Consequences of STIs: Health Risks of Undetected Infections

Sexually transmitted infections (STIs) such as chlamydia or gonorrhoea often occur without noticeable symptoms, yet if left undetected and untreated, they can lead to serious health consequences. These include chronic pelvic inflammatory disease, pregnancy complications such as premature birth, and an increased risk of further sexually transmitted infections. This article highlights the risks associated with untreated STIs, how you can effectively protect yourself, and how to detect infections in time.

Table of Contents

• What are sexually transmitted infections and how are they transmitted?

• Why do many sexually transmitted infections go unnoticed and untreated?

• What happens if an STI is not treated?

• Selected sexually transmitted infections and their specific consequences

• How can I protect myself from sexually transmitted infections? – 7 essential tips

• Where can I get tested for a sexually transmitted infection?

• When should I get tested for a sexually transmitted infection?

• Summary

What are sexually transmitted infections and how are they transmitted?

Sexually transmitted infections (STIs) are infections transmitted through sexual contact and are a major global health concern. They are classified into three main categories based on the type of pathogen:

• Bacterial infections such as chlamydia, gonorrhoea, and syphilis

• Viral infections such as HIV, HPV (human papillomavirus), genital herpes, and hepatitis B

• Parasitic infections such as trichomoniasis

Transmission usually occurs through unprotected vaginal, anal, or oral sex but can also happen through close skin contact or shared sex toys. Some STIs can also be passed from mother to child during childbirth (Mayo Clinic, 2023).

You're not very familiar with the topic of STIs but want to learn more? In the “Sexually Transmitted Infections” section of our blog, you’ll find a wide range of information on the topic.

Why do many sexually transmitted infections go unnoticed and untreated?

Many STIs go undetected and untreated because they often cause no or only vague symptoms. Some STIs may take years before symptoms appear. A lack of awareness about STIs may result in non-specific complaints—such as mild itching or unusual discharge—being misjudged or ignored. In addition, social stigma may discourage people from seeking medical help. In some cases, limited access to healthcare services or financial barriers can also prevent timely diagnosis and treatment (WHO, 2024).

What happens if an STI is not treated?

Untreated STIs can cause significant health damage in various parts of the body, primarily due to inflammation. This may result from direct damage to tissue by the pathogens or the immune response trying to fight the infection. These inflammatory processes are the main cause of many acute and long-term STI complications. The following overview outlines the general consequences, followed by a discussion of the effects of individual infections.

Overview: Short- and Long-Term Consequences of STIs

Important: Transmission to others is also a major concern with STIs. Infections can be passed on to sexual partners and, during birth, to newborns. Early detection and proper treatment are crucial to preventing both acute symptoms and long-term complications, and to protect both yourself and others (YaleMedicine, 2024).

Selected sexually transmitted infections and their specific consequences

Chlamydia
Chlamydia is one of the most common bacterial STIs, caused by Chlamydia trachomatis. About 70% of infected women and 50% of men show no symptoms. This lack of symptoms contributes to many undetected cases (WHO, 2024). Long-term effects include:

• In women: Pelvic inflammatory disease, infertility, and increased risk of ectopic pregnancies

• In men: Epididymitis (inflammation of the epididymis), which may cause pain and, in rare cases, infertility

Gonorrhoea
Also known as “the clap,” gonorrhoea is caused by the bacterium Neisseria gonorrhoeae. Around 50–80% of infected women and 10–15% of men experience no symptoms, making diagnosis difficult (NHS, 2024). Long-term effects are similar to those of chlamydia:

• In women: Pelvic inflammatory disease, infertility, and ectopic pregnancies. Up to 40% of women with untreated chlamydia or gonorrhoea develop pelvic inflammatory disease (Deal et al., 2004)

• In men: Epididymitis, which may rarely lead to infertility; gonococcal arthritis if the bacteria enter the bloodstream; eye infections in newborns during birth

Syphilis
Syphilis is a bacterial STI caused by Treponema pallidum. It progresses through several stages. Early symptoms like painless sores (primary stage) and rashes (secondary stage) are often mild (NHS, 2022). Long-term consequences may include:

• Damage to the heart and blood vessels

• Severe neurological complications such as neurosyphilis

• Bone and joint damage

• Increased risk of miscarriage or stillbirth in pregnant women

Genital Herpes
Genital herpes is caused by the herpes simplex virus (HSV), usually HSV-2. After the initial infection, the virus remains dormant in the body and can reactivate periodically (NHS, 2023). Long-term effects may include:

• Recurring outbreaks with painful blisters

• In rare cases: complications such as meningitis or neonatal herpes during childbirth

HPV (Human Papillomavirus)
Most HPV infections are harmless and clear up on their own within about two years in 90% of cases. The type of complication depends on the HPV strain. Low-risk types can cause genital warts, while high-risk types are associated with serious outcomes (CDC, 2023):

• Cellular changes (dysplasia) in the cervix, anus, or other mucous membranes, which can lead to cancer if untreated

• Cervical cancer (over 99% caused by HPV)

• Anal cancer (about 90% HPV-related)

• Oral and throat cancers (30–70% linked to HPV)

• Penile cancer (about 50% HPV-related)

HIV (Human Immunodeficiency Virus)
HIV attacks the immune system and can lead to AIDS if untreated. Early symptoms are often mild or non-specific—such as fever, fatigue, or rash—or absent. HIV can remain dormant for years before symptoms appear (Mayo Clinic, 2024). Long-term effects include:

• Immunodeficiency, making the body more vulnerable to infections such as pneumonia, tuberculosis, or fungal diseases

• Chronic inflammation, potentially causing organ damage or cardiovascular issues such as heart attacks or strokes

• Increased cancer risk

• Neurological complications such as HIV-associated neurocognitive disorders (HAND), dementia, or nerve damage

How can I protect myself from sexually transmitted infections? – 7 Essential Tips

1. Regular STI Testing: STI testing is essential for prevention and early detection, especially since many STIs are asymptomatic or present only vague symptoms. Testing helps diagnose infections before they cause harm or are transmitted to others.

2. Protective Measures: Condoms and dental dams act as physical barriers to prevent contact with infectious fluids and mucous membranes. However, since condoms do not protect against all STIs, regular testing remains important.

3. Vaccinations: Vaccines for certain STIs, such as HPV and hepatitis B, offer effective protection against serious complications.

4. Open Communication: Talk openly with your partner(s) about sexual health and potential risks.

5. Avoid Risky Behaviour: Avoid unprotected sex and thoroughly clean sex toys to reduce infection risk.

6. Treatment of Existing Infections: If you suspect an STI, seek treatment promptly to avoid complications and prevent transmission. Inform current and former sexual partners so they can also get tested and treated if necessary.

7. Avoid Alcohol and Drugs Before Sex: Intoxication can impair judgment and increase the likelihood of unprotected sex.

Sources: WHO, 2024; CDC, 2021

Where can I get tested for a sexually transmitted infection?

In Germany, STI tests are available at general practitioners, specialists (e.g. gynaecologists, urologists), public health offices, and counselling centres. At-home self-tests are also available. Routine testing is often offered during pregnancy or for individuals in risk groups.

When should I get tested for a sexually transmitted infection?

STI testing is an important step to protect your health and that of your partners. You should consider getting tested if any of the following apply to you:

• Before starting a new sexual relationship

• After unprotected sex (after a 2–4 week incubation period)

• Once a year if sexually active

• Every 3–6 months if you have multiple partners or belong to a risk group

• If you experience symptoms such as unusual discharge, pain, or itching

• During pregnancy (usually as part of routine check-ups)

Source: CDC, 2024

Summary

Sexually transmitted infections (STIs) are common and often go undetected due to their symptomless or non-specific nature. If left untreated, they can lead to serious health issues such as infertility, chronic conditions, or increased risk of other infections. Effective protection includes proper use of condoms and dental dams, regular testing, vaccinations, and open communication with sexual partners. Preventive measures and early treatment are key to protecting your health and preventing the spread of infections.