Genital herpes is caused by two types of herpes simplex virus: type 1 (HSV-1; the cause of cold sores of the lips and mouth) and type 2 (HSV-2). The disease first appears as groups of small blisters on the surface of the penis in men and the vulva in women. The initial infection clears spontaneously within two to three weeks, but herpes commonly recurs with varying frequency thereafter, burning or itching at the infection site containing the lesions. Herpes is generally transmitted only when an active lesion is present; it can be prevented by avoidance of intercourse during the active phase. The risk of transmission is diminished by the use of a condom. Active herpes can be fatal to infants during delivery; in a large percentage of cases, it causes blindness or brain damage in newborns. In women, genital herpes has also been associated with cervical cancer. Antiviral treatment early in the course of the disease may decrease the duration of symptoms.

Another common herpesvirus, cytomegalovirus (CMV), is associated with high mortality in persons with weakened immune systems.

Chancroid

Chancroid, also called soft sore, is caused by the microorganism Haemophilus ducreyi and occurs chiefly in developing countries. The bacteria has a short incubation period, producing small red pustules generally within fewer than five days after exposure; the pustules burst to form painful ulcers, and the disease can be diagnosed by culturing bacteria from these ulcers. Unlike syphilis, which it may resemble, chancroid is a purely localized disease of the genitals. Treatment is with antibiotics.

Lymphogranuloma venereum

Lymphogranuloma venereum, which is common in the tropics but very rare in temperate regions, is caused by Chlamydia trachomatis. It is usually transmitted through intercourse but may be contracted in other ways. Typically, a transient genital blister is followed by regional inflammation of the lymph nodes. If untreated, this condition may progress to genital elephantiasis. Treatment is with broad-specturm antibiotics. Surgical removal of diseased tissue may be necessary.