Sexually Transmitted Infections (STIs)

A sexually transmitted infection (STI) is an infection that can be passed from person to person when having sex. You can get an STI by having vaginal sex, anal sex, or oral sex. There are several different types of STI.

Key facts about sexually transmitted infections (STIs)

The WHO published these STI facts:

More than 1 million sexually transmitted infections (STIs) are acquired every day worldwide.
Each year, there are an estimated 376 million new infections with 1 of 4 STIs: chlamydia, gonorrhoea, syphilis and trichomoniasis.
More than 500 million people are estimated to have genital infection with herpes simplex virus (HSV).
More than 290 million women have a human papillomavirus (HPV) infection.
The majority of STIs have no symptoms or only mild symptoms that may not be recognized as an STI.
STIs such as HSV type 2 and syphilis can increase the risk of HIV acquisition.
988 000 pregnant women were infected with syphilis in 2016, resulting in over 350 000 adverse birth outcomes including 200 000 stillbirths and newborn deaths.
In some cases, STIs can have serious reproductive health consequences beyond the immediate impact of the infection itself (e.g., infertility or mother-to-child transmission)
The Gonococcal Antimicrobial Resistance Surveillance Programme has shown high rates of quinolone resistance, increasing azithromycin resistance and emerging resistance to extended-spectrum cephalosporins. Drug resistance, especially for gonorrhoea, is a major threat to reducing the impact of STIs worldwide.

Causes of sexually transmitted infections (STIs)

More than 30 different bacteria, viruses and parasites are known to be transmitted through sexual contact. Eight of these pathogens are linked to the greatest incidence of sexually transmitted disease. Of these 8 infections, 4 are currently curable: syphilis, gonorrhoea, chlamydia and trichomoniasis. The other 4 are viral infections which are incurable: hepatitis B, herpes simplex virus (HSV or herpes), HIV, and human papillomavirus (HPV). Symptoms or disease due to the incurable viral infections can be reduced or modified through treatment.

STIs are spread predominantly by sexual contact, including vaginal, anal and oral sex. Some STIs can also be spread through non-sexual means such as via blood or blood products. Many STIs—including syphilis, hepatitis B, HIV, chlamydia, gonorrhoea, herpes, and HPV—can also be transmitted from mother to child during pregnancy and childbirth.

A person can have an STI without having obvious symptoms of disease. Common symptoms of STIs include vaginal discharge, urethral discharge or burning in men, genital ulcers, and abdominal pain.

What are the main sexually transmitted infections (STIs)?

The most commonly diagnosed STI is chlamydia, which accounts for nearly half of all new STI diagnoses. First-episode genital warts account for about 1 in 7 of all new STI diagnoses, while gonorrhoea account for about 1 in 9 new diagnoses. Both syphilis and gonorrhoea diagnoses have increased, but the number of genital warts cases is falling in young women. This is largely because of the high coverage of the HPV vaccination programme for girls of school age in some countries.

The ten most common STIs are:

Chlamydia
Anogenital warts
Genital herpes
Gonorrhoea
Human immunodeficiency virus (HIV)
Hepatitis B
Hepatitis C
Pubic lice
Syphilis
Trichomonas

There are some other STIs that are uncommon - for example, donovanosis and chancroid.

Other conditions sometimes thought of as sexually transmitted infections (STIs)

Several other infections can affect the genital region, so may be mistaken for STIs. Although some of them can be passed on by sexual contact, they can all be caught in other ways. They include:

Scabies
Molluscum contagiosum
Urethritis
Balanitis
Pelvic inflammatory disease (PID)
Vulvitis
Thrush
Cystitis
Bacterial vaginosis

Scope of the problem

STIs have a profound impact on sexual and reproductive health worldwide.

More than 1 million STIs are acquired every day. In 2016, WHO estimated 376 million new infections with 1 of 4 STIs: chlamydia (127 million), gonorrhoea (87 million), syphilis (6.3 million) and trichomoniasis (156 million). More than 500 million people are living with genital HSV (herpes) infection and an estimated 300 million women have an HPV infection, the primary cause of cervical cancer. An estimated 240 million people are living with chronic hepatitis B globally. Both HPV and hepatitis B infections are preventable with vaccination.

STIs can have serious consequences beyond the immediate impact of the infection itself.

STIs like herpes and syphilis can increase the risk of HIV acquisition three-fold or more.
Mother-to-child transmission of STIs can result in stillbirth, neonatal death, low-birth-weight and prematurity, sepsis, pneumonia, neonatal conjunctivitis, and congenital deformities. Approximately 1 million pregnant women were estimated to have active syphilis in 2016, resulting in over 350 000 adverse birth outcomes of which 200 000 occurred as stillbirth or neonatal death.
HPV infection causes 570 000 cases of cervical cancer and over 300 000 cervical cancer deaths each year.
STIs such as gonorrhoea and chlamydia are major causes of pelvic inflammatory disease (PID) and infertility in women.

Prevention of sexually transmitted infections (STIs)

Counselling and behavioural approaches

Counselling and behavioural interventions offer primary prevention against STIs (including HIV), as well as against unintended pregnancies. These include:

comprehensive sexuality education, STI and HIV pre- and post-test counselling;
safer sex/risk-reduction counselling, condom promotion;
STI interventions targeted to key populations, such as sex workers, men who have sex with men (MSM) and people who inject drugs; and
STI prevention education and counselling tailored to the needs of adolescents.

In addition, counselling can improve people’s ability to recognize the symptoms of STIs and increase the likelihood they will seek care or encourage a sexual partner to do so. Unfortunately, lack of public awareness, lack of training of health workers, and long-standing, widespread stigma around STIs remain barriers to greater and more effective use of these interventions.

Barrier methods

When used correctly and consistently, condoms offer one of the most effective methods of protection against STIs, including HIV. Female condoms are effective and safe, but are not used as widely by national programmes as male condoms.

Range of reproductive health supplies: IUD, pills, condoms, emergency contraceptives IUD, implant and DMPA. Credit: Reproductive Health Supplies Coalition / Unsplash

Symptoms of sexually transmitted infections (STIs)

Symptoms of each STI can vary, from local symptoms affecting the genitals, to symptoms that affect various other parts of the body. The following is not a full list of all possible symptoms. However, these are the common symptoms to look out for:

A vaginal discharge.
Abnormal vaginal bleeding.
A discharge from the penis.
A sore, ulcer, rash, or lump that appears on the penis or around the vagina, vulva or back passage (anus).
Pain when you have sex.
Pain when you pass urine (although the common reason for this is a urine infection and not an STI).
Swelling of the glands in your groin.

But remember, in many cases of STI, no symptoms may develop. However, you can still pass on the infection to others even if you have no symptoms. Therefore, if you think that you may have an STI, it is best to get it checked out.

What should I do if I suspect that I have a sexually transmitted infection?

If you have a symptom that you think is due to an STI, or if you have no symptoms but are worried you have caught an STI then you should see your healthcare provider, or if it is available in your country you can visit a genitourinary medicine (GUM) clinic close to you. A GUM clinic is also called a Sexual Health clinic in some countries.

Until you are checked out by your healthcare provider or a GUM clinic or a Sexual Health clinic, and treated if necessary, you should not have sex. This is to prevent you passing on any infection.

Diagnosis of sexually transmitted infections (STIs)

Accurate diagnostic tests for STIs are widely used in high-income countries. These are especially useful for the diagnosis of asymptomatic infections. However, in low- and middle-income countries, diagnostic tests are largely unavailable. Where testing is available, it is often expensive and geographically inaccessible; and patients often need to wait a long time (or need to return) to receive results. As a result, follow up can be impeded and care or treatment can be incomplete.

The only inexpensive, rapid tests currently available for STIs are for syphilis and HIV. The rapid syphilis test is already in use in some resource-limited settings. A rapid dual HIV/syphilis test is not available whereby a person can be tested for HIV and syphilis from a single finger-stick and using a single testing cartridge. These tests are accurate, can provide results in 15 to 20 minutes, and are easy to use with minimal training. Rapid syphilis tests have been shown to increase the number of pregnant women tested for syphilis. However, increased efforts are still needed in most low- and middle-income countries to ensure that all pregnant women receive a syphilis test.

Several rapid tests for other STIs are under development and have the potential to improve STI diagnosis and treatment, especially in resource-limited settings.

Advice about sexual partners

If you are diagnosed with an STI then the clinic will encourage you to tell any current or recent sexual partners that you have an infection. You are not obliged to do this or to give out any information about other people. However, it is best that any recent sexual partners should know that they might also be infected. They should be offered testing and treatment if necessary, to prevent the infection being spread any further. This telling of sexual partners is sometimes called contact tracing. If you prefer, clinics can contact people anonymously if you do not wish to tell them yourself. You should be aware that recklessly exposing a sexual partner to the risk of infection is against the law.

Treatment of sexually transmitted infections (STIs)

The treatment that you will be offered depends on which STI is found. Effective treatment is currently available for several STIs.

Three bacterial STIs (chlamydia, gonorrhoea and syphilis) and one parasitic STI (trichomoniasis) are generally curable with existing, effective single-dose regimens of antibiotics.
A cream or lotion can clear pubic lice and scabies.
Topical treatments can usually clear most anogenital warts.
Treatments for genital herpes, hepatitis B, hepatitis C and HIV are more involved and complex. You will be given advice about what treatment options you have and given time to ask questions.
- For herpes and HIV, the most effective medications available are antivirals that can modulate the course of the disease, though they cannot cure the disease.
- For hepatitis B, antiviral medications can help to fight the virus and slow damage to the liver.

If you are prescribed antibiotics then it is important to finish the full course of tablets, or else the infection may not be fully cleared. If you develop side-effects then seek advice from your doctor, Sexual Health clinic or other healthcare provider as to what to do. Do not simply stop taking the medication. For some infections you will be asked to return after a course of treatment to check that the infection has gone.

Do not have sex again until the time advised by your doctor or clinic. Depending on the infection, this may be for a certain length of time after treatment has finished or it may be until you are given the all clear from a repeat test. The aim is to prevent you from passing on the infection to others.

Antimicrobial resistance (AMR) of STIs—in particular gonorrhoea—to antibiotics has increased rapidly in recent years and has reduced treatment options. Current Gonococcal AMR Surveillance Programme (GASP) have shown high rates of quinolone resistance, increasing azithromycin resistance and emerging resistance of extended-spectrum cephalosporins, last-line treatment. The emergence of decreased susceptibility of gonorrhoea to extended-spectrum cephalosporins together with AMR already shown to penicillins, sulphonamides, tetracyclines, quinolones and macrolides make gonorrhoea a multidrug-resistant organism. AMR for other STIs, though less common, also exists, making prevention and prompt treatment critical.

Advice from a sexual health adviser

Most GUM or Sexual Health clinics will have a sexual health adviser. You are likely to be seen by the adviser in addition to being seen by a doctor or nurse. A sexual health adviser is specially trained and can:

Tell you more about STIs and how to avoid catching them in future. For example, the risk of infection increases with the number of changes of sexual partner. Wearing a condom during sex helps to prevent against STIs.
Give you tips on how to cope with any current symptoms.
Offer you free condoms which can help to prevent STIs.
Give advice about what to tell your sexual partner or previous partners.
Help you with contacting previous sexual partners who should be tested or treated. For example, you may be given a card with a number on it, plus a printed message advising the person who is given the card to visit the clinic and to bring the card along. This helps to match them with your notes.

Other services

In addition to diagnosing and treating STIs, if needed, a Genitourinary Medicine (GUM) clinic can also usually:

Do a pregnancy test.
Arrange counselling if you are pregnant and are not sure what to do.
Arrange counselling about the decision to have an HIV test.
Provide advice about contraception.
Provide emergency contraception.
Do a cervical smear test on women if one is due.
Diagnose and treat some other conditions of the genitals that are not sexually transmitted. For example, a urine infection, thrush and some skin conditions affecting the genital area.

Sexually transmitted infection (STI) case management

Low- and middle-income countries rely on identifying consistent, easily recognizable signs and symptoms to guide treatment, without the use of laboratory tests. This is called syndromic management. This approach, which often relies on clinical algorithms, allows health workers to diagnose a specific infection on the basis of observed syndromes (e.g., vaginal discharge, urethral discharge, genital ulcers, abdominal pain).

Syndromic management is simple, assures rapid, same-day treatment, and avoids expensive or unavailable diagnostic tests for patients that present with symptoms. This approach results to overtreatment and missed treatment as majority of STIs are asymptomatic. Thus, in addition to syndromic management, screening strategies are essential.

To interrupt transmission of infection and prevent re-infection, treating sexual partners is an important component of STI case management.

Vaccines and other biomedical interventions

Safe and highly effective vaccines are available for 2 STIs: hepatitis B and HPV. These vaccines have represented major advances in STI prevention. The vaccine against hepatitis B is included in infant immunization programmes in 95% of countries and prevents millions of deaths from chronic liver disease and cancer annually.

As of October 2018, the HPV vaccine is available as part of routine immunization programmes in 85 countries, most of them high- and middle-income. HPV vaccination could prevent the deaths of millions of women over the next decade in low- and middle-income countries, where most cases of cervical cancer occur, if high (>80%) vaccination coverage of young women (ages 11-15) can be achieved.

Research to develop vaccines against herpes and HIV is advanced, with several vaccine candidates in early clinical development. Research into vaccines for chlamydia, gonorrhoea, syphilis and trichomoniasis is in earlier stages of development.

Other biomedical interventions to prevent some STIs include adult male circumcision and microbicides.

Male circumcision reduces the risk of heterosexually acquired HIV infection in men by approximately 60% and provides some protection against other STIs, such as herpes and HPV.
Tenofovir gel, when used as a vaginal microbicide, has had mixed results in terms of the ability to prevent HIV acquisition, but has shown some effectiveness against HSV-2.

Current efforts to contain the spread of STIs are not sufficient

Behaviour change is complex

Despite considerable efforts to identify simple interventions that can reduce risky sexual behaviour, behaviour change remains a complex challenge. Research has demonstrated the need to focus on carefully defined populations, consult extensively with the identified target populations, and involve them in design, implementation and evaluation.

Health services for screening and treatment of STIs remain weak

People seeking screening and treatment for STIs face numerous problems. These include limited resources, stigmatization, poor quality of services, and little or no follow-up of sexual partners.

In many countries, STI services are provided separately and not available in primary health care, family planning and other routine health services.
In many settings, services are often unable to provide screening for asymptomatic infections, lacking trained personnel, laboratory capacity and adequate supplies of appropriate medicines.
Marginalized populations with the highest rates of STIs—such as sex workers, men who have sex with men, people who inject drugs, prison inmates, mobile populations and adolescents—often do not have access to adequate health services.

Reference(s)
1). WHO: Sexually transmitted infections (STIs). Available online: https://www.who.int/news-room/fact-sheets/detail/sexually-transmitted-infections-(stis)
2). Patient: Sexually Transmitted Infections. Available online: https://patient.info/sexual-health/sexually-transmitted-infections-leaflet