Chlamydia is the most common STI in the UK and is caused by the bacterium Chlamydia trachomatis.

How is chlamydia transmitted?

Chlamydia is spread through contact with an infected person’s bodily fluids. This can happen during:

• Unprotected oral, vaginal, or anal sex
• Close genital contact (even if there’s no penetration, orgasm, or ejaculation)
• Sharing sex toys with an infected person

Gonorrhoea is the second most common STI in the UK and is caused by the bacterium Neisseria gonorrhoeae.

How is gonorrhoea transmitted?

Gonorrhoea is spread through contact with an infected person’s bodily fluids. This can happen during:

• Unprotected oral, vaginal, or anal sex
• Close genital contact (even if there’s no penetration, orgasm, or ejaculation)
• Sharing sex toys with an infected person

Trichomoniasis is an STI which is often present alongside other STIs and is caused by the parasite Trichomonas vaginalis.

How is trichomoniasis transmitted?

Trichomoniasis is spread through contact with an infected person’s bodily fluids. This can happen during:

• Unprotected vaginal sex
• Close genital contact (even if there’s no penetration, orgasm, or ejaculation)
• Sharing sex toys with an infected person

HIV is an STI that attacks the immune system and weakens your ability to fight off everyday infections.

How is HIV transmitted?

HIV can be spread through sexual and non-sexual means. HIV is spread through the exchange of bodily fluids with an infected person. This can happen during:

• Unprotected oral, vaginal, or anal sex
• Close genital contact (even if there’s no penetration, orgasm, or ejaculation)
• Biting or being bitten by an infected person
• Sharing toothbrushes, razors, or needles
• Sharing sex toys with an infected person

It has been established that people living with HIV who take antiretrovirals as prescribed and maintain an undetectable viral load have effectively no risk of sexually transmitting HIV to their partner(s).

Recent years have seen the development of pre-exposure prophylaxis (PrEP), an antiretroviral drug taken by people living without HIV to help protect them against infection. People living without HIV who take PrEP consistently and correctly reduce their risk of sexually contracting HIV to near-zero.

Currently some parts of the UK are trialling the free provision of PrEP, and we encourage you to consult with your NHS GUM clinic about its availability. This site may also provide helpful information with respect to obtaining PrEP.

Syphilis is an STI caused by the bacterium Treponema pallidum. There are 4 stages of syphilis: primary, secondary, latent, and tertiary. Without treatment, syphilis can progress through all 4 stages.

How is syphilis transmitted?

 Syphilis is spread primarily through contact with an infected lesion or sore. This can happen during:

• Unprotected oral, vaginal, or anal sex
• Close genital contact (even if there’s no penetration, orgasm, or ejaculation)
• Sharing sex toys with an infected person

Hepatitis B (HBV) is a virus that affects the liver and can cause acute (i.e. less than 6 months) or chronic (i.e. more than 6 months) infection.

How is HBV transmitted?

HBV is very contagious and can be spread through sexual and non-sexual means. HBV is spread through the exchange of bodily fluids with an infected person. This can happen during:

• Unprotected oral, vaginal, or anal sex
• Biting or being bitten by an infected person
• Sharing toothbrushes, razors, or needles
• Sharing sex toys with an infected person

HBV can live outside the body (in bodily fluids) for up to a week, and it is about 50 - 100 times more infectious than HIV.

The best way to prevent getting HBV is to get vaccinated. Since 2017, HBV vaccination has been part of the routine immunization schedule for all children in the UK, and is also available for adults in the UK who are considered “high risk.” Sometimes people need a “booster” to make sure the vaccine still provides sufficient immunity against HBV. Whether or not you need an HBV booster can be determined by a simple blood test. If you’re not sure whether or not you’ve had the HBV vaccine, or if you want to know if you need a booster, you should contact your GP or GUM clinic.

Hepatitis C (HCV) is a virus that affects the liver and can cause acute (i.e. less than 6 months) or chronic (i.e. more than 6 months) infection.

How is HCV transmitted?

HCV is extremely contagious and can be spread through sexual and non-sexual means. HCV is spread through contact with the blood of an infected person. For HCV to be transmitted, the blood from someone with HCV has to get into the bloodstream (e.g. via a cut or open wound) of someone else. Because HCV is transmitted via blood-to-blood contact, sexual activities that increase the potential for exposure to blood increase the risk of spreading HCV. This can happen during:

• Unprotected oral, vaginal, or anal sex
• Sex during menstration
• Biting or being bitten by an infected person
• Rough sex, group sex, or chem sex
• Having sex whilst being infected with another STI (e.g. herpes, gonorrhoea, or particularly HIV)
• Sharing toothbrushes, razors, clippers, scissors, or needles
• Sharing sex toys with an infected person

Hepatitis C is extremely contagious. HCV can live outside the body (in dried blood) for up to 6 weeks, and it is at least 10 times more infectious than HIV.

The best way to prevent spreading HCV is to remain aware and minimize any risk of blood-to-blood contact. With respect to sexual transmission, the best way to avoid spreading HCV is to use protection during any sexual activity. However, extra caution should be exercised as condoms and gloves can break.

Mycoplasma genitalium (MG) is an STI which is often present alongside other STIs, and is caused by the bacterium Mycobacterium genitalium.

How is MG transmitted?

MG is spread through contact with an infected person’s bodily fluids. This can happen during:

• Unprotected oral, vaginal, or anal sex
• Close genital contact (even if there’s no penetration, orgasm, or ejaculation)
• Sharing sex toys with an infected person

Most people with chlamydia--up to 70% of women, and 50% of men--have no symptoms, even though they can still pass the infection on to others. Those who develop symptoms usually do so within 1 - 3 weeks after exposure, though chlamydia symptoms can occur at any time, from days to months after infection. Symptoms of chlamydia can include:

• Pain in your lower abdomen
• Unusual vaginal bleeding (e.g. after sex, between periods)
• Unusual discharge from your vagina (e.g. more than usual) or penis (e.g. white, watery)
• Painful or swollen testicles
• Pain or burning when you pee
• Pain when you have sex
• Pain or discharge from your back passage (if you have a rectal chlamydia)
• Pain in your throat (if you have pharyngeal chlamydia, though usually this is asymptomatic)
• Pain or redness in your eye (if you have conjunctival chlamydia)

Many people with gonorrhoea--up to 50% of women and 10% of men--have no symptoms, even though they can still pass the infection on to others. Those who develop symptoms usually do so within the first 2 weeks after exposure (women usually develop symptoms in 2-10 days, and men in 2-5 days), though gonorrhoea symptoms can occur at any time, from days to months after infection. Symptoms of gonorrhoea can include:

• Pain in your lower abdomen
• Unusual vaginal bleeding (e.g. during sex, between periods, heavier periods)
• Unusual discharge from your vagina (e.g. more than usual, and which could be green or yellow) or penis (e.g. which could be white, yellow, or green)
• Painful or swollen testicles
• Pain or difficulty when you pee
• Pain when you have sex
• Itching or discharge (e.g. blood or mucus) from your back passage (if you have rectal gonorrhoea)
• Pain in your throat (if you have pharyngeal gonorrhoea, which is usually asymptomatic)
• Pain or redness in your eye (if you have conjunctival gonorrhoea)

Many people with trichomoniasis--up to 50% of women and 50% of men--have no symptoms, even though they can still pass the infection on to others. Those who develop symptoms usually do so within the first 4 weeks after exposure, though trichomoniasis symptoms can occur at any time, from days to months after infection. Symptoms of trichomoniasis can include:

• Pain in your lower abdomen
• Pain, itching, and/or redness around the vagina
• Unusual discharge from your vagina (e.g. often frothy and yellow, though it may be green, thin or thick, sometimes with an unpleasant smell) or penis (e.g. often thin and white)
• Pain, swelling, and/or redness around of the tip of your penis (glans)
• Pain when you pee, or peeing more often than usual
• Pain when you have sex
• Pain when you ejaculate

Some people with HIV have no symptoms and may not know they are infected, even though they can still pass the infection to others.

In the early stages of HIV infection, not all individuals develop symptoms. Those who do often present with a flu-like illness about 2 to 6 weeks after infection. After this time, HIV symptoms may not re-present until months or years later, although the virus is still actively destroying the immune system. Symptoms of HIV can include:

• Swollen lymph nodes
• Diarrhea
• Unintentional weight loss
• Recurrent infections
• Night sweats
• Skin rashes

Some people with syphilis have no symptoms, though they can still pass the infection on to others. Syphilis symptoms can occur at any time, from days to years after infection. The symptoms of syphilis depend on the stage, though all 4 stages of syphilis can be infectious.

Primary syphilis: the first symptoms often develop 2-3 weeks after initial infection.

• Small, painless ulcer at the site of infection (penis, vagina, anal area, mouth, lips, fingers), which may go unnoticed
• Swollen glands in the neck, armpits, or groin

Secondary syphilis: these symptoms develop within 6 months of infection, and can come and go for several months before disappearing.

• Blotchy red rash that can appear anywhere on the body, but is most often on the palms of the hands or the soles of the feet; these symptoms may disappear while the infection continues
• Small skin growths (like warts) on the vulva or around the anus
• White patches in the mouth
• Swollen glands in the neck, armpits, or groin
• Flu-like symptoms (i.e. fatigue, headaches, joint pains, fever)
• Patchy hair loss

Latent (hidden) syphilis: this period can be from 1 to 20 years after infection. During this time the person may have no symptoms, or they may have relapses of secondary syphilis symptoms

Tertiary (late) syphilis: this period can be anywhere from 1 to 45 years after infection, and can cause a variety of symptoms.

• Skin and bone lesions
• Cardiovascular problems, such as heart failure, heart murmurs, angina, aneurysms, or strokes
• Neurological problems, such as dementia, psychosis, lightning pains, numbness, loss of coordination, vision problems, or blindness

Many people with HBV have no symptoms and may not know they are infected, though they can still pass the infection on to others.

HBV symptoms can occur at any time, from weeks to years after infection. In the early stage of HBV infection, not all individuals develop symptoms. Those who do develop symptoms often experience a flu-like illness, including vomiting and diarrhoea, abdominal pain, or jaundice (yellowing of the skin/eyes) about 2-3 months after exposure. approximately 90% of adults are able to clear the HBV infection and have no ongoing health problems after about 3-6 months. During the acute stage of the HBV infection (i.e. the first 6 months), people are infectious and can spread the disease to others, whether or not they have symptoms. After the first 6 months, those who clear the acute HBV infection are usually immune for life.

However, approximately 10% of people with HBV go on to develop it chronically. People with chronic HBV are still infectious. Chronic HBV can cause severe liver damage (e.g. cirrhosis, liver failure, liver cancer).

Some people with HCV have no symptoms, while others may have vague symptoms (e.g. depression, skin problems, pain, digestive disorders), which can easily be attributed to other illnesses. Thus, many people with HCV may not realize they’re infected, even though they can still pass the infection to others, whether or not they have symptoms.

HCV symptoms can occur at any time, from weeks to years after infection. In the early (or acute) stage of HCV infection, most people (about 65%) do not develop symptoms. Those who do develop symptoms often experience a high fever (38° C or more), tiredness, loss of appetite, nausea and vomiting, abdominal pain, or jaundice (yellowing of the skin/eyes) a few weeks after exposure. Approximately 30% of people are able to clear acute HCV infection on their own and will have no further symptoms unless they become infected again. This means that people who clear HCV on their own do not become immune to future HCV infection.

During the acute stage of HCV infection (i.e. the first 6 months), people are infectious and can spread the disease to others, whether or not they have symptoms. However, approximately 55-85% of people with acute HCV do not clear the virus and remain infected with it for 6 months or more, meaning they go on to develop it chronically.

People with chronic HCV (i.e. more than 6 months) rarely clear the infection on their own. Because HCV stays in their body for many years, they can pass the virus to others. Chronic HCV can cause severe liver damage (e.g. cirrhosis, liver failure, liver cancer), and affect other areas of the body, including the digestive system, lymphatic system, immune system, and the brain.

Most people with MG--up to 75% of females, and 80% of males--have no symptoms, though they can still pass the infection on to others. Those who develop symptoms usually do so within 4 weeks of exposure, though MG symptoms can occur at any time, from days to years after infection. Symptoms of MG can include:

• Pain in your lower abdomen
• Unusual vaginal bleeding (e.g. if you have cervicitis; after sex, during sex, between periods)
• Unusual discharge from your vagina or penis (e.g. watery, cloudy)
• Painful or swollen testicles (if you have epididymo-orchitis)
• Pain or difficulty when you pee (if you have urethritis)
• Pain when you have sex
• Pain when you ejaculate
• Pain or discharge from your anus (if you have proctitis)

Don’t delay getting tested if you think you have chlamydia (i.e. you or your partner(s) have any of the above symptoms, a partner tells you they have an STI, or you had unprotected sex with someone new, etc). You can get tested for chlamydia at any time, though you may be advised to repeat the test 2 weeks after the date of any potential exposure, as chlamydia can take up to 2 weeks from the time of exposure to show up positive in tests. Unless you have symptoms, we recommend that you wait 2 weeks from the time of exposure to test for chlamydia.

Importantly, if you are pregnant or suspect you may be pregnant, and are concerned you may have chlamydia, you should not use an at-home test kit and should seek immediate attention and/or advice from a medical professional.

Don’t delay getting tested if you think you have gonorrhoea (e.g. you or your partner(s) have any of the above symptoms, your partner tells you they have an STI, or you had unprotected sex with someone new, etc). You can get tested for gonorrhoea at any time, though you may be advised to repeat the test 2 weeks after the date of potential exposure, as gonorrhoea can take up to 2 weeks from the time of exposure to show up positive in tests. Unless you have symptoms, we recommend that you wait 2 weeks from the time of exposure to test for gonorrhoea.

Importantly, if you are pregnant or suspect you may be pregnant, and are concerned you may have gonorrhoea, you should seek immediate attention and/or advice from a medical professional.

Don’t delay getting tested if you think you have trichomoniasis (i.e. you or your partner(s) have any of the above symptoms, your partner tells you they have an STI, or you had unprotected sex with someone new, etc). You can get tested for trichomoniasis at any time,though you may be advised to repeat the test 2 weeks after the date of potential exposure, as trichomoniasis can take up to 2 weeks from the time of exposure to show up positive in tests. Unless you have symptoms, we recommend that you wait 2 weeks from the time of exposure to test for trichomoniasis.

Trichomoniasis is often present alongside other STIs. If you test positive for trichomoniasis, we recommend that you and your recent sexual partner(s) are also tested for a range of other STIs, including chlamydia, gonorrhoea, syphilis, HIV, and hepatitis B.

Importantly, if you are pregnant or suspect you may be pregnant, and are concerned you may have trichomoniasis, you should seek immediate attention and/or advice from a medical professional.

Don’t delay getting tested if you think you have HIV (i.e. you or your partner have any of the above symptoms, your partner told you they have an STI, you had unprotected sex with a new partner, etc). You can get tested for HIV at any time, though HIV tests are most accurate 4 weeks after potential exposure. You may be advised to repeat the test 12 weeks after the date of potential exposure, as HIV can take up to 12 weeks from the time of exposure to show up positive in tests. We recommend that you wait 4 weeks from the time of exposure to test for HIV, with a repeat test at 12 weeks, though you don’t need to wait that long to seek support.

Importantly, if you are pregnant or suspect you may be pregnant, and are concerned you may have HIV, you should seek immediate attention and/or advice from a medical professional.

Don’t delay getting tested if you think you have syphilis (i.e. you or your partner have any of the above symptoms, your partner told you they have an STI, you had unprotected sex with a new partner, etc). You can get tested for syphilis at any time, though you may be advised to repeat the test 12 weeks after the date of potential exposure, as syphilis can take up to 12 weeks from the time of exposure to show up positive in tests. Unless you have symptoms, we recommend that you wait 12 weeks from the time of exposure to test for syphilis.

Importantly, if you are pregnant or suspect you may be pregnant, and are concerned you may have syphilis, you should seek immediate attention and/or advice from a medical professional.

Don’t delay getting tested if you think you have HBV (i.e. you or your partner have any of the above symptoms, your partner told you they have an STI, you had unprotected sex with a new partner, etc). You can get tested for HBV at any time, though HBV tests are most accurate 4 weeks after potential exposure. You may be advised to repeat the test 12 weeks after the date of potential exposure, as HBV can take up to 12 weeks from the time of exposure to show up positive in tests. We recommend that you wait 4 weeks from the time of exposure to test for HBV, with a repeat test at 12 weeks, though you don’t need to wait that long to seek support.

Importantly, if you are pregnant or suspect you may be pregnant, and are concerned you may have HBV, you should seek immediate attention and/or advice from a medical professional.

Don’t delay getting tested if you think you have HCV (i.e. you or your partner have any of the above symptoms, your partner told you they have an STI, you had unprotected sex with a new partner, etc). You can get tested for HCV at any time, though HCV tests are most accurate 4 weeks after potential exposure. You may be advised to repeat the test 12 weeks after the date of potential exposure, as HCV can take up to 12 weeks from the time of exposure to show up positive in tests. We recommend that you wait 4 weeks from the time of exposure to test for HCV, with a repeat test at 12 weeks, though you don’t need to wait that long to seek support.

Importantly, if you are pregnant or suspect you may be pregnant, and are concerned you may have HCV, you should seek immediate attention and/or advice from a medical professional.

Don’t delay getting tested if you think you have MG (i.e. you or your partner(s) have any of the above symptoms, a partner told you they have an STI, you had unprotected sex with someone new, etc.). You can get tested for MG at any time, though you may be advised to repeat the test 3 weeks after the date of potential exposure, as MG can take up to 3 weeks from the time of exposure to show up positive in tests. Unless you have symptoms, we recommend that you wait 3 weeks from the time of exposure to test for MG. 

Importantly, if you are pregnant or suspect you may be pregnant, and are concerned you may have MG, you should seek immediate attention and/or advice from a medical professional.