Ebola is in the family Filoviridae
(family in regards to taxonomy, which helps distinguish species). There are two
types of filoviruses: the Marburg virus and the Ebola virus. Within the Ebola
virus, there are 5 known strains, each named after the place it emerged: Tai
Forest (formerly known as Ivory Coast), Sudan, Zaire, Reston, and Bundibugyo.
The only known filovirus that does not cause hemorrhagic fever in humans is the
Ebola-Reston strain, which can still be fatal to monkeys.
Filoviruses may appear in several
shapes which means they are pleomorphic. Some are long, sometimes branched
filaments. Others are shorter and can be shaped like a “6,” a “U,” or a circle.
They may measure up to 14,000 nanometers in length with a uniform diameter of
80 nanometers. They all are enveloped in a lipid (fatty) membrane and contain
single-stranded, negative sense RNA (ribonucleic acid).
The RNA is where the virus stores
all its genetic information. This is where any virus can get a little hard to
deal with. In humans and most other living things, DNA (deoxyribonucleic acid) stores
all the genetic code and RNA is used to help make proteins for the cell. When
DNA replicates (copies itself before the cell divides), there are a number of
polymers double checking on the newly made DNA to be sure the copy is correct.
RNA doesn’t have an
error-correction polymerase. This means it cannot be sure what’s copied is the same.
As mistakes accumulate, the virus evolves further and further from the original
virus. But Ebola isn’t just RNA. It’s negative-stranded RNA. To replicate,
negative strands must first make a positive opposite copy and then make the end
product. Neither of these processes has any polymers to correct errors. The
possibility for error has now doubled.
The speed of evolution also depends
on how quickly it is transmitted between victims. A Broad Institute/Harvard
University has reported there is a two-fold increase in the number of changes
in genome sequences compared to previous outbreaks. This is probably due to the
many transmissions from person-to-person. Hopefully, the data that is being
analyzed will help us understand how to better manage any future outbreaks.
Sources:http://theconversation.com/genetic-evolution-how-the-ebola-virus-changes-and-adapts-31525
http://pathmicro.med.sc.edu/mhunt/rna-ho.htm
https://web.stanford.edu/group/virus/filo/history.html
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