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Numbers, STEM

NUMBERS: Ebola Virus Disease (EVD)

Image of the Ebola Virus, Source: CDC

Image of the Ebola Virus, Source: CDC

There’s been no shortage of news stories during the second half of 2014. Staying current on topics of interest has proven challenging given my very compressed schedule of the last three months. Included in all of these events is the first detection of the Ebola virus disease (EVD) in the United States.

On September 20th, Ebola made a 5,700-mile trip to the U.S., when a Liberian man, Thomas Eric Duncan, flew to Dallas, TX. His infection was confirmed on September 30th. Two nurses who cared for him before he died now have the disease. [Ref 1] The finger pointing has gone beyond good health care and prevention to political posturing and scare tactics. As one news analyst reported, “the politics of fear has shown up in a big way”.

While these gestures revealed how poorly prepared some divisions of the U.S. health care sector are in addressing a potentially deadly virus, laying blame and finger pointing did not make one person healthier or safer. It also tells us that when something is new, it creates a new type of fear that overshadows other serious issues or diseases that we have been living with for some time. This short post discusses the origins of the Ebola virus and how it is transmitted in the human population, and shows the number of cases that have been diagnosed since its inception and where.

According to the World Health Organization (WHO), EVD first appeared in 1976 in two simultaneous outbreaks: Nzara, Sudan and Yambuku, Democratic Republic of Congo. The latter occurred in a village near the Ebola River from which the disease takes its name. The Ebola virus causes an acute serious illness that can often be fatal if untreated.

Table 1: Chronology of Previous EVD Outbreaks*


The first EVD outbreaks occurred in remote villages in central Africa, near tropical rainforests. Between 1976 and 2012, the most cases of EVD (425) that were diagnosed in any given year during this period occurred in the country of Uganda in 2000. As shown in Table 1, the virus has been restricted to countries in Africa during this time. However, the most current outbreak in west Africa (first cases reported in March 2014), is the largest and most complex Ebola outbreak since EVD was first discovered in 1976. [Ref 1]

As of October 17th, EVD has infected more than 9,200 persons and killed more than 4,500. With cases being reported in both the U.S. and Europe, the disease has yet to be brought under control.


How is the virus transmitted? Researchers at WHO and other organizations have traced the origins of the disease to the fruit bats of the Pteropodidae family. The bats are considered to be natural Ebola virus hosts. Ebola is introduced into the human population through close contact with the blood, secretions, organs or other bodily fluids of infected animals such as chimpanzees, gorillas, fruit bats, monkeys, forest antelope and porcupines found ill or dead or in the rainforest.

Ebola then spreads through human-to-human transmission via direct contact (through broken skin or mucous membranes) with the blood, secretions, organs or other bodily fluids of infected people, and with surfaces and materials (e.g. bedding, clothing) contaminated with these fluids. Health-care workers have frequently been infected while treating patients with suspected or confirmed EVD. This has occurred through close contact with patients when infection control precautions are not strictly practiced.

People remain infectious as long as their blood and body fluids, including semen and breast milk, contain the virus. Men who have recovered from the disease can still transmit the virus through their semen for up to 7 weeks after recovery from illness.

After the last two weeks of separating fact from fiction about EVD, many news outlets have come on board to do just that. This morning, Chuck Todd, host of NBC’s Meet the Press, hosted an Ebola Summit with a distinguished panel of guests to scrub the facts on this topic. It also appears that just about every other Sunday news show on television covered some aspect of EVD and what the U.S. and other countries are and/or should be doing.

My next post on EVD will discuss the differences between an outbreak, an epidemic, and a pandemic and good hygiene practices that each of us should include in our daily routine to stay healthy from not just EVD, but other diseases and illnesses.


    1. Mission Unaccomplished: Containing Ebola in Africa, by Marilynn Marchione for the Associated Press, October 18, 2014.

About Vi Brown

Vi is principal and CEO of Prophecy Consulting Group, LLC, an Arizona firm that provides business and engineering services to private and public clients. Prior to establishing her consulting practice in 2001, Vi worked with Motorola, Maricopa County Government, Pacific Gas & Electric, CH2M Hill, and Procter & Gamble. As an adjunct faculty member, Vi teaches undergraduate calculus classes and graduate level environmental courses. She is also a professional speaker.

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