Direct contact with a ____ sore, called
a chancre, can lead to transmission. The infection
may begin with a round, firm, painless sore located
on the penis, vagina, anus, or mouth. Sometimes,
these sores go unnoticed, because they are
painless, and then symptoms clear. However, the
infection continues to advance, during this stage. If
untreated, later stages of the disease can damage
the heart, blood vessels, liver, bones, joints, and
skin