What is the primary sign or symptom observed during the primary phase of a Syphilis infection?

The primary sign of syphilis during its initial stage is the presence of a chancre, which is a painless ulcer that typically develops at the site where the Treponema pallidum bacteria enter the body, often in the genital region. This lesion is usually solitary, firm, round, and has a raised border. It appears about three weeks after exposure and is a hallmark feature of primary syphilis, making it a key diagnostic indicator.

While fever, rash, and swollen lymph nodes can occur in other stages or phases of syphilis or may accompany other infections, they are not defining characteristics of the primary stage. Fever may be present but is nonspecific. Rash generally appears in secondary syphilis rather than primary, and swollen lymph nodes can occur but are more common during the secondary phase, when systemic spread is more apparent. Thus, the chancre is distinctly associated with the primary phase of syphilis, serving as the primary clinical manifestation of this initial infection stage.