This document discusses sexually transmitted diseases (STDs), also known as sexually transmitted infections (STIs). It notes that 448 million new curable STI cases occur annually worldwide, including syphilis, gonorrhea, chlamydia, and trichomoniasis. STIs can exist without symptoms and lead to infertility, ectopic pregnancy, stillbirth, neonatal death, and increased HIV risk if left untreated. The document outlines common bacterial, viral, and parasitic STIs and recommends abstinence or mutual monogamy for prevention or consistent condom use to reduce transmission risk.