Sexually transmitted infections affect people of all ages and backgrounds across the UK. Public health surveillance data consistently shows ongoing transmission of several common infections, with some rates increasing in recent years. Understanding which infections are most prevalent, how they present, and how they are detected is an important part of managing sexual health.
Many STIs are manageable when detected early, but symptoms alone are an unreliable indicator of infection status. Some infections produce no symptoms at all, while others cause signs that overlap with unrelated conditions. This means that laboratory testing remains the only reliable method for confirming whether an infection is present.
This article provides an overview of the most common STIs in the UK, explains the difference between bacterial and viral infections, and outlines how symptoms may vary between men and women.
Quick Answer: What Are the Most Common STIs in the UK?
The most common sexually transmitted infections in the UK include chlamydia, gonorrhoea, genital herpes, syphilis and human papillomavirus (HPV). Many infections are asymptomatic, particularly in early stages. Symptoms vary between men and women, and some STIs may remain undetected without laboratory screening.
Key Points:
- •Chlamydia remains one of the most frequently diagnosed STIs
- •Gonorrhoea rates have increased in recent years
- •Viral STIs such as herpes and HPV are common
- •Many infections cause mild or no symptoms
- •Laboratory testing confirms infection
Laboratory testing is required to confirm any infection.
Understanding Bacterial vs Viral STIs
Sexually transmitted infections are caused by different types of pathogens, and understanding the distinction between them is helpful for interpreting test results and understanding management options.
- •Bacterial STIs: These include chlamydia, gonorrhoea, and syphilis. They are caused by bacterial organisms and are typically identified through urine samples, swabs, or blood tests
- •Viral STIs: These include genital herpes (HSV), human papillomavirus (HPV), and HIV. They are caused by viruses and may require blood tests or swabs for detection
- •Parasitic infections: Trichomoniasis is caused by a parasite and can be detected through laboratory analysis of swabs or urine samples
Regardless of the type of pathogen involved, all sexually transmitted infections require laboratory confirmation. Symptom overlap between different infections is common, which means that clinical testing is essential for accurate identification.
Chlamydia: The Most Frequently Reported STI
Chlamydia is one of the most frequently diagnosed sexually transmitted infections in the UK. It is a bacterial infection caused by Chlamydia trachomatis and is often detected through routine screening rather than symptom-driven testing, because a significant proportion of infections produce no noticeable symptoms.
When symptoms do occur, they may include:
- •Unusual discharge from the genitals
- •Pain or discomfort during urination
- •Pelvic discomfort in women
- •Testicular discomfort in men
Chlamydia symptoms in men may include urethral discharge and discomfort during urination, though many men carry the infection without any signs at all. In women, the infection frequently remains asymptomatic, which is why routine screening is considered particularly important.
A chlamydia and gonorrhoea test can detect both infections from a single sample, providing a practical approach to screening.
We provide laboratory-based STI screening. Treatment arrangements are managed separately if required.
Gonorrhoea: Rising Rates in the UK
Gonorrhoea is a bacterial infection caused by Neisseria gonorrhoeae. UK surveillance data has shown increasing rates of gonorrhoea diagnoses in recent years, making it one of the more prevalent sexually transmitted infections currently reported.
Symptoms of gonorrhoea, when present, may include:
- •Yellow or green discharge from the genitals
- •Painful or uncomfortable urination
- •Rectal discomfort or discharge if infection is at the rectal site
- •Sore throat if pharyngeal infection is present
Gonorrhoea signs in women may be mild or absent entirely. Women may experience changes in vaginal discharge or mild pelvic discomfort, but these symptoms are easily attributed to other causes. In men, urethral discharge and painful urination are more commonly reported, though asymptomatic cases still occur.
Gonorrhoea can infect the throat, rectum, and genitals, and multi-site testing may be appropriate depending on sexual practices and exposure history.
Genital Herpes (HSV-1 and HSV-2)
Genital herpes is a viral infection caused by herpes simplex virus type 1 (HSV-1) or type 2 (HSV-2). It is one of the more common viral STIs in the UK and is transmitted through direct skin-to-skin contact with an infected area.
When symptoms occur, they may include small blisters or sores around the genital or rectal area. These may be accompanied by localised tingling, itching, or discomfort. Initial outbreaks tend to be more noticeable, while subsequent episodes may be milder.
An important characteristic of herpes is asymptomatic viral shedding. This means the virus can be present on the skin surface and potentially transmissible even when no visible sores or symptoms are present. Many individuals who carry the virus are unaware of their infection status.
Laboratory testing, including swab tests of active lesions or blood tests for antibodies, can help confirm herpes infection.
Syphilis: A Re-emerging Infection
Syphilis is a bacterial infection caused by Treponema pallidum. After a period of declining rates, syphilis diagnoses have been increasing in the UK, particularly in certain demographic groups. It is transmitted through direct contact with a syphilis sore during vaginal, anal, or oral sex.
Syphilis progresses through recognised stages:
- •Primary stage: A painless sore (chancre) appears at the site of infection. It may go unnoticed, particularly if located internally
- •Secondary stage: A skin rash may develop, sometimes accompanied by other non-specific symptoms. This stage may also resolve without intervention
- •Latent phase: The infection enters a dormant period during which no symptoms are present but the bacterium remains in the body. This phase can last for an extended period
Early detection through blood testing is important because syphilis is identifiable at each stage through laboratory analysis. The infection may progress through stages if not identified, which is why screening is a relevant consideration for sexually active individuals.
HPV: Extremely Common but Often Silent
Human papillomavirus (HPV) is one of the most widespread sexually transmitted infections globally. There are many strains of HPV, and most people will encounter at least one strain during their lifetime. The majority of HPV infections resolve naturally without causing any health issues.
Many strains of HPV produce no symptoms at all, meaning individuals may carry and transmit the virus without being aware. Some strains are associated with genital warts, which present as small growths or bumps in the genital or anal area. Other strains, classified as high-risk, are associated with cellular changes that may be identified through cervical screening programmes.
HPV vaccination programmes in the UK have been introduced to reduce the prevalence of certain high-risk strains. However, vaccination does not cover all strains, and laboratory-based screening remains relevant for monitoring sexual health status.
HIV: Less Common but Important to Screen For
Human immunodeficiency virus (HIV) affects the immune system and, while less frequently diagnosed than some other STIs in the UK, remains an important infection to screen for. HIV is transmitted through specific bodily fluids and can be present without producing recognisable symptoms for an extended period.
In the initial weeks following exposure, some individuals experience a short flu-like illness known as seroconversion. Symptoms may include fever, fatigue, sore throat, and swollen lymph nodes. However, these signs are non-specific and easily attributed to other causes.
After the initial phase, HIV may enter a prolonged asymptomatic period during which the individual feels well but the virus remains active in the body. Blood testing is required to confirm HIV status, and early detection supports informed health management.
HIV testing is typically included as part of a comprehensive sexual health screen and involves a blood sample analysed for antibodies, antigens, or viral RNA.
Why Many STIs Show No Symptoms
A significant proportion of sexually transmitted infections are asymptomatic, meaning they produce no noticeable signs. This is one of the primary reasons why STIs continue to be transmitted within the population — individuals who feel well may not seek testing and may unknowingly pass infections to partners.
Several factors contribute to the absence of symptoms:
- •Asymptomatic transmission: Bacteria and viruses can be present in bodily fluids and on skin surfaces without causing recognisable signs, allowing transmission during sexual contact
- •Mild symptoms overlooked: Some infections produce only subtle signs such as slight discharge changes or minor discomfort, which may be dismissed as normal variation
- •Overlap with other conditions: STI symptoms can resemble those of urinary tract infections, skin irritation, or other common conditions, leading to misattribution
- •Laboratory screening importance: Because symptoms are unreliable, routine laboratory screening is the most effective way to identify infections and confirm sexual health status
When Should You Consider STI Testing?
STI testing does not require the presence of symptoms. There are several circumstances in which screening may be a relevant consideration:
- •New sexual partner: Testing before or shortly after beginning a new sexual relationship provides baseline information about infection status
- •Unprotected intercourse: Any sexual contact without barrier protection increases the possibility of STI exposure, making testing a practical step
- •Routine sexual health screening: Periodic testing at regular intervals supports ongoing awareness of infection status, regardless of symptom presence
- •If symptoms appear: Any new or unusual symptoms in the genital, rectal, or oral area may warrant laboratory investigation
A comprehensive STI screening panel can test for multiple infections from a single visit, providing a thorough assessment of sexual health status.
We provide laboratory-based STI screening. Treatment arrangements are managed separately if required.
People Also Ask
What is the most common STI in the UK?
Chlamydia remains one of the most frequently reported sexually transmitted infections in the UK. It is commonly identified through routine screening programmes and private testing services. The infection often presents without noticeable symptoms, which is why laboratory screening is considered particularly important for early detection.
Do men and women have different STI symptoms?
Yes. Symptoms of many sexually transmitted infections may present differently depending on sex. Some infections are more likely to be asymptomatic in women than in men, while others may produce distinct symptoms at different anatomical sites. Laboratory testing is recommended regardless of symptom presentation, as absence of symptoms does not exclude infection.
Are viral STIs more common than bacterial ones?
Both viral and bacterial STIs are common in the UK. Prevalence varies depending on age group, geographic location, and sexual activity patterns. Bacterial infections like chlamydia and gonorrhoea are frequently diagnosed, while viral infections such as HPV and herpes are widespread across the population. Comprehensive screening can identify both types.
Can you have an STI without knowing?
Yes. A significant proportion of sexually transmitted infections do not cause noticeable symptoms, particularly during the early stages. Infections such as chlamydia, gonorrhoea, HIV, and syphilis can all be present without producing recognisable signs. Routine laboratory screening is the only reliable way to confirm infection status.
How often should you test for STIs?
Testing frequency depends on individual risk profile and sexual activity. Screening may be appropriate when starting a new relationship, after unprotected intercourse, or at regular intervals for sexually active individuals. There is no single schedule that applies to everyone, and frequency should reflect personal circumstances.
This article is for general information. Laboratory testing is required to confirm any infection.
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For general information only — not a substitute for professional advice. In an emergency call 999, visit A&E, or call NHS 111.