Tuesday, December 26, 1995 23:32:26
               Factoids Item
       From:           Sylvia Feder,Medic One OnLine
       Subject:        Ebola virus FAQs
       To:             Factoids
                       
       Cc:             
From Pat Plummer, MD, and the OneNet via dBUG
> 
> Frequently Asked Questions and Answers
> 
>    What exactly is Ebola?
> 
> Ebola (ee-BOH-luh) is a virus named after a river in Zaire, its first
> site of discovery. A usually fatal filovirus which affects monkeys and
> humans, it is a cause of viral hemorrhagic fever -- there are others.
> Filoviruses are string-shaped, often with a little hook or loop at one
> end. Another, somewhat less deadly filovirus is the Marburg virus.
> 
>    What varieties are known to exist?
> 
> Ebola Sudan (EBOS), Ebola Zaire (EBOZ), and Ebola Reston (EBOR).
> 
> It is somewhat unclear to researchers to what extent EBOS, EBOZ and
> EBOR are really three different viruses (9).
> 
> Newsflash: It has just been announced that a fourth strain of Ebola,
> also affecting humans, has been identified: it was isolated from a
> blood sample taken from a Swiss zoologist who contracted it in Ivory
> Coast, West Africa last fall from an infected chimpanzee.
> [Fortunately, she survived, thanks to intensive medical care.] The
> announcement was made in the 20/5/95 issue of the Lancet. Ref.: V.O.A.
> 
>    How do these varieties differ?
> 
> Clinically, they all produce similar effects. Ebola Sudan and Ebola
> Zaire affect humans as well as monkeys; Ebola Reston harms monkeys,
> but not humans. (The Ebola Reston incident is the main subject of
> Richard Preston's book The Hot Zone.) We are all very lucky that
> humans seem to be asymptomatic in response to Reston, since there were
> indications at the time of the incident that it was airborne, unlike
> (apparently) the other two.
> 
>    How long is the incubation period/onset of symptoms?
> 
> Anywhere from 4 to 21 days.
> 
>    What are the symptoms?
> 
> Quoting the CDC:
> 
>      All forms of viral hemorrhagic fever begin with fever and
>      muscle aches. Depending on the particular virus, the disease
>      can progress until the patient becomes very ill with
>      respiratory problems, severe bleeding, kidney problems, and
>      shock. The severity of viral hemorrhagic fever can range
>      from a relatively mild illness to death.
> 
> EBOZ seems to be fatal in about 90% of the cases. EBOS is fatal in
> about 60%. EBOR is not fatal to humans.
> 
>    Is there any cure or vaccine?
> 
> No.
> 
>    How does it damage (and usually kill) its victims?
> 
> By slowly dissolving their organs, blood cells and connective tissue,
> causing massive and usually fatal internal hemorrhaging.
> 
>    How is it transmitted?
> 
> Ebola virus is spread through close personal contact with a person who
> is very ill with the disease. In previous outbreaks, person-to-person
> spread frequently occurred among hospital care workers or family
> members who were caring for an ill person infected with Ebola virus.
> Transmission of the virus has also occurred as a result of hypodermic
> needles being reused in the treatment of patients. Reusing needles is
> a common practice in developing countries, such as Zaire and Sudan,
> where the health care system is underfinanced. Medical facilities in
> the United States do not reuse needles.
> 
> Ebola virus can also be spread from person to person through sexual
> contact. Close personal contact with persons who are infected but show
> no signs of active disease is very unlikely to result in infection.
> Patients who have recovered from an illness caused by Ebola virus do
> not pose a serious risk for spreading the infection. However, the
> virus may be present in the genital secretions of such persons for a
> brief period after their recovery, and therefore it is possible they
> can spread the virus through sexual contact.
> 
> Ref: CDC
> 
>    Is Ebola airborne?
> 
> The Zaire and Sudan strains are not airborne. The Reston strain
> appears to have been transmittable by airborne means, but that strain
> is not harmful to humans.
> 
>    Geographically, where does Ebola come from?
> 
> The Sudan and Zaire strains may come from the rainforests of
> northeastern Zaire and/or somewhere nearby in the bordering nations of
> Sudan, Uganda, and Kenya. The Marburg filovirus was circumstantially
> linked to the Mt. Elgon region near the Kenya-Uganda border. The
> Reston variety occured in monkeys imported from the Philipines, so
> there may be reservoirs in Asia as well. Preston speculates that an
> Ebola strain may have been introduced into the Phillipines from Africa
> by the rumored illegal importing of African game animals to remote
> areas of the Philipines by rich Filipino "sportsmen".
> 
>    What is the natural reservoir for Ebola?
> 
> Attempts to find the source of the Ebola virus have been unsuccessful
> despite collection and analysis of ecologic samples from bats,
> monkeys, spiders and ticks. This question is currently the subject of
> ongoing speculation. See, for example, discussions going on in the
> bionet.virology USENET news group.
> 
>    What is the probability of Ebola mutating and becoming airborne?
> 
> RNA viruses are known to undergo rapid genetic changes (1). The Ebola
> virus is subject to some (but not all) of these mutation processes. To
> become "airborne", the Ebola genome (RNA) would have to mutate in such
> a way that its outer protective coating of proteins (capsid) could
> resist the forces to which they are subjected in air (e.g., dryness).
> There are no exact measures of the rate of mutation in Ebola, but the
> probability of the required mutation(s) happening is very low.
> 
>    What has caused Ebola epidemics to end in past occurrences?
> 
> Previous outbreaks of Ebola appear to have continued only as long as a
> steady supply of victims came in contact with body fluids from the
> infected. The epidemics were resolved by teaching the local population
> about how to avoid spreading the disease and improving conditions at
> hospitals in impacted areas (unsterilized needles and syringes were a
> major factor in the 1976 outbreak in Zaire). Ebola's virulence may
> also serve to limit its spread: it's victims die so quickly that they
> don't have a chance to spread infection very far.
> 
>    Can blood from survivors be used to make a serum?
> 
> No. Normally, one can mix serum from a patient recovering from an
> infection with a test tube containing the involved virus and then
> inject a test animal with the mixture and expect that the convalescent
> serum 'killed' the virus. This is not the case with Ebola (7). This
> also means that the serum is ineffective in treating someone else who
> is infected.
>     ------------------------------------------------------------------------
> 
> 
> Notes
> 
>   1. The three most common mechanisms are: (a) nucleotide
>      substitutions resulting from purportedly high error rates during
>      RNA synthesis (2,3); (b) reassortment of the RNA segments of
>      multipartite genomic viruses (4,5); (c) RNA-RNA recombination
>      between non-segmented RNAs. Ebola virus can use only the first
>      and the third mechanisms as it has only one segment of RNA by
>      capsid.
>   2. Holland, J. et al. 1982 Rapid evolution of RNA genomes. Science
>      215: 1577-1585.
>   3. Steinhauer, D.A. and J. Holland. 1986. Direct method for
>      quantitation of extreme polymerase error frequencies at selected
>      single base sites in viral RNA. J. Virol. 57: 219-228.
>   4. Fields, B.N. 1981. Genetics of Reovirus. Curr. Top. Microbiol.
>      Immunol. 91: 1-24.
>   5. Palese, P. 1977. The genes of Influenza virus. Cell 10: 1-10.
>   6. Lai, M.M.C. 1992. RNA recombination in animal and plant viruses.
>      Microb. Rev. 56: 61-79.
>   7. Many infections create an immune response that includes
>      antibodies that will bind to and inactivate the virus when
>      exposed in vitro. The antibodies raised by people or animals
>      after Ebola infection apparently lack the ability to neutralize
>      viruses experimentally (8).
>   8. Peters, C.J. et al (1993). Filoviruses (p. 161) in Emerging
>      Viruses, edited by Stephen S. Morse. Oxford Univ. Press.
>   9. Peters, C.J. et al (1993). Filoviruses (p. 163) in Emerging
>      Viruses, edited by Stephen S. Morse. Oxford Univ. Press.
> 
>     ------------------------------------------------------------------------
> 
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