This article was last reviewed on
This article waslast modified on 26 July 2023.

There are more than 20 known sexually transmitted diseases (STDs). Some of them will cause symptoms that should be brought to the attention of a doctor immediately. However, some of these STDs can be "silent" — a person could have the disease but might not notice any symptoms of the infection. Therefore, it is important to be tested for STDs if you take part in unprotected oral, genital, or anal sex. If left untreated, STDs can go on to cause complications, such as pelvic inflammatory disease and infertility, cause infection elsewhere in the body, and can also cause infections in neonates if passed from mother to baby during pregnancy.

The most common STDs are listed below:

  • Gonorrhoea. This bacterial infection, caused by Neisseria gonorrhoeae, at first may cause a slight discharge from the vagina, penis, or anus. However, 50% of women and 10% of men with gonorrhoea have no symptoms at all. If the infection is not treated, it can lead to sterility and other complications, including disseminated gonorrhoea where it can infect other parts of the body, however this is rare. Gonorrhoea can be diagnosed through polymerase chain reaction (PCR), also termed nucleic acid amplification tests (NAATs), or culture, using selective media. Treatment for gonorrhoea involves antibiotics which can be given orally or through an injection.
  • Chlamydia. Chlamydia trachomatis is often called "the silent epidemic" because infections are common yet many people do not realize that they are infected. Only one in four of infected people have symptoms of a slight discharge and stinging on passing urine. It is the commonest STD in the UK, with high prevalence in people under 25. This bacterial disease is easily cured with antibiotics but can have serious health consequences if left untreated. Again, NAATs can be used for diagnosis and laboratories normally test a panel of STDs using this method.
  • Syphilis. Syphilis is a bacterial infection caused by Treponema pallidum that can be easily missed. Syphilis infection occurs in different stages, the first symptom is a painless blister or sore that will disappear on its own, but the infection can be passed on to others for up to eighteen months. At this stage, syphilis can be treated with antibiotics with few adverse effects. However, if left untreated, the disease can spread throughout your body over the course of many years and cause considerable organ damage. Diagnosis of syphilis can be achieved through serological testing. Laboratories rely on serological tests as other methods, such as dark ground microscopy and culture, require a lot of expertise and time and may not be as sensitive.
  • Trichomonas. Trichomonas vaginalis is a microscopic parasite that can cause symptoms of watery discharge and stinging on passing urine. Upon cervical examination, it causes a characteristic ‘strawberry cervix’ in females resulting from irritation and capillary haemorrhage on the cervical surface. Treatment is available, usually involving the oral antibiotic Metronidazole. Diagnosis can be achieved through many methods. Trichomonas may be a pathogen that is offered on a NAAT panel. It can also be identified through microscopy, using either specialised stains or wet mount, where the sample is placed on the slide, covered with a cover slip and examined using light microscopy. Culture can also be performed using specialised liquid media which can then be examined under light microscopy for the parasite.
  • Human papillomavirus (HPV). This virus can infect the genital area, causing genital warts (condylomata). Some types of the virus have been associated with cervical cancer. Early detection with cervical smear testing can limit the risk of cancer and vaccines are now widely available against this virus.
  • Genital herpes. Herpes simplex virus 2 (HSV2) causes recurrent, periodic outbreaks of sores in the genital region and remains in your body for life. However, there are anti-viral therapies available that can shorten the duration of symptoms.
  • Hepatitis B and Hepatitis C. These are viral infections that can be transmitted through sexual contact. Hepatitis B and C affect the liver and can severely damage it. Treatment with interferon is available, but this drug therapy may have serious side effects.
  • Human Immunodeficiency Virus (HIV). HIV is associated with AIDS. Initially, patients may report a flu-like illness which is typical when first exposed. This virus then multiplies and attacks and destroys certain white blood cells (T-helper lymphocytes) that are involved in the immune system. As the number of these cells is reduced, the ability of your body to fight off infections also decreases, meaning patients may be more susceptible to opportunistic infections which do not usually cause disease when healthy. There is no cure but early detection allows for lifelong treatment with anti-viral therapies that can help to prolong life and reduce the instance of secondary infections resulting from the depleted immune system.

You can refer yourself to any Sexual Health Clinic in the UK to receive free, confidential testing and treatment. Your GP is not informed without your permission and your samples are usually anonymised. For any sexually transmitted disease, an infected person should inform their recent sexual partner(s) so that they may be treated as well, termed contact tracing. Clinic staff will advise you how best to do this, but it is not compulsory.