VANCOUVER, British Columbia — At 12 tables, in front of 12 mirrors, a dozen people are fussing intently in raptures of self-absorption, like chorus line members applying makeup in a dressing room.

But these people are drug addicts, injecting themselves with whatever they just bought on the street — under the eyes of a nurse here at Insite, the only “safe injection site” in North America.

“You can tell she just shot cocaine,” Thomas Kerr, an AIDS expert who does studies at the center, said of one young woman who keeps readjusting her tight tube top. “The way she’s fidgeting, moving her hands over her face — she’s tweaking.”

Insite, situated on the worst block of an area once home to the fastest-growing AIDS epidemic in North America, is one reason Vancouver is succeeding in lowering new AIDS infection rates while many other cities are only getting worse.