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View Diary: Out of Africa: The Origins of HIV (29 comments)

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  •  I'm talking about the concept (1+ / 0-)
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    insofar if a certain percentage of the population can be kept from being infected, the spread will be reduced . . .

    and maybe reach a tipping point and be eliminated.

    •  I see what you mean, but that's not herd immunity (1+ / 0-)
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      Roadbed Guy

      I suppose what you mean is that if everyone who was not in a long-term monogamous relationship used a condom, etc., every time they had sex, then HIV wouldn't spread even if some small % of the population was not protected.  The problem is that the people who don't use protective measures tend to associative, at least as far as their sexual and needle-sharing partners go.  In that case, the infection cycle will continue indefinitely.  Those folks are running with the wrong herd.

      •  I should probably brush up on the exact (0+ / 0-)

        meaning of "herd immunity" to be sure - I was partly going on the premise that natural immunity might work into the concept (but I could be wrong about that!).

        •  Natural immunity can work two ways (1+ / 0-)
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          Roadbed Guy

          One: There may be a group of people who just do not get infected when they are exposed to HIV.  In this case it is hard to separate out natural immunity from "inadequate" exposure.  Just because you had unprotected sex with an HIV-infected person does not mean you were exposed in a way likely to lead to infection (no one wants to say this of course, and I don't advocate it).  Same with needle sticks, etc.  Lack of infection does not always mean natural immunity.  If someone truly does have natural immunity that prevents infection, then that trait would certainly be very important for effective herd immunity.  But I do not believe that this primary natural immunity plays a large part in the natural history of HIV.

          Two:  There is the apparent natural immunity of those who are infected but never become sick.  This is rare, but is the focus of some very intensive research.  While certainly useful for those endowed with a secondary natural immunity like this, it may not be useful in controlling disease spread because the person could be perfectly healthy yet still be infectious.  No one knows at this point.  

          A good, cheap, and easy-to-store vaccine that prevents primary HIV infection would change the world.

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