What Are the Most Common STIs in the UK (Stats & Trends)?

Introduction

Sexually transmitted infections remain a significant public health concern in the UK. Understanding which STIs are most common, who is most affected, and how trends are shifting can help individuals make informed decisions about their sexual health and testing needs.

This article provides a clear, factual overview of the most commonly diagnosed STIs in the UK, drawing on the latest available surveillance data from the UK Health Security Agency (UKHSA). It is written for informational purposes to support awareness and informed decision-making — it does not constitute medical advice.

Our clinic provides confidential STI testing services. We do not provide GP services, ongoing treatment, or prescriptions, but we can advise on appropriate next steps if further medical care is needed.

STI diagnoses in the UK have been rising in recent years, with chlamydia, gonorrhoea, and syphilis among the most commonly reported infections. Some groups — including young adults, men who have sex with men (MSM), and people of certain ethnic backgrounds — are disproportionately affected. Regular testing, particularly for those at higher risk, is one of the most effective ways to detect infections early and prevent onward transmission.

Key areas covered in this article:

• The most commonly diagnosed STIs in the UK
• Key statistics and trends
• Which groups are most affected
• Why many STIs go undiagnosed
• When testing may be appropriate
• How testing works

Statistics provide context, but individual risk depends on personal circumstances. Testing is the only reliable way to know your status.

Overview of STI Trends in the UK

The most recent data from the UK Health Security Agency (UKHSA) indicates that STI diagnoses have been broadly increasing, following a temporary dip during the COVID-19 pandemic when access to sexual health services was disrupted.

Key headline figures (based on most recent annual data):

• Approximately 392,000 new STI diagnoses were made in England in the most recent reporting year
• This represented an increase of approximately 24% compared to the previous year
• Chlamydia remained the most commonly diagnosed STI
• Gonorrhoea diagnoses increased significantly
• Syphilis diagnoses continued their upward trend
• Genital warts diagnoses continued to decline, likely reflecting the success of the HPV vaccination programme

These figures highlight that STIs remain prevalent across the UK population, and that several infections are becoming more common rather than less. Understanding how different infections are transmitted can help inform prevention decisions.

The Most Common STIs in the UK

1. Chlamydia

Chlamydia is consistently the most commonly diagnosed STI in the UK. It is a bacterial infection caused by *Chlamydia trachomatis* and is transmitted through vaginal, anal, or oral sex, as well as through sharing sex toys.

Key facts:

• Approximately 200,000+ diagnoses per year in England
• Most common in individuals aged 15 to 24
• Up to 70% of women and 50% of men with chlamydia have no symptoms
• Can cause complications including pelvic inflammatory disease (PID), infertility, and ectopic pregnancy if left untreated
• Easily treated with antibiotics

Because chlamydia is so frequently asymptomatic, many cases go undetected. Routine screening, particularly for young adults and those with new sexual partners, is widely recommended. A chlamydia test can detect the infection through a simple urine sample or swab. Many individuals carry the infection without being aware, which is why routine screening is recommended.

2. Gonorrhoea

Gonorrhoea is the second most commonly diagnosed bacterial STI in the UK. It is caused by *Neisseria gonorrhoeae* and can infect the genitals, rectum, and throat.

Key facts:

• Approximately 82,000+ diagnoses per year in England (most recent data)
• Diagnoses have increased by over 90% compared to pre-pandemic levels
• Particularly high rates among MSM and young adults
• Can be asymptomatic, particularly in women and in throat or rectal infections
• Antibiotic resistance is a growing concern with gonorrhoea

The significant rise in gonorrhoea cases is one of the most notable trends in UK sexual health. A gonorrhoea test can detect infection at multiple sites through urine samples or swabs.

3. Genital Warts (HPV)

Genital warts are caused by certain strains of human papillomavirus (HPV), most commonly types 6 and 11. Despite the overall decline in cases, they remain one of the most common STI-related conditions.

Key facts:

• Approximately 25,000 to 30,000 diagnoses per year in England
• Declining steadily due to the HPV vaccination programme
• Most common in young adults aged 20 to 24
• Diagnosed through visual clinical examination, not through blood or urine tests
• Treatment is available but the virus may persist

The decline in genital wart diagnoses is one of the most positive trends in UK sexual health and demonstrates the impact of the national vaccination programme.

4. Genital Herpes (HSV)

Genital herpes is caused by the herpes simplex virus, most commonly HSV-2, though HSV-1 (which also causes cold sores) can also cause genital infections.

Key facts:

• Approximately 35,000 to 40,000 diagnoses per year in England
• Many individuals carry the virus without knowing — the majority of genital herpes cases are thought to be undiagnosed
• The virus remains in the body for life and can cause recurrent outbreaks
• First episodes may involve painful blisters, but subsequent outbreaks are often milder
• Transmission can occur even when no visible symptoms are present (asymptomatic shedding)

A herpes test can help identify infection, though the timing and type of test used are important considerations.

5. Syphilis

Syphilis is caused by the bacterium *Treponema pallidum* and progresses through several stages if untreated. It has seen one of the most dramatic increases of any STI in the UK in recent years.

Key facts:

• Approximately 8,700+ diagnoses per year in England (most recent data)
• Diagnoses have increased by over 600% since the early 2000s
• Historically highest rates among MSM, though cases are increasing across all demographics
• Can be asymptomatic for extended periods (latent syphilis)
• Treatable with antibiotics, typically penicillin
• If untreated, can progress to serious complications affecting the heart, brain, and nervous system

A syphilis test is a straightforward blood test that can detect the infection at various stages. Find out more about latent syphilis and why it's hard to spot.

6. HIV

HIV (human immunodeficiency virus) attacks the immune system and, without treatment, can lead to AIDS. Significant advances in treatment mean that people living with HIV who are on effective antiretroviral therapy can achieve an undetectable viral load, meaning they cannot transmit the virus sexually.

Key facts:

• Approximately 3,000 to 4,000 new diagnoses per year in the UK
• An estimated 106,000 people are living with HIV in the UK
• Approximately 5% of those living with HIV are undiagnosed
• Available through rapid testing, laboratory blood tests, and self-testing kits
• PrEP (pre-exposure prophylaxis) has significantly reduced new infections in at-risk groups

HIV testing is an important component of comprehensive STI screening, particularly for those with ongoing risk factors.

7. Trichomoniasis

Trichomoniasis is caused by a parasite (*Trichomonas vaginalis*) and is less commonly diagnosed than bacterial STIs, partly because it is not always included in standard screening panels.

Key facts:

• Approximately 7,000+ diagnoses per year in England
• More commonly diagnosed in women
• Can cause discharge, irritation, and discomfort, but is often asymptomatic
• Easily treated with antibiotics
• May be underdiagnosed due to limited routine screening

8. Hepatitis B and C

Hepatitis B and hepatitis C are viral infections that affect the liver. While they can be transmitted through sexual contact, they are also spread through blood-to-blood contact, including sharing needles or from mother to child during birth.

Key facts:

• Hepatitis B and C are less commonly sexually transmitted than other STIs on this list
• Chronic hepatitis can lead to serious liver damage if untreated
• Hepatitis B vaccination is available and highly effective
• Hepatitis C is now curable with antiviral treatment
• Testing is recommended for individuals with potential exposure through sexual or blood-borne routes

Who Is Most Affected?

STI trends vary significantly across different demographic groups:

Age

• Young adults aged 15 to 24 account for a disproportionate share of STI diagnoses, particularly chlamydia and gonorrhoea
• STI rates generally decline with age, though syphilis and HIV diagnoses are spread across a wider age range

Gender and Sexual Orientation

• Men who have sex with men (MSM) are disproportionately affected by gonorrhoea, syphilis, and HIV
• Women are more likely to have asymptomatic infections, particularly chlamydia and gonorrhoea, leading to delayed diagnosis

Geography

• STI rates tend to be higher in urban areas, particularly London, which consistently reports the highest rates of diagnoses
• Access to testing services varies by region, which may affect diagnosis rates

Ethnicity

• Some ethnic groups experience higher rates of certain STIs, which may reflect broader social determinants of health, access to services, and other complex factors

These patterns highlight that whilst STIs can affect anyone who is sexually active, certain groups may benefit from more regular testing. For guidance on how often you should be tested, see our detailed article.

Why Do Many STIs Go Undiagnosed?

A significant proportion of STI infections remain undiagnosed. There are several reasons for this:

• Asymptomatic infections: Many STIs, including chlamydia, gonorrhoea, HPV, herpes, and syphilis, can be present without causing noticeable symptoms.
• Mild or non-specific symptoms: Some symptoms may be attributed to other causes, such as irritation, hormonal changes, or skin conditions.
• Testing gaps: Not all STI screens test for every infection. Individuals may believe they have been comprehensively tested when certain infections were not included.
• Stigma and reluctance: Concerns about judgement or embarrassment can prevent individuals from seeking testing.
• Lack of awareness: Some individuals may not realise they are at risk or may assume that monogamous relationships eliminate the possibility of infection.

These factors combine to mean that the true burden of STIs in the UK is almost certainly higher than official diagnosis figures suggest.

When Should You Consider STI Testing?

STI testing may be appropriate in a range of situations, including:

• You have had unprotected vaginal, anal, or oral sex
• You have a new sexual partner
• You or a partner have symptoms such as discharge, irritation, or skin changes
• A sexual partner has been diagnosed with an STI
• You have not been tested recently and have been sexually active
• You are concerned about potential exposure
• You are entering a new relationship and wish to know your status

Testing is a straightforward, confidential process. Our clinic offers a range of individual tests and comprehensive screening panels to suit different needs. A full STI screen can provide broad reassurance across multiple infections.

How Does STI Testing Work?

Testing methods vary depending on the infection being screened for:

• Urine tests: Commonly used for chlamydia and gonorrhoea screening. A simple urine sample is provided — no physical examination is required.
• Swab tests: Used for infections at specific sites (genital, throat, rectal). Self-swabbing is available for many tests.
• Blood tests: Used for HIV, syphilis, hepatitis B and C, and herpes. A small blood sample is taken and sent to an accredited laboratory.

Results are typically available within a few working days and are handled with complete confidentiality.

Frequently Asked Questions

What is the most common STI in the UK?

Chlamydia is consistently the most commonly diagnosed STI in the UK, with over 200,000 diagnoses per year in England alone.

Are STI rates increasing or decreasing in the UK?

Overall, STI diagnoses have been increasing in recent years, particularly for gonorrhoea and syphilis. Genital wart diagnoses have been declining due to the HPV vaccination programme.

Can you have an STI without symptoms?

Yes. Many STIs, including chlamydia, gonorrhoea, HPV, herpes, and syphilis, can be present without causing noticeable symptoms. Testing is the only reliable way to detect asymptomatic infections.

How often should I get tested?

This depends on your individual circumstances. Regular testing may be sensible if you have multiple partners, are in a new relationship, or have had unprotected sex. Annual testing is a reasonable baseline for sexually active individuals.

Does a standard STI test cover everything?

Not necessarily. Standard panels vary between providers. It is worth confirming which infections are included in any test you take. Some infections, such as HPV and mycoplasma, may not be included in basic screens.

Are young people more at risk of STIs?

Young adults aged 15 to 24 account for the highest proportion of chlamydia and gonorrhoea diagnoses. However, STIs can affect anyone who is sexually active, regardless of age.

When to Seek Medical Advice

Consider seeking professional advice if:

• You have symptoms such as unusual discharge, sores, irritation, or pain
• A sexual partner has been diagnosed with an STI
• You are concerned about a specific exposure
• You have not been tested recently and would like reassurance
• You are pregnant or planning a pregnancy

Our clinic can provide confidential STI testing and advise on appropriate next steps. If treatment or further clinical assessment is needed, we will guide you towards the appropriate service.

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Disclaimer: This article is for general informational purposes only and does not constitute medical advice, diagnosis, or treatment. The information provided is not a substitute for professional clinical judgement. Sexual health concerns should be assessed on an individual basis by a qualified healthcare professional. If you are experiencing persistent, severe, or worsening symptoms, please consult an appropriate healthcare service. Our clinic provides private STI testing services only — we do not prescribe medication, provide ongoing treatment, or offer GP services.

Written: 14 March 2026 | Next Review Due: 14 March 2027