Through chancres, not semen. A positive test for syphilis can mean syphilis, but it can also mean a prior treated case of syphilis, or sometimes other, nonsexual diseases can cause the syphilis test to be "false positive." I am sure that the doctor who ordered the syphilis test knows this and would recommend a follow-up test to find out what to do next. You should be working with a doctor on this, not trying to research it yourself. Please look into this at once.
Thank you.
Dr. Rockoff