Nearly half are unaware of their infection-CDC
* CDC calls for renewed HIV prevention efforts
(Adds CDC interview, other comments)
By Julie Steenhuysen
CHICAGO, Sept 23 (Reuters) - Nearly one in five gay and bisexual men in 21 major U.S. cities are infected with HIV, and nearly half of them do not know it, U.S. health officials said on Thursday.
Young men, and especially young black men, are least likely to know if they are infected with HIV, according to a study by the U.S. Centers for Disease Control and Prevention.
"We need to reinvigorate our response to preventing HIV among gay and bisexual men," Dr. Jonathan Mermin, director of CDC's Division of HIV/AIDS Prevention, said in a telephone interview.
"We can't allow HIV to continue its devastating toll among gay and bisexual men, and in particular, among young black men."