The Ebola Virus Investigating a Killer





The female scientist, fully dressed in a quarantine outfit, anxiously prepared to inject a sedative into the arm of the delirious patient. Although he was being held down by several pairs of arms, he was still putting up a good fight. The needle goes in. He jerks. The needle flicks into the forefinger of the scientist. The scientist stares at her finger in shock and disbelief, and runs away. It would only be a few days now before she would die.
Thankfully, this is only a scene out of the 1995 box-office hit, Outbreak (Fig. 3), which was about Americans fighting against the spread of a nationwide epidemic caused by one of the most feared viruses of our time: the Ebola virus. I chose this topic out of curiosity; everyone shudders at the mention of this virus, and I have always wondered why people do so. This project will give me the opportunity to further investigate what are the factors which make the Ebola virus so deadly and so feared by man.
What exactly is Ebola? Ebola is a viral hemorrhagic fever actually named after the River Ebola in Zaire, Africa, where it was first discovered. It belongs to a genus of ribonucleic viruses called filoviruses, under the family Filofiridae, which are characterized by their filament-like (thread-like) appearance with a little hook or loop at the end. Only five viruses exist in this family: the not-as-deadly Marburg, and the four Ebola strains: Ebola Zaire, Ebola Sudan, Ebola Tai and Ebola Reston. The latter only affects monkeys and hence is not harmful to man. (Ebola-Reston-infected monkeys display symptoms similar to the symptoms of the Ebola- Zaire virus shown in humans.)
The first emergence of Ebola into the modern world took place in 1976, its ‘grand entrance’ in the form of two major outbreaks which happened almost simultaneously in Zaire (Fig. 2) and western Sudan, Africa. The mortality rate was 88% in Zaire and 53% in Sudan. More than 550 cases were reported and more than 340 died. The third outbreak took place in Sudan in the same area as before, resulting in 34 cases and 22 deaths. More recently, outbreaks have occurred in Kikwit, Zaire in 1994, and Gabon in 1994 and 1996. The most recent outbreak may have possibly taken place in Congo in early 1999; a virus similar to Ebola killed 63 people. There has only been one recorded case of Ebola Tai infection: in 1994, a Swiss researcher caught the virus after conducting an autopsy on a chimpanzee in the Tai Forest, Ivory Coast. She was given intensive treatment in Switzerland, and survived. In total, there have been 1100 cases and 793 deaths officially resulting in Ebola since its discovery. (Tables I and II)
The viruses in this family range from 800 to 1000 nanometers in length. Marburg and Ebola are distinguished by their length after purification. Infectivity depends on particular lengths: the longer, the more infectious. All Ebola viruses measure up to about the same length. Each virus particle consists of a helical-coiled tube made of four virally encoded proteins. This strand of RNA is found in an envelope formed from the host’s plasma cell membrane, which is now spiked with another carbohydrate-coated viral protein. Differences in gene sequence and very small differences in serological nature are what make each Ebola virus unique from each other, with its own antigenic and biological properties.
The time needed for Ebola virus replication in infected body cells takes less than eight hours. Hundreds to thousands of new viral particles can be produced and released from the host cell within days or even hours before the host cell dies. This replication process is repeated several times in an Ebola patient before symptoms begin to show.
The diagnosis of Ebola is made by the detection of Ebola antibodies, antigens or genetic material, or by the culture of the virus, in blood or other bodily fluid specimens that are examined in specialized laboratory tests. Such tests present a very extreme biohazard, so they are conducted in special high-containment laboratories to ensure maximum protection for scientists. The Center of Disease Control and Prevention (CDC) has classified the Ebola virus under Biosafety Level 4, which requires the greatest safety precautions. The technique used to diagnose the virus