23 April 2025 8 min read

Sexually transmitted infections (STIs): how high is your risk?

Cornelia Grabmeier

Cornelia Grabmeier

Health Content Editor

Verified and up to date on 23 April 2025
Sexually transmitted infections (STIs): how high is your risk?

Sexually transmitted infections (STIs) are a topic often shaped by misunderstandings and half-truths. Many people are unaware of their personal risk of contracting an STI or operate under false assumptions that can jeopardize their health. This article examines the most common myths about sexually transmitted infections, compares the myths to the facts, and explains how to better assess your risk and protect yourself.

Table of Contents

How high is the risk of an STI?

In both Germany and the Netherlands, the number of sexually transmitted infections (STIs) continues to rise. The European Centre for Disease Prevention and Control reported a year-on-year increase in Europe of 16% for chlamydia, 48% for gonorrhoea, and 34% for syphilis (ECDC, 2024). 

To assess your infection risk, it may be helpful to know the prevalence of STIs in your country. The table below provides an overview, although there are other STIs with less accessible data.

STI Germany (2022/2023) Netherlands (2023)
Chlamydia Estimated up to approx. 300,000 cases (Barmer, 2024) 24,048 cases (RIVM, 2024)
Gonorrhoea 701 cases of antibiotic-resistant infections (Selb R., et. al., 2024). Total case numbers not available. 13,853 cases (RIVM, 2024)
Syphilis 8,305 cases (in 2022) (Jansen K et al., 2024)  1,693 cases (RIVM, 2024)
HIV 96,700 cases (in 2023) (Adishilfe, n.d.) 141 cases (RIVM, 2024)

 

These factors contribute to contracting an STI

Certain behaviors and circumstances significantly increase the risk of contracting an STI and should be given special attention:

  • Unprotected sex: Vaginal, oral, and anal sex without protection increases STI risk.

  • Multiple partners without regular testing: Increases the likelihood of infection, especially without routine testing.

  • No use of condoms or prevention methods: Raises the risk of transmission.

  • Previous STI infections: Past infections can facilitate reinfection and raise the risk.

  • Drug or alcohol use: Can lead to risky behavior, raising the chance of infection.

  • Needle sharing: Increases the risk of transmitting serious infections such as HIV and hepatitis B/C.

  • Lack of knowledge about transmission routes: Can unknowingly increase the risk of infection.

Source: Mayo Clinic, 2023.

Myths and facts

Myth 1: STIs can only be transmitted through sexual intercourse

STIs can be transmitted in several ways - not just through unprotected sexual intercourse. Some STIs can also spread through skin-to-skin contact, intimate kissing, or the shared use of contaminated objects like razors. Contact with infected blood, such as through shared needles, also poses a potential risk. Furthermore, STIs can be transmitted from mother to child. The following table provides an overview of common STIs and their modes of transmission.

STI Unprotected vaginal sex Unprotected oral sex Unprotected anal sex Kissing Skin-to-skin contact Sharing contaminated items Blood contact Mother-to-child transmission
Chlamydia ✔ ✔ ✔ ❌ ❌ ✔ ❌ ✔
Gonorrhoea ✔ ✔ ✔ ✔ ❌ ✔ ❌ ✔
Syphilis ✔ ✔ ✔ ✔ ✔ (rare) ✔ ✔
HIV ✔ ✔ ✔ ❌ ❌ (rare) ✔ ✔
Herpes ✔ ✔ ✔ ✔ ✔ (rare) ❌ ✔
Trichomoniasis ✔ ✔ ✔ ❌ ❌ ✔ ❌ (rare)
Hepatitis B ✔ ✔ ✔ ❌ ❌ ✔ ✔ ✔
HPV ✔ ✔ ✔ ❌ ✔ (rare) ❌ (rare)

Sources: Cleveland Clinic, 2024; NHS, 2021; CDC, 2024; Sena A., et al., 2024; NHS, 2022; CDC, 2024; CDC, 2024; Cleveland Clinic, 2022; Taheri, M. et al., 2022; GGD Amsterdam, n.d.; CDC, 2024; The New Zealand HPV Project, n.d.

Note: This table offers a general overview of the most common STI transmission routes. Please note that in rare cases, other indirect routes of transmission are possible. For example, if someone has bodily fluids on their hands and touches another person's genitals, transmission is possible even if ordinary skin contact alone would not cause infection.

Myth 2: STIs always cause clear symptoms

STIs often occur without symptoms. If there are no symptoms, infections can be transmitted unknowingly. Regular testing is important, as untreated infections can lead to serious complications such as infertility or chronic illness and can prevent unintentional transmission.

  • Chlamydia: Around 70% of women and 50% of men show few or no symptoms.

  • Gonorrhoea: 65–86% of women and 15–55% of men show no signs of infection.

  • Syphilis: About 50% of infections are asymptomatic and often go unnoticed.

  • HIV: The infection often remains symptom-free for years—sometimes up to 10 years.

  • Herpes: 75–90% of infected individuals experience no or only mild symptoms.

  • HPV: Most infections are asymptomatic and often disappear within two years.

Sources: WHO, 2023, NHS, 2021, WHO, 2024, NHS, 2021, Cleveland Clinic, 2023, Cleveland Clinic, 2022

Myth 3: Condoms offer complete protection against STIs

Condoms significantly reduce the risk of STIs but do not offer full protection. The table below shows how much the risk of STI transmission can be reduced through the use of condoms or other preventive methods. More details can be found [here].

STI Risk reduction with condom use
Chlamydia and Gonorrhoea Around 85% – small amounts can still be transmitted via external mucous membranes
Syphilis 50–70% – transmission possible outside the condom area
HIV Up to 98% – condoms prevent the exchange of bodily fluids
Herpes and HPV Around 70% – partial protection; not all infected areas are covered
Trichomoniasis 70–80% – small amounts may be transmitted outside the condom area
Hepatitis B Up to 90% – condoms block the exchange of infectious fluids

Sources: CDC, 2024; WHO, 2024

Myth 4: Only young people with many sexual partners are at risk of an STI

STIs can affect people of all ages, regardless of how many sexual partners they have. The risk of infection is influenced by specific factors such as unprotected sex, a previous STI infection, or insufficient health screenings (see above: These factors contribute to contracting an STI). Older individuals, in particular, tend to underestimate their personal risk, especially when entering a new relationship. This misconception can lead to neglecting important protective measures. Prevention and responsible health behavior are essential at every stage of life.

Myth 5: STIs can be transmitted via toilet seats

STI transmission via toilet seats is extremely unlikely. STI pathogens survive only briefly outside the human body—typically just a few seconds. They require a warm and moist environment, which a cold and dry toilet seat does not provide. Moreover, the skin that comes into contact with a toilet seat is usually unbroken and intact, meaning there are no open wounds or mucous membranes through which pathogens could enter. More information on this topic can be found [here] (Britannica, 2024; Millar, 2022).

Myth 6: After successful treatment, reinfection is impossible

A successful STI treatment does not provide lasting protection against reinfection. Even after effective treatment, it is still possible to become infected again upon renewed contact with the pathogen (Cleveland Clinic, 2023).

In fact, having an STI increases the risk of contracting another. An existing infection can weaken the natural barrier function of the mucous membranes and trigger inflammation, making it easier for pathogens to enter the body. For example, untreated chlamydia or gonorrhoea can increase the risk of acquiring HIV or other STIs (Alcaide, M. L. et al., 2012).

Myth 7: STI testing is unnecessary and complicated

Getting tested for STIs should not be a source of shame—it is a responsible and courageous step to protect your health and the health of others. The stigma often associated with such testing is unfounded and should not deter anyone from taking care of themselves. Many STIs are asymptomatic and go unnoticed, so regular testing is the only way to get clarity.

STI tests are straightforward and accessible and can be carried out in a clinic, a doctor's office, or at home. With Homed-IQ, you can discreetly and easily test for sexually transmitted infections from the comfort of your home. Depending on your needs, you can choose from different tests: the chlamydia and gonorrhoea test checks for two of the most common STIs; the STI Test Plus tests for seven infections; and the Basic 4 STI Test provides an overview of the four most common STIs. All samples are sent in discreet packaging, analyzed in a certified laboratory, and your results are made available securely and quickly online—no doctor’s visit required.

How can you reduce the risk of getting an STI?

Preventing STIs requires conscious and informed behavior. The following protective measures can help reduce the risk of infection:

  • Use condoms: Protection during vaginal, anal, and oral sex.

  • Regular testing: Especially with changing partners.

  • Vaccinations: Against HPV and hepatitis B.

  • Monogamous relationships: Lower the risk of infection.

  • Open communication: Discuss STI status with partners.

  • Avoid drugs/needle sharing: Reduces indirect infection risk.

Summary

STIs are more common than many people think, and the number of cases in Europe continues to rise. Chlamydia and gonorrhoea are among the most widespread infections. The risk increases through unprotected sex, multiple partners without testing, or high-risk behavior such as drug use. STIs are not only transmitted through sexual intercourse; many are also spread via skin contact or blood. Many infections show no symptoms, which makes regular testing essential. Condoms offer protection but do not cover all routes of transmission. STIs can affect people of all ages, and reinfection is possible even after successful treatment. On the other hand, transmission via toilet seats is extremely unlikely. Responsibility and open dialogue are key to preventing infections.

Frequently asked questions

How reliable are the tests?

Our tests are analysed in an ISO 15189 accredited laboratory with the same equipment and protocols used by hospitals and GPs. The accuracy is comparable to a venous blood draw.

How quickly will I receive my results?

After receipt of your sample at the lab, you will receive your results within 1-2 working days in your personal, secure portal.

Are the tests really anonymous?

Yes, 100%. The packaging is plain, containing no indication of the contents. Your test is registered with an anonymous code. Only you have access to the results.

Sources

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About the author

Cornelia Grabmeier

Cornelia Grabmeier

Health Content Editor

Cornelia Grabmeier holds a BSc in Biology, specialising in neurobiology, from Ludwig Maximilian University of Munich, and is currently pursuing an MSc in Management, Policy Analysis and Entrepreneurship in Health and Life Sciences at Vrije Universiteit Amsterdam. She has completed several research internships, including at the Technical University of Munich Hospital, where she investigated the effects of anaesthetic agents on sleep-wake cycles, and at the Leiden University Medical Centre, where she developed a sandbox for digital health technologies. Cornelia is passionate about making science accessible to a wide audience and inspiring them by communicating fascinating topics. She combines her academic expertise with hands-on research experience to ensure the accuracy and clarity of her work.

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