On Thursday, CDC reported that increases in new HIV infections have yet to follow earlier outbreaks of syphilis among gay and bisexual men in Los Angeles and San Francisco. However, there is still a steady annual increase in HIV infections, including 13 percent among one group of men studied, CDC reported.

In San Francisco, syphilis cases leapt among gay and bisexual men from four cases in 1998 to 260 in 2002. And new Los Angeles cases among this population jumped from 67 in 2000 to 299 in 2002. With these outbreaks indicating unprotected sex practices and other behaviors that can spread both STDs, CDC officials predicted a rise in HIV rates would soon follow. In addition, there is evidence that having an STD such as syphilis can make it easier to acquire HIV.

The 1998-2002 study, CDC said, "indicated that, as of 2002, the outbreaks of syphilis had not had a substantial impact on HIV incidence among [gay and bisexual men] in these two cities." "Whether the syphilis outbreaks are sentinel events indicating increased risk behavior that could eventually result in increased HIV incidence is not known."

CDC noted its statistics were incomplete because some men with syphilis refused to be tested for HIV. The full report, "Trends in Primary and Secondary Syphilis and HIV Infections in Men Who Have Sex with Men - San Francisco and Los Angeles, California, 1998-2002," is published in Morbidity and Mortality Weekly Report (2004;53(26):575-578).