Hi Brian,
I think Tony was referring to the Tai strain of Ebola. The 1970s and 1995
strains of Zaire Ebola are quite similar, but the Tai strain is somewhat
divergent.
This is probably not surprising since the selective pressures in the Tai
Forest may be quite different than those in Zaire.
Cheers,
Cliff
At 11:30 AM 1/31/96 -0700, you wrote:
>> "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
>Diseases.
>>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.
>>Brian
>>Clifford W. Bond
Department of Microbiology
Montana State University
Bozeman, MT 59717-0352
Telephone - 406 994-4130
Telefax - 406 994-4926
Internet - umbcb at gemini.oscs.montana.edu
