From the AIDS.gov blog:

Trend data released today in CDC’s 2011 STD Surveillance Report show that primary and secondary syphilis rates are increasing among gay and bisexual men, who now account for more than 70% of all infections.

Annual syphilis surveillance data published in the just released 2011 STD Surveillance Reportcontinue to emphasize the disproportionate burden of disease among gay and bisexual men. While the health problems caused by syphilis in adults are serious in their own right, it has been shown that the genital sores caused by syphilis make it easier to transmit and acquire HIV infection sexually. There is an estimated 2- to 5-fold increased risk of acquiring HIV if exposed to that infection when syphilis is present, and studies have also shown that syphilis will increase the viral load of someone who is already HIV infected. This is especially concerning, as data from several major cities throughout the country indicate that an average of four in 10 MSM with syphilis are also infected with HIV. The stakes are too high to ignore these health disparities. It is critically important that syphilis infections among MSM be promptly diagnosed and treated in order to decrease the rates of subsequent HIV infection.

Read more on AIDS.gov.