Humans are the only reservoir and, apart from congenital cases, the only epidemiologically relevant mode of transmission is by direct contact with treponema-rich, open lesions and contaminated secretions from a patient.
Ljudje so edini rezervoar, poleg kongenitalnega načina je edini epidemiološko relevanten način prenosa neposredni stik z odprtimi razjedami, v katerih je prisotna treponema, in kontaminiranimi izločki bolnika.