Chlamydia is an under-reported, mostly asymptomatic but very serious disease

"Chlamydia is a sexually transmitted disease that is caused by a bacteria called Chlamydia trachomatis, and it is nasty. It's not widely recognized in popular channels in the United States because other STDs that cause more severe symptoms attract all the attention. You see, chlamydia can be asymptomatic (without symptoms) in many of those infected. Nevertheless, its consequences can be very dramatic. Anything from pelvic inflammatory disease in women, where the uterus and fallopian tubes are infected and can be permanently damaged, and infertility in men can happen with a chlamydia infection."