This fall the CDC launched its “STARHS Strategy”—an HIV test designed to differentiate “old” infections (more than four months) from “new” ones (129 days or less). STARHS, or “Serologic Testing Algorithm for determining Recent HIV Seroconversion,” could make it easier for HIVers to estimate when—and name from whom—they got the big bad bug.

Yet identifying the source of infection and tracing potentially exposed partners remain dicey issues, said Willi McFarland, director of HIV sero-epidemiology for San Francisco, the only city currently implementing the test. Partner-notification laws differ from state to state, but San Francisco uses a voluntary approach as part of risk-assessment counseling. The health department can also track down partners anonymously for clients, though “very few take us up on the offer,” said McFarland.

STARHS is a double header—it uses two different ELISAs to test one blood sample. A positive result on the common HIV test—an upgraded version of the ELISA used since 1984—can pinpoint an infection within the past three weeks. A positive on the new “detuned” ELISA tags an infection at least four months old. Translation: A poz/neg result spells recent infection; a double pos means an older one.

Steven Gibson, director of the STOP AIDS Project in San Francisco, said the new testing method scares up some prickly questions. “The biggest concern in terms of naming partners is that political winds can change,” he said. “How can we ensure privacy?” Things get even stickier in states where HIVers who knowingly have unprotected sex face felony charges, said Gibson. Given that PEP, or postexposure prophylaxis, is effective only within 72 hours of seroconversion and early intervention with anti-HIV drug therapy is hotly debated, STARHS’ health-tool status may be a false positive.