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Monday, March 24, 2014

Is Ebola Coming To America?

The deadly Ebola virus has again struck the human race and attracted media attention in it's wake, particularly in the United States. For many, simply hearing or reading about Ebola evokes an uncomfortable and fearful feeling, partly due to media attention and movies like Outbreak but mostly because of the mystery that surrounds it. 

Is this virus as threatening to us as we make it out to be?

The Ebola virus likely begins it's life in African caves and mines within the bodies of fruit bats. Epidemics seem to begin when a single farmer or miner comes into contact with the infected animal. After seven days of incubation (virus making millions of copies of itself), the man develops sudden flu-like symptoms (headache, body ache, fever) and severe diarrhea that rapidly progress to cell death (necrosis), multi-organ failure, shock, widespread bleeding and, in many cases, death. Often, hospital staff or family members also become infected through contact with the patient's bodily fluids. 

Every couple of years, Ebola cuts through the middle of Africa like a knife, killing up to 88% of those it infects. It's monitored closely by the Center for Disease Control (CDC) for two important reasons: it easily spreads through the air (aerosol) and kills more than half of those it infects (high mortality rate). This is a harrowing combination for a virus but, despite it's label as a biosafety level 4 pathogen, it's currently not very threatening to the human race. Good sterilization and isolation processes help prevent rapid and deadly spread.

It's the fear of the unknown, though, that keeps scientists wary.

Ebola's lethal potential is recognizable in non-human primates: the virus has caused massive die-offs in gorilla and chimpanzee groups. It seems that the primates produce more infectious aerosol particles than do humans, attributing to the lethality. Luckily, these primate infections rarely spread to humans: only 25 human cases have been acquired from monkeys, with seven ending in death. The typical infection transmitted to humans from primates is more on par with a common cold. If this virus were to acquire the same virulence (or lethality) in humans as in monkeys, the results would be catastrophic. For now, however, it seems that Ebola is a manageable illness with little threat to the Americas.

  • There are five known species of Ebola, each named for the regions where they were originally identified.  The first reported cases in 1967 included 550 humans in Zaire and Sudan. The Zaire Ebola virus recurred in Gabon in 1994, causing 317 cases. The Sudan Ebola species returned in 2004, but this time in Uganda, killing 224 (53%) of 425 patients. 
  • The inflammatory response caused by the virus often leads to the body losing all it's platelets (used to plug holes), resulting in bleeding through multiple orifices.  It is for this reason it is known as a "hemorrhagic fever"
  • A new Ebola vaccine has been developed, but low funding has halted human trials. It may be as long as 20 years before the vaccine is commercially available. 


Peters CJ. Chapter 197. Ebola and Marburg Viruses. In: Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson J, Loscalzo J. eds. Harrison's Principles of Internal Medicine, 18e. New York: McGraw-Hill; 2012. Accessed March 22, 2014.