After syphilis spirochete infection, the disease usually develops 2-3 weeks after infection, and the initial onset of the disease usually has mild systemic symptoms or no obvious symptoms. The erythema is mainly on the genitals, which can become necrotic and form an ulcer, which is usually 1-2 cm in diameter, round or oval, and is usually painless, and is clinically referred to as the chancre. The erythema is clinically referred to as the chancre, which can last for 3-4 weeks and, with effective treatment, can last for 1-2 weeks before subsiding. After the erythema subsides, a reddish-brown scar may remain, or the skin may become darker in color, and 1-2 weeks after the chancre has appeared, the inguinal lymph nodes may become enlarged, or the lymph nodes may become enlarged in the affected area, which is the most contagious and is known as the first stage of syphilis.