envrionment, immune system & viruses

[asmjz at orion.alaska.edu]

	Just a quick question regarding environment and the immune system.
If I recall correctly no one infected in the U.S. with the ebola virus has
died ( i.e. I remember reading a few articals, I think in Lancet, about CDC
workers infected with ebola and it was not the Reston strain).  But, ebola
outbreaks in Zaire (1976) had high mortality rates.  Were the environmental
conditions (i.e. health care, sanitation, etc.) in Zaire conducive to poor
or compromised immune systems, and perhaps the environmental conditions
coupled with the ebola virus led to the high mortality rate in Zaire 1976???
Also, were any other pathological agents found in blood and tissue samples
during the Zaire ebola outbreak????
Note:  In regards to U.S. infections I'm NOT talking about ebola Reston 
infections.
Note: I've read (I forget the journal maybe Virology?) that people indigenous 
to the African rain forests have tested positve for antibodies against the
ebola virus.  Does anyone know of studies on viral outbreaks in populations
of people indigenous to African rain forests.  If the idigenous people of
the rain forest do contract ebola why does it not have a high mortality rate?
Environmental conditions??
cheers
Michael