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Sexually transmitted infections (STIs)


Expert reviewer, Dr Adrian Raby, General Practitioner
Next review due May 2018

Sexually transmitted infections (STIs) spread between people during sexual activity. You can catch an STI if you have unprotected vaginal, anal or oral sex, or share sex toys with someone who already has the infection.

STIs used to be called sexually transmitted diseases (STDs). Doctors now prefer the term STIs, because infections don't always have any symptoms, while diseases do.

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Common sexually transmitted infections

Chlamydia, genital warts, gonorrhoea and genital herpes are the most common STIs in the UK. You can learn more about these and other STIs, such as hepatitis B, HIV, pubic lice and syphilis below.

STIs are most common in people under 25, but anyone who’s sexually active can catch them.

If you think you have an STI, speak to your GP or visit a sexual health or genito-urinary medicine (GUM) clinic as soon as possible. Diagnosing and treating STIs early on in the infection may mean you’re less likely to have any complications.

Symptoms of sexually transmitted infections

STI symptoms vary from person to person. They also depend on which STI you have. You may not realise you have an STI, as the infections don’t always cause any symptoms. Sometimes an STI is only diagnosed when you’re having tests for something else, such as a urine or vaginal infection.

If you do have some STI symptoms, you may notice:

  • unusual discharge from your vagina, penis or anus – the discharge may be thicker than usual, coloured or smelly
  • stinging, pain or burning when you pass urine
  • itching, rashes, lumps, sores or blisters around your genitals (your vagina or penis) or anus
  • stinging, burning, pain and/or vaginal bleeding during or after sex
  • bleeding between your periods
  • pain or swelling of your testicles or epididymis (the tube that runs down the back of each testicle)
  • pain in your lower tummy area

Even if you don’t have any noticeable symptoms, you can still pass an STI to someone else. So, it's important to get yourself tested if you think you might be at risk of having an STI. This includes if you’ve had new sexual contact without using a condom or barrier contraceptive, or if you are planning to have unprotected sex. Some STIs can lead to more serious health problems, such as infertility, if they aren’t treated.

Diagnosis of sexually transmitted infections

If you think you might be at risk of having an STI, go to a sexual health or genito-urinary medicine (GUM) clinic. You don’t have to ask your GP to refer you to a GUM clinic – you can make your own appointment. If for any reason you can’t go to a sexual health clinic, call your GP for advice.

It’s best to go to a GUM clinic for a diagnosis, because the doctors and nurses there are specially trained to diagnose and treat STIs and have specialised equipment. They can also help to anonymously trace your previous sexual contacts, in case they need to be tested too.

All visits to a GUM clinic are confidential and you don't have to give your real name. You may be given a number to identify you instead. Your details won't be sent to your GP unless you confirm in advance that you’re happy for the clinic to do this.

Your doctor or nurse will usually ask about your medical history and whether you’ve had similar symptoms or an STI before. You may also be asked about your current and recent sexual partners, which types of sexual activities you practice, and which type of contraception you use.

Your doctor or nurse will usually need to examine you to look for any signs of infection. For women, this may involve an internal examination (looking at your vagina and cervix). Other tests for STIs include swabs (these are samples taken with a small, round cotton bud), and blood and urine tests.The tests shouldn’t hurt you, but you may feel uncomfortable if you have a swab or internal examination.

If you're diagnosed with an STI, it's important to contact your previous sexual partners so that they can be tested too. If they are affected they can then get treatment to avoid passing the infection on to other people. STIs often don’t cause any symptoms, so your previous sexual partners may not realise they have an infection. You may not want to contact them yourself. But GUM clinics can send anonymous notifications on your behalf if you're able to provide details.

Some GP practices also offer specialist sexual health services. It’s worth checking the website of your local GP practice.

You can buy home testing kits for some STIs, such as chlamydia, from pharmacies and websites. But not all testing kits are reliable or accurate, so it’s important to only buy them from trustworthy sources. If you’re under 25, you can take part in the National Chlamydia Screening Programme. For more information, see our FAQ: Are home testing kits available?

Causes of sexually transmitted infections

STIs are caused by bacteria, viruses or parasites. You can catch these infections during sex, genital contact, sharing sex toys and oral sex with an infected person.

People who use drugs can catch blood-borne viruses through sharing contaminated needles and injecting equipment. Some of these viruses are passed on during sexual contact, or contact with bodily fluids, as well.

Prevention of sexually transmitted infections

You can reduce your chances of catching an STI by taking certain precautions, such as practising safer sex. Safer sex methods include:

  • using condoms for vaginal, anal and oral sex.
  • getting tested for STIs before you have sex with a new partner, and suggest that they do this too
  • not sharing sex toys, and if you do share them make sure you wash them before and after anyone else uses them
  • getting vaccinated against certain STIs such as hepatitis B if you’re at risk (if you’re not sure ask your doctor or nurse)

The above can all help to reduce the risk of catching or passing on STIs.

Types of sexually transmitted infections

Chlamydia

Chlamydia is the most common bacterial STI in the UK. It’s particularly common in sexually active people under 25. The National Chlamydia Screening Programme recommends that all 15 to 24-year-olds in England should be tested every year if they’re sexually active. For more information, see the FAQ: Are home testing kits available?

Chlamydia infects your cervix (the neck of your uterus) or urethra (the tube that carries urine from your bladder and out through your penis or vulva). If the infection isn’t treated, it may spread to other parts of your body, such as your uterus and fallopian tubes.

Around seven in 10 women and half of men infected with chlamydia don’t have any signs or symptoms. When chlamydia does cause symptoms in women, these symptoms include:

  • bleeding between your periods
  • pain and/or bleeding during or after sex
  • pain in your lower tummy
  • a cloudy, yellow discharge from your vagina
  • pain when you pass urine
  • a high temperature

Possible symptoms in men include:

  • a white, cloudy or yellow-green discharge from your penis
  • pain when you pass urine
  • pain in your testicles

If you have a chlamydial infection in your rectum, you’re unlikely to have symptoms there. But sometimes you may notice some pain and an unusual discharge from your anus.

Chlamydia can be treated with antibiotics. If your doctor suspects you have chlamydia, they may start treating you before your test results are back. If chlamydia isn’t treated, it can lead to more serious problems, such as pelvic inflammatory disease and infertility in women.

Genital warts

Genital warts are the most common viral STI in the UK. They’re caused by the human papilloma virus (HPV). In the UK, all girls aged 12 and 13 are offered the HPV vaccine, as part of the National HPV Vaccination Programme. The vaccine used in the programme protects against the four types of HPV that cause cervical cancer. It also protects against some strains of the virus that cause genital warts.

Genital warts can appear on any part of your penis, vagina or anus. They may be small, smooth, round bumps, several larger bumps grouped together or small cauliflower-shaped bumps. The warts don’t always cause symptoms, but are sometimes painful, burning or itchy. It can take a few weeks or months after you first come into contact with the virus for the warts to appear.

Once you’ve been infected, you can pass the HPV virus to other people, even if you don’t have any genital warts at the time. Using a condom reduces your risk of passing on the virus but won’t fully protect you or your partner.

Genital warts often disappear on their own, so your doctor may suggest that you don’t treat them. You and your doctor will discuss the pros and cons of the different treatments and what’s right for you. The decision will depend on where your warts are, how much they’re affecting you and whether you have any other medical conditions.

If you decide to go ahead with the treatment, your doctor may suggest chemical products or liquid nitrogen freezing (cryotherapy). But there’s no guarantee that these treatments will work. After the treatment, the affected area may be red and sore for a while. You may need to have several treatments to get rid of the warts for good.

You may also be able to have the warts removed by laser treatment or surgery.

Genital herpes

Genital herpes is an STI caused by the herpes simplex viruses 1 and 2 (HSV-1 and HSV-2). Both these infections can cause cold sores around your mouth and genitals. Many people infected by these viruses don’t have any symptoms.

If you do have symptoms, you may first notice burning or tingling in your vagina, penis or anus. Later on, you may develop fluid-filled blisters or sores on the skin on or around your vagina, cervix or penis. If you’ve had oral sex, you may have sores around your mouth too. You may also feel generally unwell, tired or have a high temperature (fever). It may also be painful when you pass urine.

This first (primary) outbreak of genital herpes can last for up to four weeks if it isn’t treated. You may then have further outbreaks (flare-ups) in the following months, but these tend not to last as long or be as bad.

If you have genital herpes but don’t have any symptoms, you can still pass the virus on to your partner if your skin looks normal. Using condoms can reduce the chance of passing the virus on, but won’t protect your partner completely.Both the HSV-1 and HSV-2 viruses can affect your mouth and genitals.So, if you have either virus, you can pass it to your partner’s genitals or mouth during oral sex.

No treatment can completely remove the herpes simplex virus from your body. Once you catch the virus, you have it for life, but you should have fewer flare-ups as time goes on. For most people, the flare-ups do eventually stop completely.

When you have a flare-up, your doctor can prescribe antiviral medicines to help clear up your blisters more quickly. You may be able to ease any pain by having lukewarm baths and taking painkillers. If you have several attacks of genital herpes every year, your doctor may prescribe antiviral medicines that you take every day. These may prevent you having more attacks.

Gonorrhoea

Gonorrhoea is a common STI caused by bacteria that can infect your urethra, cervix, rectum, throat and eyes. Around one in 10 men and half of all women who are infected with gonorrhoea don’t have any symptoms. If you do get symptoms, it can take up to 14 days after you’re infected for them to appear.

In women, symptoms may include:

  • thin, slightly smelly vaginal discharge or more discharge than usual
  • pain when you pass urine
  • mild lower tummy pain or tenderness
  • bleeding between your periods

In men, symptoms may include:

  • thin yellow or green discharge from the tip of your penis
  • thin pain when you pass urine and needing to pass urine more regularly than usual
  • thin pain or tenderness in your epididymis (the tube that runs down the back of each testicle) – this is usually just on one side

If the infection is in your rectum, you won’t usually have any symptoms. But sometimes you may notice anal itching, bleeding or discharge. Gonorrhoea infection caused by oral sex can sometimes cause a sore throat. It’s important that you’re treated for gonorrhoea as soon as possible. If not, the infection can cause serious long-term health problems including pelvic inflammatory disease, infertility and some types of arthritis. Gonorrhoea can be treated with antibiotics.Don’t have unprotected sex until you’ve finished the treatment, your symptoms have cleared up completely, and your partner has been tested and treated.

Hepatitis B

Hepatitis B is an infection of your liver caused by the hepatitis B virus. It can be passed from one person to another through sexual contact. You can also catch hepatitis B from contaminated needles.

Up to seven in every 10 people with hepatitis B don’t have any symptoms. If the symptoms do appear, they can begin any time from six weeks to six months after you’ve been infected by the virus.

Hepatitis B symptoms can include:

  • feeling generally unwell, similar to having flu
  • losing weight
  • feeling sick or vomiting
  • aching in the top right of your tummy
  • yellowing of your skin and eyes (jaundice)
  • itchy skin
  • darker urine and lighter-coloured faeces

Although it can cause serious illness, most people with hepatitis B get better without any treatment. Your doctor will monitor you with regular blood tests. You can usually treat your symptoms by drinking lots of fluids, resting and taking anti-sickness medicines. Itching can be difficult to treat, but you may find simple measures help, such as wearing loose clothing and not having hot baths or showers.

If the infection hasn’t cleared from your body in six months, this is called chronic (long-term) hepatitis. You’re more likely to develop chronic hepatitis if you have a weak immune system. Many people with chronic hepatitis don’t have any symptoms, but they can still pass the infection on to other people.

If you have chronic hepatitis, you’ll be at a higher risk of developing cirrhosis of the liver and liver cancer. If you have cirrhosis of the liver, your normal liver tissue is replaced with scar tissue (called fibrosis). You’ll be referred to a doctor who specialises in the treatment of chronic hepatitis. You may be prescribed antiviral or other medicines that help your body to clear the infection.

If you’re at a high risk of catching hepatitis B, you can be vaccinated against the virus. People who are considered to be high risk include those who are HIV positive, men who have sex with men, health care workers, and travellers to certain countries. In the UK, all babies are now vaccinated against hepatitis B as part of the routine childhood immunisation programme.

If you think you’ve been exposed to hepatitis B and haven’t been vaccinated, go to a sexual health clinic as soon as possible. You can have an injection of the hepatitis B vaccine or, sometimes, a protective injection (hepatitis B immunoglobulin). This works best if you’re given it within 48 hours of being exposed to the hepatitis B virus.

HIV

Human immunodeficiency virus (HIV) is passed on from person to person as an STI. But it can also be passed on if people are in contact with infected blood, such as through contaminated needles or syringes.

HIV infection affects your immune system. Some people infected with HIV have no signs and symptoms at all. But you may develop flu-like symptoms up to six weeks after becoming infected. Your symptoms may include a high temperature, aches and pains, a sore throat, headaches and swollen glands. Over time, the HIV virus may weaken your immune system, putting you at risk of other infections and tumours.

Current treatments can’t get rid of HIV from your body completely, but they can control the virus and keep you healthy. You can take a combination of medicines called antiretrovirals to lower the levels of HIV in your blood, and improve your immune system. This can reduce your risk of developing serious health complications due to HIV and keep you well.

Some people may still pass on the infection through unprotected sex even if they’re taking antiretroviral medicines for HIV. So, it’s important to practise safe sex by always using a condom.

If you’ve had unprotected sex with someone who has HIV or is at high risk of HIV, visit a sexual health clinic or Accident and Emergency (A&E) department as soon as possible. You can take a course of antiretroviral medicines straightaway (called post-exposure prophylaxis) to reduce your risk of becoming infected. These medicines are more likely to work if you start taking them within 72 hours of exposure to HIV and take them for 28 days.

Pubic lice

Pubic lice can be passed on through close body contact. The lice are tiny insects that live in coarse body hair, such as pubic hair, chest hair, eyelashes and eyebrows. They’re not the same as head lice. They are sometimes called ‘crabs’.

The lice are very tiny and hard to see, but you may find them if you use a fine-toothed comb. You may notice itchy red spots on your skin or brown eggs (nits) stuck to your body hair. You may also see brown-black powdery spots in your underwear from the lice droppings. Pubic lice may make you feel itchy.

You can treat a pubic lice infection with insecticide lotions or shampoos. You need to use these over your whole body and leave them on for up to 12 hours. You may need to repeat the treatment seven days later.

Syphilis

Syphilis is a bacterial STI. It’s not as common in the UK as some other STIs, such as chlamydia and genital warts, but numbers are increasing. The disease has three stages: primary, secondary and tertiary.

The primary stage begins any time between nine and 90 days after you’re infected with the syphilis bacteria. You may have one or more sores on your skin. But because the sores are painless, you may not notice them. The sores can appear anywhere on your body, but will usually affect your penis, anus, vagina, cervix, mouth or lips. They usually heal within three to 12 weeks.

The secondary stage begins a few weeks after your sores have healed. You may feel generally unwell with flu-like symptoms and a rash.

If you’re not treated for syphilis, after a number of years you can develop the tertiary stage of the disease. This can cause serious health problems, affecting many parts of your body including your nervous system and heart.

Syphilis can be treated with antibiotics.

Frequently asked questions

  • If you’re under 25, you can get a free and confidential chlamydia test as part of the National Chlamydia Screening Programme. The tests are available from sexual health or genito-urinary medicine (GUM) clinics. You can do the test yourself and don’t need to be examined. You can also get the test at other places, including some pharmacies, as well as online, but make sure you buy it from a trustworthy source.

    You can buy HIV self-testing kits from high street shops and online. But not all HIV home testing kits are reliable or accurate, so only buy them from trustworthy sources too. Make sure you’re buying a legally approved HIV self-testing kit with a CE mark and that the packaging isn’t damaged and the seal isn’t broken.Follow the instructions carefully to make sure you’re using the test properly.

    STIs can have serious health implications. Ideally, you should use a testing kit with advice from a GP or other healthcare professional. So, if you’re worried about any STI or unusual symptoms, visit a GUM clinic or contact your GP. If you go to a sexual health or genito-urinary medicine (GUM) clinic, you don’t have to give your real name. The clinic won’t contact your GP unless you give them permission to do so.

  • If you think you have an STI and you’re pregnant, it’s important that you go to a sexual health or GUM clinic or contact your GP. You can pass some STIs on to your baby before, during or after the birth. You may need to be treated for the infection during pregnancy to protect you and your baby from serious health problems. Some STIs can mean your baby is born early or has a low birth weight. Sometimes, STIs can lead to a miscarriage late in pregnancy.

    Your treatment will depend on the specific infection and on how many weeks pregnant you are. This is because not all treatments are suitable during all stages of pregnancy. Most bacterial STIs can be treated with certain antibiotics that are safe to take during pregnancy. Viral STIs can be more difficult to treat, but there are ways to reduce the risk of passing the infection on to your baby.

    Your baby may need treatment when they’re born to help prevent complications of STIs. Sometimes, you may be offered a caesarean delivery to help prevent your baby becoming infected during the birth. HIV can be passed to babies through breastfeeding, so women in the UK who are HIV positive are recommended to use formula milk instead.

    Speak to your doctor or midwife about the best way to protect you and your baby if you’ve been diagnosed with an STI.

  • Yes, it’s a good idea to get tested. You don’t always have symptoms if you have a STI and if left untreated, it could lead to serious health complications.

    Sometimes you may not know that you have a STI because you don’t have any symptoms. But if you think you may have put yourself at risk of catching an infection (such as through unprotected sex or if you’ve had a new sexual partner), it's important to get tested. Go to a sexual health or genito-urinary medicine (GUM) clinic.

    If you do have an infection but don’t treat it, it may get worse. Your health and fertility can be affected, and you could also pass the STI on to someone else.

    Using a condom every time you have sex can reduce the risk of getting a STI. But not all STIs can be prevented in this way.

    If you would like further confidential advice, there are helplines you can ring to get more information. See our Other Helpful Websites section below.


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  • Reviewed by Graham Pembrey, Lead Editor, Bupa Health Content Team
    Expert reviewer, Dr Adrian Raby, General Practitioner
    Next review due May 2018



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