Approximately one third of Sexual Contacts of Infectious Syphilis will develop the disease. The transmission rates have been reported as 10 to 60%

Following contact, T. pallidum invade through the
mucosal surface or abraded skin and divide at the
point of entry to produce the chancre of primary disease.
This incubation period is typically 21 days
(range 9–90), but is dependent on infectious dose –
larger doses resulting in ulcers more quickly