HIV-1 Adaptation to host/various musings

A.J.Cann nna at le.ac.uk
Mon Oct 23 07:46:07 EST 1995


york at mbcrr.dfci.harvard.edu (Ian A. York) wrote:
>I mean neither 99.9% nor 100%.  Last time I checked on this, I think I 
>found 5 examples of people surviving rabies following onset of clinical 
>signs.  Since I also found (last easy-to-find number was 1985) that at 
>least 20,000 people per year die of rabies, I think my 99.99999% is 
>pretty accurate - certainly more accurate than 99.9%.  Moreover, I think 
>I recall seeing in ProMed that the 5th known survivor is now suspected to 
>have been infected by a related lyssavirus, rather than rabies itself.  
>Do you have a reference for your 99.9%?

Not to hand, but "at least 20,000" is hardly a reliable figure with which 
to try to perform calculation accurate to 6 decimal places! C'mon, let's 
not split hairs. 5 survivors is almost certainly a gross underestimate & 
it's more complicated than that - the chances of survival when bitten on 
the hands or feet are greater than if bitten on the face or neck.

>>host of rabies virus - they are dead end hosts who do not play a 
>>significant part in the transmission of the virus over "thousands of 
>>years". Hence each human infection is essentially a new event & the virus 
>>does not have chance to "adapt to it's host" in evolutionary terms.
>
>Can you name *any* species which survivies rabies infection?  The 
>prevalent belief that bats can have persistent infection (again this is 
>as of the last time I checked) seems to be wrong; they simply don't die 
>quite as fast as other species.

Well, in the sense that they survive long enough (years in some cases) to 
transmit the virus to other hosts of the same species, yes, e.g. foxes, the 
natural hosts for sylvan rabies.

Dr Alan J. Cann  PhD,   Department of Microbiology & Immunology,
University of Leicester,  P.O. Box 138,  Medical Sciences Building,
University Road, Leicester LE1 9HN,  UK.
Email: nna at le.ac.uk     http://www-micro.msb.le.ac.uk/AJC/nna.html





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