Chlamydia: an overview and more Sexually transmitted diseases (STDs), also known as sexually transmitted infections (STIs), are sexually transmitted diseases. STDs can be bacterial, like chlamydia and gonorrhea, or viral, like herpes, HIV, and HPV. Related Articles Paclitaxel (with polyoxyethylated castor oil) Injection Summary of drug information Summary of consumer health information Summary of the effect on breastfeeding