There are only about 20,000 new syphillis cases per year; it is one of the least common STDs in the US, less than half the frequency
of new HIV
infections. And most of the new syphilis cases, like HIV, occur in gay/bi men, and the heterosexually acquired cases are pretty much limited to just a few geographic areas. Following that theme, the chance that syphilis is present in a woman who is not a commercial sex worker, and especially a colleague at a business conference, is almost zero.