Ride a Metrobus these days and you’re likely to be confronted with an astounding statistic, courtesy of Whitman-Walker Clinic’s latest fundraising campaign, in use since October: “For every 20 D.C. residents on this bus, 1 of them has HIV*,” read ads on the back and interiors of many District buses, followed by a Web address, a phone number, and instructions to “give to Whitman-Walker Clinic today.” The asterisk, though, points to a disclaimer that suggests that the figure is by no means exact. The fine print explains that one District resident out of 50 has AIDS, according to a DC Appleseed Center for Law and Justice report—but offers no explanation of where the higher HIV rate comes from. Is there some undisclosed link between riding a Metrobus and HIV infection? No, says Chip Lewis, a clinic spokesperson; the figure is based on an extrapolation. “HIV and full-blown AIDS are two different things,” he says, and the 1-in-20 figure is the Appleseed Center’s best guess based on the national proportion of those with HIV to those with AIDS. Best guesses aside, the fundraising drive, says Lewis, has led to a healthy bounce in donations: “It’s a very striking ad campaign.” —Ryan Grim