Lynton:
> I know little or nothing about HIV, but the information in Lucia's post does
> not seem to rule out a possibility that what is being called a virus (HIV)
> could be "x": a new type of infectious agent (if you call bacteria and virii
> (?) agents).  And it _could_ be that "x" could cause AIDS in people whose
> immune systems are compromised, or that can't deal with the infection due to
> heredity.
>
> AIDS, being "Acquired Immuno Deficiency Syndrome", suggests that "x"/HIV is
> responsible for degrading the immune system.  But there are stories of
> people who are diagnosed positive for "x"/HIV who are then later are found
> to be negative.  Suggestions are that (A) the body has dealt with the
> infection successfully, (B) that "x"/HIV has gone "underground" with the
> suggestion that it could surface again spontaineously.

Carol:
Those suggestions would be good possibilities if the test in question
were one that could detect HIV directly, but the tests used for HIV do
not test for HIV directly.  They test for antibodies.  That makes all
the difference in the world.  In both cases, A & B above, such a test
should still come out positive, since antibodies to particular agents
can be found in the bloodstream long after that infectious agent is
gone.  (How long depends on the patient and the agent involved, but
it is usually measured in years.)

Even if a direct test were used, other possibilities exist.  The test
could have been improperly administered.  The positive could have been
a false positive, the result of innocent cross-reacting proteins that
were no longer present when the second test was done.  The test results
could have been interpreted under different standards (which vary from
country to country -- sometimes even from lab to lab!).