On Monday, the U.S. Food and Drug Administration approved a HIV drug named Truvada, that may help healthy people by preventing them from contracting the virus that causes AIDS. Truvada has been on the US market since 2004 as a treatment for people infected with HIV to be used in combination with other antiretroviral drugs. The pill has been hailed by some AIDS advocates as a potent new tool against human immunodeficiency virus, but some health care providers are concerned it could encourage risky sex behavior.