Caused by bacteria
Chalmydia. No symptoms may occur at first or at all, especially in women. Later symptoms for women may include itching around the vagina, a yellow, odorless discharge from the vagina, pain during sex, and needing to urinate often or having pain when urinating. Women may also have bleeding between periods or dull pain in the pelvic area. Symptoms for men may include pain or burning when urinating and a watery, milky-colored discharge from the penis.
Gonorrhea (or "the clap" or "the drip"). Men may have a thick, yellow discharge from the penis and pain when urinating. The opening of the penis may be sore. Gonorrhea doesn't cause symptoms in most women. When symptoms do occur, women may have white, green or yellow discharge from the vagina, pain when urinating, spotting between periods, or heavy bleeding during periods. Sometimes fever and abdominal pain occur. Gonorrhea can cause sore throats in people who have oral sex or can cause pain in the anus in people who have anal sex.
Syphilis. Early signs include a chancre (a painless, red sore). The sores may appear where you were touched during sex, including your genitals, anus, tongue and throat. The glands near the chancre may swell. A few months later, you may have a fever, sore throat, and headache, not feel hungry or have joint pain. A scaly rash may appear on the palms of your hands and the soles of your feet. After these symptoms pass, you may not have any symptoms for a number of years. When the symptoms return, the infections can affect the brain, spinal cord, and skin and bone.
Caused by viruses
Hepatitis B. Symptoms may include muscle aches, fever, tiredness, loss of appetite, headache and dizziness. As the disease worsens, you may have dark urine, loose, light-coloured stools, yellow eyes and skin, and tenderness in the liver area (just below the ribs on the right side). Hepatitis B can be fatal if it leads to liver failure or liver cancer.
Herpes. Symptoms start with tingling or itching around your genitals. Small blisters may form in the area and then pop open. When this happens, you might feel burning, especially when urinating. The sores then turn to scabs. During the first outbreak, you might have swollen glands, fever and body aches. But some people don't have such obvious symptoms. Outbreaks may occur for the rest of your life, but usually become less frequent and less painful with time.
Human immunodeficiency virus (HIV). HIV is the virus that causes AIDS (acquired immunodeficiency syndrome). It weakens your body's ability to fight off disease. As your body's immune system weakens, illnesses begin to develop until you can no longer fight them off. Symptoms may take years to develop and may include unusual infections, unexplained fatigue, night sweats and weight loss.
Human papillomavirus (HPV). HPV may cause a growth of soft, flesh-coloured warts around the genital area or on the cervix. The warts are painless, but may be bothersome because of the way they look. Sometimes the virus causes warts that can't be seen by the naked eye. There is a link between HPV and cancer of the cervix.