The United Nations organization released disturbing estimates Thursday of the seemingly relentless expansion of the HIV pandemic. At a time when many Americans are increasingly optimistic that state-of-the- art drug therapy might eliminate the virus, HIV is taking a heavy toll worldwide. According to the agency, every minute of every day somewhere in the world, six people become infected with HIV: 7,500 adults per day and 1,000 children. About 30 million people have acquired the virus during the last 15 years; 6.4 million of them have died ....