A study suggests encouraging drug abusers to use thin syringes, which retain less fluid and the virus it may contain.

Distributing “low-dead-space syringes” to addicts could substantially lessen H.I.V. transmission among them, a new study has estimated.

Syringes have widely varying amounts of “dead space” — the amount of fluid retained even when the plunger is fully depressed, said William A. Zule, a researcher at RTI International and the lead author of the paper in The International Journal of Drug Policy.