virulence

ctfaulkn at utkvx.utk.edu ctfaulkn at utkvx.utk.edu
Thu Dec 22 02:16:35 EST 1994


In Article <199412211632.IAA19819 at net.bio.net>
CGE at CU.NIH.GOV writes:
>
>I am not sure how you are differentiating pathogenicity and virulence
>here. 

Relative pathogenicity is defined as:

	number of clinical cases resulting from infection
-----------------------------------------------------------------
     total number of infections in the population under investigation

Relative virulence is defined as:

	number of clinical cases w/serious manifestations (mortality)
----------------------------------------------------------------------
    total number of clinical cases resulting from infection
		

>Trichomonas gallinae is a pathogen that is normally avirulent, but is
>virulent in abnormal hosts.

I would say T.gallinae is an infectious agent with pathogenic potential in
abnormal hosts and locations within hosts.  Not all infections result in
disease, and variation in the virulence of isolates accounts for excess
morbidity and mortality in the population of clinical cases.

>
>It seems that the major difference we have is over pathogenicity being
>an either/or category. 

	[snip, snip]

>To me, pathogenicity is an absolute category while virulence is a
>relative category. 

I don't guess i'm philosophically invested in either view, i'm only interested
in using the terms for which the most consensus exists. Is the difference in
definitions a discipinlary one?  I've given the citation for one epidemiology
textbook definition, is there one for parasitology? 

Merry Christmas!!!!

CTF





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