The Front man for MTV's anti-AIDS crusade this year will be P. Diddy, the rap entrepreneur formerly known as Puff Daddy and still occasionally known as Sean Combs. On Dec. 1, World AIDS Day, the music network will air a documentary titled "Staying Alive" to over 365 million households in 139 countries, with other broadcasters taking it to 200 million more households. "HIV and AIDS touches everyone. It kills without conscience, rich or poor, black or white, young or old," said Combs, former boyfriend of Jennifer Lopez. "More than ever before, we need to focus on what unites us, not divides us." In keeping with the international spirit, the documentary does interviews with AIDS victims from Stockholm to Phnom Penh, providing a rare sober note amidst the music channel's usual pursuit of hedonism. "With young people accounting for 50 percent of new HIV infections, MTV will continue to dedicate its airwaves . . . to communicating prevention, anti-discrimination and awareness messages to help them avoid infection," said Bill Roedy, president of MTV Networks International. Ricky Martin was the safe sex spokesman last year.