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Ebola followup NEW!

bhjelle at unm.edu bhjelle at unm.edu
Wed Jan 31 13:30:49 EST 1996

> "Comparing the new strain's RNA sequence with those from earlier outbreaks
> reveals wide diversity, notes Anthony Sanchez, a research officer in the
> Special Pathogens Branch at the U.S. Centers for Disease Control and
> Prevention (CDC) in Atlanta. That's not surprising, he notes, because
> Ebola, like other RNA viruses, has an error-prone replication process,
> which would boost the frequenzy of mutations and thus the emergence of new
> strains. Sanchez says that the high mutation rate increases the chance
> that the disease could someday adapt a more contagious form."
> SCIENCE, Vol. 268, 19 May 1995, p. 974
This is a remarkable quote, because it seems to be
quite at odds with data that is being presented
at meetings, and published in Emerging Infectious

Assuming that Tony is referring to the 1995 Kikwit, Zaire
virus, it has been repeatedly noted that the Kikwit virus is very
nearly identical to the virus isolated during the mid-
1970s Zaire outbreak. While comparison of isolates from
Zaire, Sudan, and Cote d'Ivoire show large differences,
these could reflect adaptation of the viruses to as yet-
unidentified host animals. Such adaptation could result
in profound differences among isolates even if each virus
is itself exquisitely stable. The sequences from Kikwit
certainly would argue that Ebola is stable
over time, and even over rather large geographic spaces.

The mutability of RNA viral genomes has been discussed
here many times before, but continues to be misconstrued
by people, either out of misunderstanding or for some
other reason. Suffice it to say that an error-prone
replicase does *not* necessarily result in a naturally
unstable virus. I think this misconception about the
inherent instability of RNA genomes in nature is yet
another legacy of the popular assumption that all viruses are
like the AIDS virus.



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