Next Lesson - Pelvic Inflammatory Disease
Core
Infections of the reproductive tract are common in both men and women and have many different causes. Some of these infections can be sexually transmitted.
The sexually transmitted infections HIV and Hepatitis have their own dedicated articles in our Infection unit (see HIV and Hepatitis), and so will not be discussed in this article.
Sexually Transmitted Infections (STIs)
In England, the number of new STI diagnoses fell by 8.3% between 2024 and 2025 (source). Diagnosis rates remain relatively high in young people aged 15 to 24 years, in gay, bisexual and other men who have sex with men, and in people of some minority ethnic groups. STIs still place demand on primary care services, including GPs, and on sexual health services, including Genitourinary Medicine (GUM) clinics.
STIs are passed on by direct contact with an infected person. This includes contact between mucosal membranes (the moist lining of the genitals, mouth and anus) during vaginal, anal or oral sex. Some STIs, such as herpes, can also be passed on by skin-to-skin contact with the infected area. As a result sites of infection include the vagina, penis, anus or pharynx.
STIs are most commonly passed on through unprotected sex, which is the performance of sexual acts or sexual intercourse without a barrier method of contraception (e.g. a condom). Condoms (both external and internal) are the only form of contraception that both helps to prevent pregnancy and reduces the risk of STIs, but they do not give complete protection.
Risk Factors:
- Age - diagnosis rates remain relatively high in young people aged 15 to 24 years.
- Increased Number of Sexual Partners - more chances to come into contact with STIs.
- Lack of Education - individuals who are less well informed may be unaware of the risks of STIs or be unfamiliar with contraception.
- Excessive use of Alcohol or Recreational Drugs - alcohol and recreational drugs are known to impair judgement and lead to more high risk behaviours.
- Lack of Access to Contraception - in the UK, condoms are free from sexual health clinics and some GP surgeries, pharmacies and young people’s services, but some people are unable to access these.
- Geographic - the clinic might be inaccessible to the individual.
- Stigma - the individual might not want to be seen to attend the clinic due to the stigma sometimes attached to having an STI.
- Education - some people may not know that condoms are provided free.
In the UK, STIs can be managed and treated through a GUM clinic or another specialist sexual health service.
With all STIs, the patient should be advised to take part in a thorough screening programme, which checks for other infections. They should avoid all sexual contact (including oral sex) until they and their partners have finished treatment. For some infections they must wait a further 7 days after treatment (for example gonorrhoea, or chlamydia treated with azithromycin, an antibiotic). They should also take part in contact tracing.
As chlamydia and gonorrhoea are STIs that can be passed very easily between partners who are not using barrier contraception, any patient diagnosed should have their previous partners contacted. In the UK, the patient can tell their partners themselves, or a sexual health clinic may be able to contact them for the patient without giving the patient’s name (an anonymous service). At-risk parties are contacted, for example by text message, and advised to seek screening.
As seen in the table below, asymptomatic infections (infections without symptoms) require a longer period of contact tracing, because with asymptomatic infections, the origin is much harder to establish. The shorter periods in the table apply only to men with urethral symptoms (such as discharge or pain on passing urine). The longer periods apply to everyone else: all women, men with no symptoms, and anyone with symptoms at other sites (the rectum, throat or eye).
One of the difficulties with contact tracing stems from the fact that not all patients are willing or able to provide the contact information of their sexual partners. Patients may not have contact details for all of their past partners, and they cannot be forced to give up information they do not have.
Table - Period of contact tracing. In this table, ‘symptomatic’ means a man with urethral symptoms (such as discharge or pain on passing urine). Everyone else, including all women, follows the ‘asymptomatic’ row.
SimpleMed original by Dr. Maddie Swannack
Chlamydia infection is caused by the Chlamydia trachomatis, an obligate intracellular bacterium (meaning it must be inside the cell to replicate). It is classified as a Gram negative bacterium, although in practice it is difficult to Gram stain (a laboratory stain used to see bacteria under a microscope). Unlike most bacteria, its cell wall contains very little peptidoglycan (the strong mesh that gives most bacterial walls their rigidity). Chlamydia is the most commonly diagnosed STI in England (source).
Symptoms
Can be asymptomatic (without symptoms) in both sexes, but more likely to be asymptomatic in women.
Men - mild urethritis (inflammation of the urethra, the tube that carries urine out of the body), dysuria (pain on passing urine), and local inflammation such as epididymitis (inflammation of the epididymis, the coiled tube behind the testis) or prostatitis (inflammation of the prostate).
Women - vaginal discharge, dyspareunia (pain on vaginal penetration) or post-coital bleeding (bleeding after sex).
Complications
If untreated, chlamydia infection can progress to Pelvic Inflammatory Disease (PID) and infertility.
Chlamydia can also lead to complications outside of the genitals, such as reactive arthritis (joint inflammation triggered by an infection elsewhere in the body) and eye inflammation (conjunctivitis or uveitis, which is inflammation inside the eye that causes sore, red eyes sensitive to light). The classic triad of reactive arthritis is urethritis, conjunctivitis and arthritis. This can be remembered with the phrase ‘can’t pee, can’t see, can’t climb a tree’ (urethritis, conjunctivitis, arthritis respectively). Chlamydia is also an important differential diagnosis (a possible cause to consider) in a neonate (newborn baby) presenting with conjunctivitis. The bacteria can pass to the baby during vaginal birth from an infected mother.
Investigations
As Chlamydia trachomatis cannot be seen on Gram staining, Nucleic Acid Amplification Tests (NAAT, which detect the genetic material of the bacteria) are used to identify it.
The samples are obtained by a vulvovaginal swab (a swab of the vulva, the external female genitals, and the vagina) in women, and a urine sample in men. Extragenital sites (sites outside the genitals) including conjunctiva, pharynx and anus are swabbed if symptomatic or if other non vaginal sex has occurred.
Treatment
The current recommended treatment for chlamydia infection is doxycycline (an antibiotic) 100 mg twice daily for 7 days. It cannot be used in pregnancy or breastfeeding, and azithromycin (another antibiotic) is an alternative if doxycycline is unsuitable or not tolerated.
The current recommended treatment pathway can be found here.
Gonorrhoea infection is caused by the bacteria Neisseria gonorrhoeae, a Gram negative, intracellular diplococcus. This means that on Gram staining, it is seen inside the cell as pink circles, arranged in pairs.
Symptoms
Can be asymptomatic in both sexes, but more likely to be asymptomatic in women.
Men - discharge and dysuria.
Women - vaginal discharge and lower abdominal pain.
Due to the similar symptoms to chlamydia differentiation of cause is usually only achieved after NAAT.
Complications
If untreated, gonorrhoea infection can lead to PID, which occurs in up to 33% of women with gonorrhoea, and to epididymo-orchitis (inflammation of the testes and epididymis). Chlamydia can also cause PID, in up to 16% of women with untreated infection.
Investigations
While Neisseria gonorrhoeae does appear on Gram staining, the culturing required takes time. For this reason, NAAT is used, with vulvovaginal or endocervical (from the neck of the womb) swabs in women and a urine sample in men. A culture is still taken before treatment in people with a positive NAAT, to test which antibiotics the bacteria are sensitive to and to identify resistant strains.
Treatment
The treatment for gonorrhoea infection is a single 1 g intramuscular (IM) injection of ceftriaxone (an antibiotic). Other antibiotics are used if ceftriaxone cannot be used, for example because of an allergy. The MenB vaccine (a vaccine against meningococcal group B bacteria) can give some protection against gonorrhoea. It may be offered to men who have sex with men who are at higher risk of gonorrhoea.
The current recommended treatment pathway can be found here.
Syphilis infection is caused by the spirochete (spiral-shaped) Treponema pallidum bacterium. It has a characteristic four stage development if left untreated.
Primary Syphilis
This is the initial stage of a syphilis infection, presenting with a painless ulcer called a chancre at the site of sexual contact. Over the next few weeks, this ulcer will disappear, but during that time the patient is very infectious.
Secondary Syphilis
The secondary stage of a syphilis infection marks the dissemination (spread) of the bacteria around the body. It is characterised by systemic effects (effects on the whole body). A rash may appear on the body, with a fever, sores on the mucous membranes (the moist lining of the mouth and genitals), weight loss and general malaise (feeling unwell).
The patient is still very infectious at this stage. Secondary syphilis typically develops about 3 months after infection. It usually resolves on its own within 3 to 12 weeks, but without treatment the infection stays in the body.
Latent Syphilis
Following the secondary stage, the body pushes the disease into latency. At this point, the patient will have no symptoms, so latent syphilis is found by a blood test (serology, which detects antibodies) rather than by symptoms. Tests done for other reasons, such as antenatal screening (screening in pregnancy), sexual health screening or blood donation, may find it. If it is missed, it may only be found when a baby is born with congenital syphilis.
Tertiary Syphilis
This is the most severe stage of syphilis. It develops in about one third of untreated people, usually around 20 to 40 years after the initial infection, when the latent disease reactivates. Gummata can appear earlier, on average after about 15 years and sometimes within 2 years.
The symptoms of this stage of syphilis are severe:
- Gummata - large sores that occur on the skin or on the internal organs.
- Cardiovascular Effects - damage to the heart and blood vessels.
- Neurosyphilis - nervous system damage. It can occur at any stage of syphilis, not only in the tertiary stage.
Investigation
Syphilis can be diagnosed either through a blood test or a swab of the primary ulcer if the patient presents at this early stage.
Treatment
The treatment of syphilis is with benzathine benzylpenicillin, given as a single intramuscular dose in early syphilis (primary, secondary and early latent) and as three weekly doses in late latent, cardiovascular and gummatous syphilis. Neurosyphilis needs treatment that reaches the cerebrospinal fluid (the fluid around the brain and spinal cord), such as procaine penicillin with probenecid for 14 days.
The current recommended treatment pathway can be found here.
Anogenital warts (warts around the anus and genitals) are a very common viral STI, and are most often caused by Human papillomavirus (HPV) strains 6 and 11. The current vaccine used for HPV protects against these strains of HPV as well as HPV 16 and 18, which are the main causes of cervical cancer.
Anogenital warts typically present as painless warts on the penis or vulva (the external female genitals). They can also appear in the vagina, cervix (the neck of the womb) and perianal skin (the skin around the anus).
Treatment
There are many treatment options for the appearance of warts.
The first option is to leave them alone: anogenital warts are unsightly and infective, but they can safely be left untreated.
Topical creams and other treatments that the patient applies at home (for example podophyllotoxin and imiquimod) are also available to speed up healing. They cannot be used in pregnancy. If needed, more intense therapies such as cryotherapy (freezing them off) are possible. The choice depends on the type of wart and where the warts are.
However, getting rid of the warts will not get rid of the underlying infection, meaning that the warts can recur many times over a period of up to two years. After this time most people will have cleared the HPV infection, preventing recurrence unless reinfected.
The current recommended treatment pathway can be found here.
Herpes is a viral infection caused by the Herpes Simplex Virus (HSV). There are two types of this virus, HSV-1 and HSV-2. Traditionally HSV-1 is associated with oral ulcers and HSV-2 is associated with genital ulcers. However, it has since been shown that both of the virus types can cause both oral and genital ulcers.
Infection with any strain of HSV is especially dangerous in pregnancy, as it can cause neonatal herpes which can be fatal to the newborn child.
Symptoms
Commonly presents with painful ulcers, dysuria or discharge in both men and women. Can be asymptomatic.
It is transmissible in asymptomatic and symptomatic states, but is more infectious with ulceration.
Investigation
Genital herpes is often suspected from the history and examination (a clinical diagnosis). The diagnosis should be confirmed by taking a swab from an ulcer for viral PCR (polymerase chain reaction, a test that detects the genetic material of the virus), ideally in a specialist sexual health service. Serology (a blood test for antibodies) has a limited role and is not routinely used for acute diagnosis.
Treatment
Oral aciclovir (an antiviral drug) is the mainstay of treatment for genital herpes. However, herpes is impossible to cure. Aciclovir can reduce the length of ulceration (the time the ulcers last) in an attack. Daily suppressive antiviral treatment (taken every day to reduce attacks) can reduce the frequency of recurrences while treatment continues. Neither treatment eradicates latent HSV (virus that stays dormant in the body), so symptoms may come back after treatment stops. On average, people have 4 to 5 recurrences a year after a first symptomatic episode caused by HSV-2. HSV-2 recurs about four times as often as HSV-1. Recurrences usually become less severe and less frequent over time.
Lifestyle modifications might also aid in relieving the symptoms associated with the ulceration, such as using an emollient such as Vaseline, and avoiding sharing towels with other family members.
The current recommended treatment pathway can be found here.
A sexually transmitted protozoal infection (an infection with a single-celled parasite) caused by Trichomonas vaginalis.
Symptoms
Men - often asymptomatic but can cause dysuria or discharge.
Women - typically yellow vaginal discharge that irritates the vulva and vagina, has a foul smell and may be frothy in appearance.
Investigation
High vaginal swabs in women and urethral or penile-meatal swabs (a swab of the opening at the tip of the penis, often taken by the patient) in men are tested using nucleic acid amplification tests (NAATs, which detect the genetic material of the organism) for diagnosis. Urine samples can be used in men if the local NAAT allows it.
Treatment
Oral metronidazole is the treatment of choice for Trichomonas vaginalis.
The current recommended treatment pathway can be found here.
Other Infections of the Genitourinary Tract (Non-Sexually Transmitted Infections)
This section of the article is dedicated to infections of the reproductive tract that can be, but are not always, transmitted sexually.
Scabies and pubic lice are small parasites that cause irritation (itching) of the skin. Scabies is caused by a tiny mite that lays its eggs in the skin. Pubic lice are tiny insects that live on body hair, most often the pubic hair. Both can occur around the genital region, and scabies can affect any other region of skin. Both are spread mainly by close body contact, which is often sexual contact. Scabies can also spread through shared towels, clothes or bedsheets, especially in crusted scabies (a severe form with very large numbers of mites). Pubic lice rarely spread this way. The skin or hair is said to be infested rather than infected.
This vaginal infection is commonly caused by Gardnerella vaginalis but can be caused by many other anaerobic bacteria. It is caused by an imbalance in the normal flora of the vagina. Any practice that disrupts the vaginal flora and the normal pH of the vagina, including douching and washing inside the vagina, can cause the condition although the specific pathophysiology is unclear. Although not an STI itself it can increase the risk of contracting an STI.
Symptoms
Offensive smelling discharge that is often greyish in colour, but not associated with pruritus (itching) or pain.
Investigation
Diagnosis is usually clinical, supported by vaginal pH testing and/or microscopy. Routine culture is not recommended.
Treatment
Bacterial vaginosis without symptoms usually needs no treatment. For symptoms, oral metronidazole is the treatment of choice, as well as curtailing any risky practices such as douching.
The current recommended treatment pathway can be found here.
Vulvovaginal Candidiasis (Thrush)
This fungal infection of the vagina is commonly caused by Candida albicans and has multiple risk factors including immunosuppression (a weakened immune system, for example from HIV infection), pregnancy (higher oestrogen levels can lead to overgrowth of the fungus), diabetes (sugar in the urine encourages fungal growth), recent antibiotics (kill the local flora) and possibly the combined oral contraceptive pill (COCP), although evidence for this association is limited. Thrush can also present orally and is a common finding in elderly patients.
Symptoms
White, thick, non-offensive discharge associated with severe pruritus, pain and often dyspareunia.
Investigation
Investigation is not usually required in uncomplicated cases. High vaginal swabs may be considered if symptoms are recurrent, severe, or do not respond to treatment.
Treatment
Management of thrush can be tricky, especially if the precipitating risk factors cannot be treated. Thrush can often present as a recurring problem.
Treatment can be through creams, pessaries (tablets placed in the vagina) or oral antifungals (medicines that kill fungi) of the -azole class like the oral treatment fluconazole. Oral fluconazole must not be used in pregnancy. A vaginal clotrimazole pessary is used instead.
The current recommended treatment pathway can be found here.
Vaginal discharge is a common initial presentation of many of these diseases. It is therefore important to understand the different types of vaginal discharge as this will assist in achieving a diagnosis.
Vaginal discharge is normal, and it is normal for it to vary slightly in texture or amount throughout the menstrual cycle. It is important to emphasise that it is the change from normal for that patient that is a cause for concern.
Table - The characteristics of vaginal discharge and the possible conditions associated with that presentation
SimpleMed original by Dr. Maddie Swannack
While the above table can be helpful in practice, it is also important to include the rest of the clinical picture when making a diagnosis.
Guidance is revised from time to time, so check the current version of the treatment pathways on the website https://cks.nice.org.uk/ before relying on any treatment in this article.
Edited by: Dr. Ben Appleby
Reviewed by: Dr. Thomas Burnell and Dr. Marcus Judge
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