BACKGROUND Since the first AIDS cases were reported in 1981, through mid-1994 more than 402,000 AIDS cases and more than 241,000 deaths have been reported in the United States alone. This is only the tip of the iceberg of HIV infection, however. It is estimated that nearly 1 million Americans had been infected with the virus through the mid-1990s but had not yet developed clinical symptoms. In addition, although the vast majority of documented cases have occurred in the United States, AIDS cases have also been reported in almost every country ....