Chlamydia is an infectious disease caused by the bacterium Chlamydia trachomatis and trasmitted through sexual contact and childbirth. According to the WHO, there are an estimated 131 million people newly infected with chlamydia each year. Complications of infection include epididymitis in men, pelvic inflammatory disease in women, and a greater risk factor for HIV. Chlamydia is readily treated with antibiotics such as doxycycline, azithromycin, and erythromycin. There is no approved vaccine.