According to the CDC website, "The CDC estimates that gay and bisexual men account for just 2% of the U.S. population, but accounted for 61% of all new HIV infections in 2009. They are 49% of the people living with HIV infections in 2008."
Since the FDA is a US department, they are concerned with the US and not the world. Gay and bisexual men are the largest group affected here.
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