Viral virulence

[Patrick O'Neil]

On 14 May 1995 stuhansenmic at SPOCK.COLSF.EDU wrote:

> 
> I'm an undergrad bio major who has been lurking here for some time.  With
> all this talk of Ebola, it seems to me that a virus that destroys its host
> very quickly is certainly not helping itself.  Would'nt it more beneficial
[...]

It depends on the mode of transfer, first of all, but in general terms 
this is correct.  The thing is, Ebola is not normally a human (nor 
monkey) virus so it is not particularly adept at highly successful 
transfer.  This would change somewhat if it became easily aerosolized but 
it is likely that the natural host is not affected in the same way nor 
with the same rapidity as are humans and monkeys.  Insect-borne viruses 
and bacteria that really lay out humans (or horses, or whatever) do not 
do anything to their insect vectors - they sit rather quiescent within 
their cells (not in their stomachs) and are then injected into 
unfortunate animals.  What do the equine encephalitis viruses "care" if 
they lay up and kill their horse hosts (or human) as long as the victim 
is subject to further insect biting.  No matter how ill the victim gets, 
the mosquito will drink blood, perhaps more easily from a sick and 
debilitatied host, and pass it on with ease.  For this reason, many 
insect-borne diseases are capable of being particularly nasty no matter 
how long they've been around.  
  An aerosolizable pathogen can get real deadly so long as population
density is high and the victim isn't laid up too soom after infection. 
Then, so long as the victim has lots of contact with other potential
hosts, and sneezes and coughs in their presence, then the pathogen can get
around just fine.  For Ebola to really be an effective pathogen in humans
on a wide scale, it would either need to be insect transferable or it
would have to become a little slower to lay up its human host and become 
aerosolizable, thus allowing wider application to potential hosts...THEN 
it can kill you.

Patrick