2011. Her business soon took off and she now owns and operates a writing and editing firm that works with clients all across the country. Despite the time it takes to run a business she still does much of the writing herself, and her work has included a variety of content related to education, medicine, healthcare careers, and science. Her interests actually span far beyond writing, and she is currently studying to be a physicist! Check out her Google+ Profile.

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