How the Ebola Virus Kills People
© Neal Rolfe Chamberlain
The Ebola virus causes a disease called hemorrhagic fever. It is a very deadly virus killing 50 to 90 percent of those who are infected with it. Several outbreaks of hemorrhagic fever have occurred in the last two years in Africa. A couple of books have been written on this very lethal infection (e.g., The Hot Zone).
This virus causes death by making the patient's capillaries (the very small blood vessels that carry our blood to the cells of our body) leak blood. A person with hemorrhagic fever literally leaks blood from their blood vessels. When you lose blood it is called an hemorrhage, hence the name hemorrhagic fever.
Initially people with hemorrhagic fever have flu-like symptoms (fever, tiredness, loss of appetite) that rapidly progress to the person bleeding out of their nose, mouth, tear ducts, ears, rectum, and in their stomach. So much blood is lost that the person's blood pressure goes down and eventually they go into shock (the brain doesn't get enough oxygen and the patient faints, their skin feels clammy, etc.) and in many cases die.
A recent article in the Feb. 13, 1998, issue of Science contains the results of some fantastic research from Dr. Gary J. Nabel's laboratory. They have been able to identify the viral glycoprotein that helps the virus bind to human cells and what human cells the virus binds to in the body. They have also found that a different form of this glycoprotein can slow down our bodies immune response to this viral infection.
A glycoprotein is basically a protein with some sugars added to it. Glycoproteins have been very useful in helping viruses bind to cells. The AIDS virus uses a glycoprotein (gp120) to bind to our cells as well. The Ebola virus uses a glycoprotein to bind to endothelial cells. Endothelial cells are the cells that form a lining in our blood vessels and prevent the blood vessels from leaking blood all over the place. After the Ebola virus attacks and kills the endothelial cells a leak can result in the blood vessels. Now we know how Ebola virus can cause such dramatic blood loss in people with hemorrhagic fever.
The other glycoprotein slows down our immune system by stopping neutrophils from becoming activated. Neutrophils are white blood cells that are first on the scene of a viral invasion. When activated they can help to eliminate the cells that are infected with Ebola virus. However, if these cells are
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