Internet Use and Early Syphilis Infection Among Men Who Have Sex with Men --- San Francisco, California, 1999--2003 During the summer of 1999, an outbreak of early syphilis among men who have sex with men (MSM) who met their sex partners on the Internet (1) presaged a rapidly expanding syphilis epidemic in San Francisco. By 2002, San Francisco had the highest rates of primary and secondary syphilis of any metropolitan area in the United States (2). During 1998--2002, the number of early syphilis cases increased, from 41 cases in 1998 to 495 cases in 2002 (3). Concomitant with the increase...