Over the past 15 years, some 2,000 positive men worldwide have fathered HIV negative kids using a technique called sperm washing. Sperm (which is generally believed, but not proven, to be HIV-free) is spun in a centrifuge, separating it from the infectious semen. It’s then extracted and frozen until insemination. Out of thousands of rinse cycles, not a single woman or child has contracted HIV when this process was used. But reproduction experts may still want a foolproof technique for determining that the initial sperm is indeed HIV-free.

Enter some Japanese scientists, who say they can prove just that—with a method sensitive enough to detect even a single particle of HIV genetic material. The group has also finessed the separation technology to further reduce the risk of sperm mixing with HIV after washing.

The process isn’t cheap; like fertility treatments, it can run to tens of thousands of dollars. But insurance often covers at least part of the bill (learn more at www.bedfordresearch.org). The cigar’s on us.