Deadspace...

This article is an interesting take on lessening exposure to HIV for IV drug users.  It's quite simple actually, the less deadspace a syringe has, the less it can hold, therefore the less HIV virus can be in the container.  Deadspace is the amount of fluid retained in the syringed when it is fulled plunged.  

Basically, this is limiting the amount of backwash.  The larger syringes have 40X or more deadspace than smaller ones like those used by diabetics.  That means the larger syringes up your odds 40X, due to sheer volume of exposure.

This won't prevent transmission of the virus, but it might limit it due to amount of exposure.  You're still playing Russian Roulette, but your forcing the bullets through a smaller nozzle.

I'm not sure what I think of this one, but it is a novel take on the matter.

Cya...