Ebola—A Hemorrhagic Fever of West Africa

The whole world is worried these days about the possible spread of a West African disease, Ebola fever. That fear is justified; many of the victims of the disease have died—about 50% of them in Sierra Leone and Liberia, at last count.

The disease is communicable from person to person. It is transmitted by touching, coughing, and eating contaminated foods. There is no specific treatment—only good nursing care. Careful means of avoiding direct contact with patients can prevent person-to-person contact and spread of the infection.

So far, in the present spread of Ebola in West Africa, three doctors working in the infection have contracted the disease.

The disease is one of 12 known hemorrhagic diseases. In West Africa, the ones that cause problems are yellow fever, Marburg fever, Ebola fever, and Lassa fever.

Ebola fever has five strains of the virus that is causing the problem. The one from Liberia and Sierra Leone is the most deadly of the five.

It is significant in looking at disease epidemics to realize several things: In the early stages when a society is dealing with a relatively new disease, the disease appears to have a much higher mortality rate than it subsequently proves to have. (Ebola is not exactly a new disease; it has been known since 1976 when it was first described in Sudan and Zaire. However, it has not been a large threat until very recently.) This is because only the most severe cases come to the attention of the public and the medical community initially—many of the new infections cause death; but later, the disease is discovered in patients who are only mildly ill or who might not even have any symptoms (They are carriers of the infection.)

 The other reason for the declining mortality from a new disease is that the virus evolves into a less dangerous infectious agent. From the disease agent’s (the virus’s) point of view, it is not advantageous for that virus or infectious agent to kill its victims. It is better from the point of view of the virus to infect victims and have them live to spread the infection to other people.  So…as a result of this evolution, less dangerous forms of the virus survive while the more deadly forms die out, themselves.

The last point to remember in the understanding of epidemics is that they have all mostly ended for no known reason. This has happened repeatedly in the history of the world’s epidemics, e.g., plague of the 15^th Century. No effective cure for that disease was known then; but the disease quit causing epidemics, anyway; nobody knows why.