🚀 go-pugleaf

In article <01bce6c5$426089a0$LocalHost@dialup.ozemail.com.au>,
Rex <dmayo@ozemail.com.au> wrote:
>Ebola Zaire is a naturally occurring viral agent. That has to count for
>something
>
>Rex
>
>Philip Ross <pross@inhb.co.nz> wrote in article
><877341053.9279@dejanews.com>...
>> Kym Horsell has suggested that plutonium is far more toxic than common
>> highly toxic substances 
>
><very large snip>
> 
>> My vote for most toxic substance known to man goes to the Ebola Zaire
>> virus. As little as 5 viral particles; that's just 35 molecules, can
>cause
>> an explosive infection which has a case fatality rate in excess of ninety
>> percent. 
>>Furthermore, it amplifies itself billions of times in the course
>> of the infection and its origins and natural hosts are unknown.

Of course, this part has been amplified by various media. There are
some studies that give large fataly rates for various Ebola/Marburg strains,
I'm not sure that Zaire (specifically) was subject to such investigation.

The US Amry Medial Research Inst did some studies in
1996 in which monkeys were exposed to aerosols containing
Ebola Zaire. Some of the experiuemental animals were
exposed to as FEW as 400 plaque units. All (I don't
know how many) developed Ebola-related pneumonia within 
several days. Another study from USAMRID published in Feb 
of that year reported 2 of 8 (i.e. 25%) experiemntal 
animals developed "severe respitory infection" from Ebola 
aerosols.

There is then quite some question as to how virulent (generic) Ebola is.
Some strains -- fortunately for e.g. DC -- seem pretty restricted to 
non-humans. And, as you mention, some studies only concerned "case fatality"
rates -- it's pretty clear the risk of developing any symptoms given initial
exposure to the hypothetical (and somewhat out-of-context in the same
statement) "5 particles". Since the diease is not presently involving
millions of obvious casualties in C Africa, Germany or the US, we can 
hypothesise exposure-to-development has a fairly low probability.

Ergo, Ebola is one of those things that are arguably dangerous,
but have small risks associated with them -- given the present
circumstances. And that's one of the features with "risk assessment";
circumstances can change quite quickly. "Dangerousness" is a fairly
fixed for a given agent.

Finally, "35 molecules" doesn't mean terrificly much -- except as
a media "factoid" -- when we're talking proteins.

---
See (perhaps in order):

Jaax, Davis & Geisbert et al,
"Lethal experimental infection of rhesus monkeys
with Ebola-Zaire (Mayinga) virus by the oral
and conjunctival [i.e. eye] route of exposure",
Archives of Pathology and Laboritory Medicine
V 120, Feb 1996, pp 140--155.

Jaax, Jarhling & Geisbert et al,
"Transmission of Ebola (Zaire) to uninfected control
monkeys in a biocontainment laboritory", Lancet Vol 346,
Dec 1995, pp 1669--71.

Johnson, Jaax, White and Jahrling,
"Lethal experimental infections of rhesus monkeys by
aerosolized Ebola virus", Int J of Exp Pathology,
Vol 76 1995, pp 227--36.