Sexually Transmitted Diseases (STD) There are now more than twenty disorders recognized as being transmitted primarily by sexual means. The more familiar STD's are AIDS, gonorhea, syphilis, chlamydia-related infections, genital herpes, candidiasis, nonspecific vaginitis, trichomoniasis, pediculosis, scabies, and urinary tract infections. GONORRHEA One of the most frequently encountered communicable diseases in the U.S. It is caused by the bacterium Neisseria Gonorrihoeae, which is common all over the world today and can only thrive in human beings.