AIDS (Acquired Immune Deficiency Syndrome): Caused by the HIV virus. This condition progressively reduces the effectiveness of the immune system and leaves individuals susceptible to opportunistic infections and tumors. AIDS is now a pandemic. Although treatments for AIDS and HIV can slow the course of the disease, there is currently no vaccine or cure. Gonorrhea: Caused by the bacteria Neisseria gonorrhoeae. Symptoms in women can include pelvic inflammatory disease (PID), include cramps and pain, bleeding between menstrual periods, vomiting or fever. Men may complain of pain on urinating and thick, copious, urethral pus discharge. Men have a 20 percent chance of getting the infection by having sexual relations with a woman infected with gonorrhea, whereas women have a 50% chance of getting the infection by having sexual relations with a man infected with gonorrhea. Instances of blurred vision in one eye may occur in adults. Gonorrhea can generally be treated with antibiotics, although antibiotic-resistant strains are known to exist. Chlamydia: Caused by the bacterium Chlamydia trachomatis. Chlamydia is a major infectious cause of human genital and eye disease, and is one of the most common sexually transmitted infections worldwide. Between half and three-quarters of all women who have a chlamydia infection of the neck of the womb have no symptoms and do not know that they are infected. In men, infection of the urethra is usually symptomatic, causing a white discharge from the penis with or without pain on urinating. Occasionally, the condition spreads to the upper genital tract in women (causing PID) or to the epididymis in men (causing epididymitis). If untreated, chlamydial infections can cause serious reproductive and other health problems with both short-term and long-term consequences. Chlamydia is treatable with antibiotics. Syphilis: Caused by the Treponema pallidum bacteria. The signs and symptoms of syphilis are numerous; before the advent of serological testing, precise diagnosis was very difficult. Syphilis can generally be treated with antibiotics, including penicillin. If left untreated, syphilis can damage the heart, aorta, brain, eyes and bones. In some cases these effects can be fatal. Genital herpes: Caused by Herpes simplex viruses. Infection with the herpes virus is categorized into one of several distinct disorders based on the site of infection. Genital herpes is often asymptomatic, though viral shedding may still occur. After initial infection, the viruses move to sensory nerves, where they reside as life-long, latent viruses. Causes of recurrence are uncertain, though some potential triggers have been identified. Over time episodes of active disease reduce in frequency. There is currently no cure. However, treatments are available to reduce viral reproduction and shedding, prevent the virus from entering the skin, and alleviate the severity of symptomatic episodes.