Types of sexually transmitted infections

Key Facts

Every day, more than 1 million cases of sexually transmitted infections occur worldwide, and the majority of these cases are without disease.
It is estimated that there are 374 million new infections annually with one of the following four types of sexually transmitted infections, chlamydia, gonorrhea, syphilis and trichomoniasis.
It is estimated that more than 500 million people between the ages of 15 and 49 are infected with the genital herpes simplex virus (1).
In 2018, HPV infection was associated with 570,000 cases of cervical cancer, and more than 311,000 deaths from cervical cancer each year (2).

It is estimated that approximately 1 million pregnant women were infected with syphilis in 2016, resulting in more than 350,000 negative birth outcomes, including 200,000 stillbirths and neonatal deaths (3).

STIs directly affect sexual and reproductive health through stigma, infertility, cancers and pregnancy complications, and can increase the risk of HIV infection.
Drug resistance, especially for gonorrhea, is a major factor threatening to reduce the burden of sexually transmitted infections worldwide.


There are more than 30 different types of bacteria, viruses, and parasites that are known to be sexually transmitted. Eight of these pathogens are associated with the highest rates of sexually transmitted diseases. Of these causes, 4 cases can be cured at the present time: syphilis, gonorrhea, chlamydia and trichomoniasis. The other four cases are viral infections that cannot be cured: hepatitis B virus, herpes simplex virus (or herpes), human immunodeficiency virus (HIV) and human papillomavirus.

The predominant way sexually transmitted infections are spread is through sexual contact, including vaginal, anal and oral sex. Some types of sexually transmitted infections may be passed from mother to child during pregnancy, childbirth, and breastfeeding.

A person may have a sexually transmitted infection without showing obvious symptoms. Common symptoms of sexually transmitted diseases include vaginal discharge, urethral discharge or burning in men, genital sores, and abdominal pain.

Scope of the problem

Sexually transmitted infections profoundly affect sexual and reproductive health worldwide.

More than 1 million sexually transmitted infections occur every day. In 2020, WHO estimates that there will be 374 million new infections with one of the four types of sexually transmitted infections: chlamydia (129 million cases), gonorrhea (82 million cases), syphilis (7.1 million cases) and trichomoniasis (156 million cases). It is estimated that more than 490 million people were living with herpes simplex virus (HSV) infection in 2016, and an estimated 300 million women were infected with HPV, the leading cause of cervical cancer. It is also estimated that 240 million people live with chronic hepatitis B virus globally. Both HPV and hepatitis B can be prevented through vaccination.

Sexually transmitted infections can have serious consequences that go beyond the direct effect of the infection itself.

Sexually transmitted infections, such as herpes, gonorrhea and syphilis, can increase the risk of HIV infection.

Transmission of sexually transmitted infections from mother to child can lead to stillbirth, neonatal death, low birth weight, prematurity, sepsis, pneumonia, neonatal conjunctivitis, and congenital malformations. It is estimated that approximately 1 million pregnant women contracted active syphilis, resulting in more than 350,000 negative birth outcomes, including 200,000 stillbirths or neonatal deaths.

HPV leads to cervical cancer, the fourth most common type of cancer among women globally, and is estimated to have caused 570,000 new infections in 2018, and more than 311,000 deaths annually (2).

Hepatitis B caused an estimated 820,000 deaths in 2019, with the majority of these deaths due to cirrhosis and hepatocellular carcinoma (i.e. primary liver cancer).
Sexually transmitted infections, such as gonorrhea and chlamydia, are major causes of pelvic inflammatory disease and infertility in women.

Prevention of sexually transmitted infections

Condoms, when used properly and consistently, offer one of the most effective means of preventing sexually transmitted infections, including HIV. Condoms also protect against unintended pregnancy in consensual sexual relations. Although condoms are effective, they do not provide protection against sexually transmitted infections that cause ulcers outside the genitals (ie syphilis or genital herpes). Whenever possible, condoms should be used for all vaginal and anal sex.

Safe and highly effective vaccines are available for two types of sexually transmitted infections, hepatitis B and human papillomavirus. These vaccines represent a significant advance in the prevention of sexually transmitted infections. By the end of 2020, the HPV vaccine was included as part of routine immunization programs in 111 countries, mostly high- and middle-income countries. Vaccination against HPV could prevent the deaths of millions of women over the next decade in low-income and low-income countries

Middle income, where most cases of cervical cancer occur, provided that vaccination coverage is high (more than 80%) among young women (aged 11-15 years).

Research into the development of herpes and HIV vaccines is progressing, as we are witnessing the early clinical development of several experimental vaccines. There is increasing evidence that the meningitis (MemB) vaccine has cross-protection against gonorrhea. More research is needed on chlamydial, gonorrhea, syphilis and trichomoniasis vaccines.

Other biological and medical interventions to prevent some types of sexually transmitted infections include adult male circumcision and germicides.

Diagnosis of sexually transmitted infections

Accurate tests to diagnose sexually transmitted infections are widely used in high-income countries. These tests are especially useful for diagnosing asymptomatic infections. But diagnostic tests in low- and middle-income countries are largely unavailable. Where these tests are available, they are often expensive and inaccessible geographically, and patients often need to wait a long time (or have to return) for results. As a result, follow-up may be hampered or care or treatment may not be completed.

The only rapid and inexpensive tests currently available for sexually transmitted infections are those for syphilis, hepatitis B, and HIV. The rapid syphilis test is already used in some resource-constrained settings. A dual rapid test for HIV and syphilis is now available, whereby a person can be tested for HIV and syphilis with a single finger slide and a single test cartridge. These tests are accurate, can give results within 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 who are tested for syphilis. However, increased efforts are still needed in most low- and middle-income countries to ensure that all pregnant women are tested for syphilis at their first antenatal care visit.

Several rapid tests for other sexually transmitted infections are in development and have the potential to improve the diagnosis and treatment of these infections, especially in resource-constrained contexts.

Treating sexually transmitted infections

There is currently a cure for many types of sexually transmitted infections.

Three types of sexually transmitted bacterial infections (chlamydia, gonorrhea and syphilis) and one parasitic type of sexually transmitted infection (trichomoniasis) can generally be treated with existing, effective regimens with a single dose of antibiotics.
With regard to herpes and HIV, the most effective treatments available are antivirals that can modify the course of the disease, although they are unable to cure it.
For the hepatitis B virus, antiviral treatments can help fight the virus and slow the rate of liver damage.

Antimicrobial resistance of sexually transmitted infections – especially gonorrhea – has increased rapidly in recent years, and has limited treatment options. The surveillance program for gonococcal resistance showed high rates of antibiotic resistance, including quinolone drugs, increased resistance to azithromycin, and emerging resistance to broad-spectrum cephalosporins, a “last-stage” treatment, increasing the risk of untreatable gonorrhea. (4)

Antimicrobial resistance is also found in other, although less common, sexually transmitted infections, underlining the critical importance of prevention and prompt treatment.

Management of sexually transmitted infections

Low- and middle-income countries rely on the identification of persistent, easily identifiable signs and symptoms to guide treatment, without the use of laboratory tests. This is called syndromic management. This approach, which is often based on clinical computational methods, allows health workers to diagnose a specific infection on the basis of observed symptoms (eg vaginal discharge, urethral discharge, genital ulcers or abdominal pain).

Syndrome management is easy, ensures rapid same-day treatment, and avoids the need for expensive or unavailable diagnostic tests for symptomatic patients. This approach results in over-treatment and under-treatment, since the majority of infections are asymptomatic. Therefore, WHO recommends that countries strengthen management of the syndromes by gradually incorporating laboratory tests to support diagnosis. In environments where quality-assured molecular assays are available, treatment of sexually transmitted infections based on laboratory testing is recommended. Furthermore, STI screening strategies are necessary for those at higher risk, such as sex workers, men who have sex with men, adolescents in some settings, and pregnant women because of the potentially severe consequences for children.

An important component of the management of sexually transmitted infections is the treatment of sexual partners in order to stop the infection and prevent its recurrence.
spread control

Behavior change is a complex challenge

Despite tremendous efforts to identify simple interventions that can reduce risky sexual behaviors, behavior change remains a complex challenge. Research has shown the need to focus on population groups

Carefully defined intent, extensive consultation with the specific target population, and their involvement in the design, implementation and evaluation processes.

Education and counseling can improve people’s ability to recognize symptoms of sexually transmitted infections, increase the likelihood that they will seek care, and encourage a sexual partner to do so. Unfortunately, the lack of public awareness, the lack of training among health workers, and the long-standing and widespread stigma around sexually transmitted diseases continue to pose barriers to more and more effective use of these interventions.

Health services to screen and treat sexually transmitted infections are still weak

People who seek screening and treatment for sexually transmitted infections face multiple problems. These problems include limited resources, stigma, poor quality of services, and often out-of-pocket expenditures.

Marginalized populations with the highest rates of sexually transmitted infections – such as sex workers, men who have sex with men, people who use drugs, prison inmates, and mobile populations – often do not have access to adequate sexual health services. and teens.

In many circumstances, science, technology and innovation services in low- and middle-income countries are often neglected and underfunded. These problems lead to difficulties in providing screening for asymptomatic infections, insufficient number of trained personnel, limited laboratory capacity, and insufficient supplies of appropriate drugs.