Sexually transmitted infections

What are the main STIs?

The ten most common STIs in the UK are:

• Anogenital warts.

• Chlamydia.

• Genital herpes.

• Gonorrhoea.

• Human immunodeficiency virus (HIV).

• Hepatitis B.

• Hepatitis C.

• Pubic lice.

• Syphilis.

• Trichomonas.

There are some other STIs that are uncommon in the UK - for example, donovanosis and chancroid.

A 2023 report from UK Health Security Agency (see Further Reading below) reported:

• The impact of STIs is still greatest in those aged 15 to 24 years, gay, bisexual and other men who have sex with men and some minority ethnic groups.

• The most commonly diagnosed STI was chlamydia, which accounted for nearly half (48%) of all new STI diagnoses.

• Gonorrhoea accounted for about 1 in 5 new diagnoses.

• Syphilis diagnoses increased 9.4% and there was a larger proportional increase in syphilis diagnoses among heterosexual men and women than among gay, bisexual and other men who have sex with men.

Some other infections may be mistaken for STIs because they can either affect the genital region or can be passed by any close contact, including but not only during sexual contact. Examples include:

• Scabies.

• Molluscum contagiosum.

• Cystitis.

• Bacterial vaginosis.

• Monkeypox.

Symptoms of each STI can vary, from local symptoms affecting the genitals, to symptoms that affect various other parts of the body. The following is not a full list of all possible symptoms. However, these are the common symptoms to look out for:

• A vaginal discharge.

• Abnormal vaginal bleeding.

• A discharge from the penis.

• A sore, ulcer, rash, or lump that appears on the penis or around the vagina, vulva or back passage (anus).

• Pain when you have sex.

• Pain when you pass urine (although the common reason for this is a urine infection and not an STI).

• Swelling of the glands in your groin.

But remember, in many cases of STI, no symptoms may develop. However, you can still pass on the infection to others even if you have no symptoms. Therefore, if you think that you may have an STI, it is best to get it checked out.

If you have a symptom that you think is due to an STI, or if you have no symptoms but are worried you have caught an STI then you should see a health professional.

You can:

• Contact your own doctor. Your doctor can give advice and may examine you. However, if your doctor suspects that you may have an STI, in the UK they are likely to refer you to a GUM (genitourinary medicine) clinic. Some doctors may do tests and manage the situation without a referral to a GUM clinic; or
  

• Go to a GUM clinic directly. In the UK you do not need a referral from your doctor to go to a GUM clinic. You can find out details of your nearest Sexual Health clinic from our self-referral tool "Refer Yourself to NHS Sexual Health Services".

Until you are checked out, and treated if necessary, you should not have sex. This is to prevent you passing on any infection.

Depending on the initial assessment and examination, the doctor may advise on some STI tests and ask for your consent to do the tests. Learn more in the separate leaflet called STI tests.

If you are diagnosed with an STI then the clinic will encourage you to tell any current or recent sexual partners that you have an infection. You are not obliged to do this or to give out any information about other people. However, it is best that any recent sexual partners should know that they might also be infected. They should be offered testing and treatment if necessary, to prevent the infection being spread any further. This telling of sexual partners is sometimes called contact tracing. If you prefer, clinics can contact people anonymously if you do not wish to tell them yourself. You should be aware that recklessly exposing a sexual partner to the risk of infection is against the law.

The treatment that you will be offered depends on which STI is found. For example:

• A short course of antibiotics can usually clear away chlamydia, gonorrhoea, syphilis and trichomonas.

• A cream or lotion can clear pubic lice and scabies.

• Topical treatments can usually clear most anogenital warts.

• Treatments for genital herpes, hepatitis B, hepatitis C and HIV are more involved and complex. You will be given advice about what treatment options you have and given time to ask questions.

If you are prescribed antibiotics then it is important to finish the full course of tablets, or else the infection may not be fully cleared. If you develop side-effects then seek advice from the GUM clinic or from your doctor as to what to do. Do not simply stop taking the medication. For some infections you will be asked to return after a course of treatment to check that the infection has gone.

Do not have sex again until the time advised by the clinic. Depending on the infection, this may be for a certain length of time after treatment has finished or it may be until you are given the all clear from a repeat test. The aim is to prevent you from passing on the infection to others.

Advice from a sexual health adviser

Most clinics will have a sexual health adviser. You are likely to be seen by the adviser in addition to being seen by a doctor or nurse. A sexual health adviser is specially trained and can:

• Tell you more about STIs and how to avoid catching them in future. For example, the risk of infection increases with the number of changes of sexual partner. Wearing a condom during sex helps to prevent against STIs.

• Give you tips on how to cope with any current symptoms.

• Offer you free condoms which can help to prevent STIs.

• Give advice about what to tell your sexual partner or previous partners.

• Help you with contacting previous sexual partners who should be tested or treated. For example, you may be given a card with a number on it, plus a printed message advising the person who is given the card to visit the clinic and to bring the card along. This helps to match them with your notes.

Other services

In addition to diagnosing and treating STIs, if needed, a genitourinary medicine (GUM) clinic can also usually:

• Do a pregnancy test.

• Arrange counselling if you are pregnant and are not sure what to do.

• Arrange counselling about the decision to have an HIV test.

• Provide advice about contraception.

• Provide emergency contraception.

• Do a cervical smear test on women if one is due.

• Diagnose and treat some other conditions of the genitals that are not sexually transmitted. For example, a urine infection, thrush and some skin conditions affecting the genital area.

Although sex should be an enjoyable activity, it can put you at risk because it involves being very close (intimate) with another person, and so may allow infections to pass from one person to another. 'Safer sex' usually refers to having sex in a way which reduces your risks of catching an STI. Sex can never be completely without any risk but taking a few sensible precautions can reduce the risks greatly. See the leaflet on Safer Sex for more information.

Human papillomavirus (HPV) and hepatitis A and B vaccination

• Gay, bisexual and other men who have sex with men (MSM) are eligible for human papillomavirus (HPV), hepatitis A and hepatitis B vaccination.

• Some trans women (people who were assigned male at birth) and some trans men (people who were assigned female at birth) are also eligible for HPV, hepatitis A and hepatitis B vaccination.

• Ask the doctor or nurse at the specialist sexual health service clinic for more details.

See also the leaflets on HPV vaccine, Hepatitis A vaccine and Hepatitis B vaccine for further information.

Pre-exposure prophylaxis (PrEP) for HIV

PrEP is available for some people who are at high risk of HIV infection, such as if your sexual partner is HIV positive. PrEP is now available free on the NHS in England from sexual health clinics. PrEP may involve:

• Taking one tablet every day, or

• Only taking PrEP when needed (two tablets two to 24 hours before sex, one tablet 24 hours after sex and a further tablet 48 hours after sex). This is called event-based or on-demand PrEP.

PrEP is only for HIV prevention and does not protect against other STIs. Read our feature on Who should take HIV prevention drug PrEP?