Let's Crash Course the Ebola Virus: Medical Student Edition

By Joe Savarese

Lets Crash Course the Ebola Virus - Medical Student EditionUnless you truly have been living in a hole studying for exams, you have probably noticed that the media has run daily headlines about Ebola scares and fears of future epidemics. So I thought, as a medical student, what should I know about Ebola if a friend, relative, or patient asked for information? (or what if it showed on an USMLE exam?)

Here’s the crash course..

The Ebola Virus is part of the Filoviridae family, meaning it’s a helical single-stranded negative-sense RNA strand. (Remember a negative-stranded virus must carry with it a RNA-dependent RNA polymerase for infectivity).

Marburg virus is in the same class and is very similar to Ebola since both present as fatal hemorrhagic fevers. The Marburg virus has a natural reservoir in monkeys, while unknown in the Ebola virus, it is believed to be in bats. Most outbreaks of Ebola thus far have occurred in Sub-Saharan Africa such as Uganda and the Democratic Republic of the Congo.

Signs, Symptoms, and Diagnosis

The CDC has listed on their website symptoms of Ebola including fever, headache, muscle pain, weakness, diarrhea, vomiting, abdominal pain, and unexplained bruising and bleeding. Symptoms may appear from 2 to 21 days after exposure. After flu-like symptoms appear, infection continues to other organs such as the brain, kidney, and intestines leading to third spacing, shock, and hemorrhagic findings.

In general, transmission is by similar routes as HIV – bodily fluids, needle sharing, and infected animals. However, there has been no evidence of sexual transmission of Ebola even when RNA levels are detected in the semen (cdc.gov). The virus is not transmitted through air or water. Obviously, due to lack of patients, studies have been limited in this field. Click here for more information on transmission from the CDC.

Ebola is detectable through measuring RNA blood levels, which are near threshold or low when symptoms and fever first develop making it difficult and unreliable to have a positive test before fever. Symptoms of Ebola are also very nonspecific, which makes early diagnosis difficult.

It should be no surprise that for testing, ELISA method and PCR are used. (Couldn’t hurt to brush up on these methods here and here.


Supportive care. Currently, several companies are working to develop a vaccine. One product called ZMapp that may enter Phase 1 drug testing soon uses monoclonal antibodies for treatment (it was already used on two Americans). Serum from survivors might be used because of the formed antibodies that might be key to fight the infection.


Isolation from infected individuals. Interestingly enough, about a year ago, some studies showed in mice that Selective Estrogen Receptor Modulators (SERMs) like clomiphene may prevent the viral fusion of the Ebola virus. (Here’s the article for your ID pimp sessions.)

Practice Case:

A 42-year-old Ugandan patient with a 4-day history of fever, maculopapular rash, elevated liver enzymes, and thrombocytopenia is found to have positive serological studies indicating Ebola infection. After analysis of the RNA genome, the virus is found to have a point mutation when compared to another patient that was isolated in another region of Uganda. What genetic phenomenon mostly likely occurred that may lead to a future epidemic?

a. Genetic shift
b. Genetic drift
c. Reassortment
d. Phenotypic mixing
e. Specialized Transduction

Put your answer in the comment section!

Categories: Miscellaneous

13 replies »

  1. It should be antigenic drift for epidemics
    Antigenic drift is shown by Influenza A, B, C and HIV
    Antigenic shift is only shown by Influenza A


  2. Also hiccups are very characteristic finding
    It can be transmitted even after the death of a person with Ebola
    Best measures for protection are disposing off used needles incinerating anything that came into contact with the patients secretions like beddings guaze IV lines clothes etc


  3. And quarantine people who came into contact with an Ebola patient like family members and test them too
    Supportive measures include maintaining hemodynamic status with IV fluids and pharmacological cardiac support


  4. Hope all of you found the post to be informative and helpful! Thanks for the comments.

    The correct answer is B. Genetic Drift. Genetic drift occurs with a random mutation in the viral genome; in this case a point mutation was discovered in the RNA genome. Genetic drift can cause epidemics, whereas genetic shift can cause pandemics.

    A is incorrect. Genetic shift is seen when segmented genomes undergo reassortment (usually seen in the orthomyxoviruses and rotaviruses). A pandemic is more likely to occur if a new strain has dramatically altered viral surface glycoproteins (such as hemagglutinin in the influenza virus). First Aid 2014 has a helpful mnemonic device to remember this association. Sudden Shift is more deadly than graDual Drift.

    C is incorrect. Reassortment is incorrect because it is the mechanism used by segmented viruses to undergo “high-frequency recombination”. Reassortment leads to genetic shift.

    D is incorrect. Phenotypic mixing is a mechanism used by two different viruses to infect a cell. The first virus may be unable to infect the cell alone without the help of a second virus, which has the necessary surface proteins to allow for infection. Important to note that NO genetic exchange occurs between the two viral genomes, meaning the progeny of the first virus will have the original surface proteins that cannot infect cells without the assistance of the second virus.

    E is incorrect. Specialized transduction is the use of a lysogenic phage to incorporate viral DNA into bacterial chromosome. Therefore, it is related to bacterial genetics, not viral genetics.


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