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HCV, HIV

Alison Evans aevans at castor.fccc.edu
Wed Jan 18 13:53:25 EST 1995


 
> Would there be any epidemiologists out there who could pitch in?
>
     Epidemiologist to the rescue here.  I have been watching this thread with
trepidation, but it is well known that epidemiologists rush in where angels
fear to tread, so here goes.
     First of all, Audra is *absolutely* incorrect that HIV prevalences in
people "her age" are as high as 10-25%.  You would find prevalences in that
order only among the very highest risk groups in the world, e.g. very sexually
active gay men in large cities of the US, or sexually active adults of both
sexes in some areas of Central Africa.  
     Bret is probably correct that HIV gets more press because of its
demographics, but I think it is also because it is a novel disease and such a
devastating one.  Though the HCV virus has only recently been discovered, its
existence was known for many years before that and certainly other forms of
viral hepatitis were also well known.  The jury is still out on exactly how
lethal HCV infection can be.  The estimate of 50% chronic infections is
disputed by some, and the number of chronic infections that result in serious
liver disease and/or hepatocellular carcinoma is also not known for sure.
There appear to be significant differences in pathogenicity between different
strains of HCV.  It is generally accepted, however, that HCV infection results
in chronic infection much  more frequently than does hepatitis B infection, for
instance.
     Bret is also correct that HCV tends to be a disease of older people than
HIV.  This is probably because -- largely because of HBV and HIV -- our methods
for screening blood donors are so much better now than they were 20 years ago.
IN the 1960's, your chances of getting hepatitis (B or C) from a  single blood
transfusion were as high as 35%.  Older people alive today may have received
transfusions then and still be seropositive for the antibodies.  Few people
have gotten HCV from blood transfusions since the early 1980s, but there is an
increasing amount of it among younger people because of IV drug use.  HCV has
also been around a lot longer in the US population that has HIV.  And people
with HIV infection die off a lot faster than people with HCV infection.
     I would also caution against the use of the CDC figures posted by WC
Wilson to compare incidence of HIV infection to HCV infection.  Although Non-A,
non-B hepatitis is a reportable disease, it is vastly under-reported.  In
addition, reporting usually picks up only acute cases. Most HCV infections may
not produce symptoms at the time of initial infection, and these asymptomatic
infections are the ones most likely to go on to become chronic.  These numbers
never get reported to the CDC.  Indeed, most people with chronic infection
probably never know about it.  What we see in the clinical literature are
reports about very serious outcomes of chronic HCV infection -- cirrhosis,
chronic active hepatitis, liver cancer.  But there is really no good source of
information as to what percentage of people initially infected encounter these
outcomes.





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