In article <MAILQUEUE-101.950301095318.416 at molbiol.uct.ac.za>, ED at molbiol.uct.ac
.za ("RYBICKI, ED") writes:
>> To: virology at net.bio.net>> From: fmzerbini at UCDAVIS.EDU (Francisco Muril Zerbini)
>> Subject: Re: ebola info
>>> On 28 Feb 1995, Mathew Roberts wrote:
>>>> > I'm a senior Microbiology student at Colo. State Univ. I've
>read "The > > Hot Zone," and was wondering how much is known about
>Ebola, and if there
>>> I have a suggestion to make. There have been so many messages on
>Ebola > lately, could someone with more knowledge on this subject
>(and time to > spare) make a mini-FAQ on Ebola and related viruses ?
>>Herewith a contribution. Excerpted from ebola.html at
>http://www.bocklabs.wisc.edu/ed/, and
>http://www.uct.ac.za/microbiology/ebola.html>>EBOLA VIRUS
>>Ebola virus, a member of the Filoviridae, burst from obscurity with
>spectacular outbreaks of severe, haemorrhagic fever. It was first
>associated with an outbreak of 318 cases and a case-fatality rate of
>90% in Zaire and caused 150 deaths among 250 cases in Sudan. Smaller
>outbreaks continue to appear periodically, particularly in East,
>Central and southern Africa. In 1989, a haemorrhagic disease was
>recognized among cynomolgus macaques imported into the United States
>from the Philippines. Strains of Ebola virus were isolated from
>these monkeys.
>>Serologic studies in the Philippines and elsewhere in Southeast Asia
>indicated that Ebola virus is a prevalent cause of infection among
>macaques (Manson 1989).
>>These threadlike polymorphic viruses are highly variable in length
>apparently owing to concatemerization. However, the average length
>of an infectious virion appears to be 920 nm. The virions are 80 nm
>in diameter with a helical nucleocapsid, a membrane made of 10 nm
>projections, and host cell membrane. They contain a unique
>single-stranded molecule of noninfectious (negative sense ) RNA. The
>virus is composed of 7 polypeptides, a nucleoprotein, a
>glycoprotein, a polymerase and 4 other undesignated proteins.
>Proteins are produced from polyadenylated monocistronic mRNA species
>transcribed from virus RNA. The replication in and destruction of
>the host cell is rapid and produces a large number of viruses
>budding from the cell membrane.
>>Epidemics have resulted from person to person transmission,
>nosocomial spread or laboratory infections. The mode of primary
>infection and the natural ecology of these viruses are unknown.
>Association with bats has been implicated directly in at least 2
>episodes when individuals entered the same bat-filled cave in
>Eastern Kenya. Ebola infections in Sudan in 1976 and 1979
>occurred in workers of a cotton factory containing thousands of bats
>in the roof. However, in all instances, study of antibody in bats
>failed to detect evidence of infection, and no virus was
>isolated form bat tissue.
>>The index case in 1976 was never identified, but this large outbreak
>resulted in 280 deaths of 318 infections. The outbreak was primarily
>the result of person to person spread and transmission by
>contaminated needles in outpatient and inpatient departments of a
>hospital and subsequent person to person spread in surrounding
>villages. In serosurveys in Zaire, antibody prevalence to Ebola
>virus has been 3 to 7%. The incubation period for needle-
>transmitted Ebola virus is 5 to 7 days and that for person to person
>transmitted disease is 6 to 12 days.
>>The virus spreads through the blood and is replicated in many
>organs. The histopathologic change is focal necrosis in these
>organs, including the liver, lymphatic organs, kidneys, ovaries
>and testes. The central lesions appear to be those affecting the
>vascular endothelium and the platelets. The resulting manifestations
>are bleeding, especially in the mucosa, abdomen, pericardium and
>vagina. Capillary leakage appears to lead to loss of intravascular
>volume, bleeding, shock and the acute respiratory disorder seen in
>fatal cases. Patients die of intractable shock. Those with severe
>illness often have sustained high fevers and are delirious,
>combative and difficult to control.
>>TREATMENT OF EBOLA
>>No specific antiviral therapy presently exists against Ebola virus,
>nor does interferon have any effect. Past recommendations for
>isolation of the patient in a plastic isolator have given way to
>the more moderate recommendation of strict barrier isolation with
>body fluid precautions. This presents no excess risk to the hospital
>personnel and allows substantially better patient care. The major
>factor in nosocomial transmission is the combination of the
>unawareness of the possibility of the disease by a worker who is
>also inattentive to the requirements of effective barrier nursing.
>after diagnosis, the risk of nosocomial transmission is
>small.
>>PREVENTION AND CONTROL OF EBOLA
>>The basic method of prevention and control is the interruption of
>person to person spread of the virus. However, in rural areas, this
>may be difficult because families are often reluctant to
>admit members to the hospital because of limited resources and the
>culturally unacceptable separation of sick or dying patients from
>the care of their family. Experience with humandisease and primate
>infection suggests that a vaccine inducing a strong cell- mediated
>response will be necessary for virus clearance and adequate
>protection. Neutralizing antibodies are not observed in convalescent
>patients nor do they occur in primates inoculated with killed
>vaccine. A vaccine expressing the glycoprotein in vaccinia is being
>prepared for laboratory evaluation.
>>Alison Jacobson, 1994
>>>>> _____________________________________________________
> | Ed Rybicki, PhD | (ed at molbiol.uct.ac.za) |
> | Dept Microbiology | University of Cape Town |
> | Private Bag, Rondebosch | 7700, South Africa |
> | fax: xx27-21-650 4023 | tel: xx27-21-650 3265 |
> | URL: http://www.uct.ac.za/microbiology |
> -----------------------------------------------------
>
