Transmission of syphilis
Since T. pallidum (syphilis) rapidly dies off outside the body, infection requires direct passage from one organism to another, i.e. through mucous membrane contact of any kind, most frequently through sexual intercourse. The pathogen can also enter the new host through the uninjured mucosa, whereby contact with the mucosa for less than one minute can be sufficient. The pathogen can also penetrate through the injured skin, but not through the uninjured skin.
The risk of transmission upon contact with an infected person is probably 30-60%. Highly infectious are patients in stage I of syphilis, where the risk of transmission is 100%. In stage II of syphilis, patients are infectious and in stage III, despite severe symptoms, there is no longer any risk of infection (no transmission).
More information about the individual stages can be found here: Syphilis SymptomsMain sources of infection are the weeping skin lesions of the early secondary stage in diseased sexual partners, they contain abundant pathogens. Non-sexual transmission is also possible, e.g. through a kiss, by obstetricians, dermatologists or blood transfusion. In addition, T. pallidum is placental, i.e. the bacterium can enter the child’s bloodstream via the placenta during pregnancy or from the mother’s bloodstream at birth, thus infecting the child.
A single bacterium is probably sufficient for infection/transmission. After the bacterium enters the body, it spreads and infects the body in the stages of incubation, generalization and organ manifestation. During incubation, T. pallidum actively penetrates the tissue due to its mobility and forms a primary complex with swollen regional lymph nodes.
During generalization, the bacterium spreads via the bloodstream (hematogenic). It is assumed that T. pallidum is able to loosen the walls of small arteries by an enzyme so that it can better penetrate the vessel. This leads to inflammation and a narrowing of small arteries, which results in a reduced supply of oxygen to the tissue and thus to tissue death (necrosis). This organ manifestation manifests itself in the secondary and tertiary stages.
