Zackie Achmat, a South African who is a leading proponent of an international solution to the AIDS crisis, was in New York this week, just as his government at long last delivered on the demands that he and other activists have pushed for years - that it develop a comprehensive treatment plan for its 4.5 million citizens living with HIV. Achmat was blistering in his critique of the failure of world leaders to confront the scourge of HIV. At the top of his list was the American president. "The greatest threat to public health in the world is George Bush staying in power," he said.