Sexually transmitted diseases (STDs) are passed by sexual contact with another person. STDs can be caused by bacteria, viruses, or parasites.
Chlamydia is caused by bacteria and is one of the most common sexually transmitted diseases among young people. It affects the urinary tract and the genitals. If left untreated, it can lead to pelvic inflammatory disease. Chlamydia does not have very obvious warning signs or symptoms, so often, this disease will get left untreated.
Pelvic inflammatory disease, also known as PID, can be caused by bacteria such as chlamydia or gonorrhea. If either of these two diseases goes untreated, they can lead to pelvic inflammatory disease, which can lead to sterility or menstrual problems. Sterility is the inability to reproduce. In men, this means an inability to fertilize oocytes; in women, this is either an inability to produce healthy oocytes or an inability to gestate a baby.
Gonorrhea is another disease that is caused by a bacterium. Diseases that are caused by bacteria can be treated with antibiotics. Sometimes they are hard to detect because the warning signs aren't obvious. In males, gonorrhea will cause painful urination, oozing from the penis and, if it's left untreated, can cause sterility. In women, the symptoms are very hard to notice, and often it will go untreated, which can then lead to sterility.
Syphilis is also caused by bacteria that causes ulcers or chancres (painless genital ulcers) on the skin. Syphilis can affect various organs of your body, such as your bones and heart. If left untreated, it can lead to insanity and paralysis. This one, again, can be treated with antibiotics if caught early.
Genital herpes is caused by a virus. There is no cure for genital herpes. Periodically, sores will develop on the genitals.
Genital warts is when warts or growths will develop on the genitals. This is the result of HPV. HPV stands for Human Papilloma Virus.
Hepatitis B and Hepatitis C are viruses that are transmitted through body fluids, such as blood or semen. This type of virus will attack the liver and inhibit the liver's ability to properly function; it can be a very serious disease.
Trichomoniasis is a disease that's caused by a parasite. Trichomoniasis leads to the urethra becoming inflamed, which can cause painful urination. However, this disease can be treated with antibiotics.
Source: This work adapted from Sophia Author Amanda Soderlind.