Chlamydia: often described as a silent infection as most people do not have obvious signs. Symptoms can include pain when urinating, unusual discharge from the vagina, penis or rectum. Women may get pain in the tummy, bleeding during or after sex and in between periods, while men can have pain and swelling in the testicles.
Gonorrhoea: some people have no symptoms, but those who do may have a yellow or green discharge; a burning sensation when they wee and pain or tenderness in the stomach.
Syphilis: many people won't have symptoms. But for those that do, it will start with a small, painless ulcer in the mouth or genitals, followed by a rash. If left untreated, the infection can result in visual impairment, dementia and death. In pregnancy it can also lead to miscarriages, still births and infant mortality.
Herpes: again, some people have no symptoms, but they can include small blisters that burst to leave red, open sores around the genitals, rectum, thighs and buttocks. Blisters and ulcers can also be on the cervix; it can cause vaginal discharge, pain when having a wee, as well as general flu-like symptoms.
Genital warts: in women they start as small, gritty-feeling lumps that become larger. In men the warts will feel firm and raised, with a rough surface. They can be single warts or grow in clusters.