Third-stage syphilis is infectious, but its contagiousness is relatively weak compared to first-stage and second-stage syphilis. The titers detected in third-stage syphilis are usually lower, so its infectiousness is comparatively minor. However, third-stage syphilis still has the capability to infect others. Therefore, patients with third-stage syphilis must actively seek treatment and refrain from having sexual relations with others, while also enhancing their own immunity.