STIs – What are sexually transmitted infections (STIs)?
Sexually transmitted infections (STIs) are infections that can be passed on during sex – through contact with mucous membranes, body fluids, or tiny skin injuries. This can happen during vaginal, anal, or oral sex, but also through sharing sex toys or other objects.
Many STIs cause no noticeable symptoms at first. Still, if left untreated, they can lead to health problems – and be passed on to others. Most STIs are treatable, and some can even be cured completely.An open and informed approach to sexuality and health helps protect yourself and others.
Chlamydien
Chlamydia are bacteria and among the most common STIs worldwide. They can affect the genital area, anus, or throat – depending on sexual practices.
Symptoms
Often no noticeable complaints
Burning when urinating
Discharge from vagina, penis, or anus
Pain during sex or in the lower abdomen
For people with a vagina: spotting or unusual discharge
Anal or throat infections: often without symptoms
If left untreated, chlamydia can cause complications, e.g. infections of the uterus, fallopian tubes, or testes – which may reduce fertility.
Treatment: Chlamydia are easily treated with antibiotics – often with a single dose.
Recommendation
Regular testing if you have new or changing partners
In Germany, statutory health insurance covers one annual test for people with a vagina under 25
Gonorrhoe ("The clap")
Gonorrhea is a bacterial infection that can affect the genital area, anus, and throat.
Symptoms
Yellow-green discharge from penis, vagina, or anus
Burning when urinating
Pain or itching in the anal area
Throat infections often without symptoms – but still transmissible
If untreated, gonorrhea can cause inflammation, infertility, and chronic pain.
Treatment: Antibiotics. Because of resistant strains, therapy is often adjusted individually.
Important
Sexual partners should be tested and, if necessary, treated as well
A follow-up test is recommended to confirm treatment success
Syphilis
Syphilis is a bacterial STI that progresses in stages – sometimes over months or years.
Symptoms
Early stage: painless sore (e.g. on genitals, anus, or mouth)
Second stage: rash, flu-like symptoms, swollen lymph nodes
Late stage (if untreated): damage to organs, brain, and nerves
Treatment: Syphilis is easily treated with penicillin. If diagnosed early, it can be cured completely.
Recommendation
Regular testing, especially if you have multiple or changing partners
Particularly important for men who have sex with men, trans*, and non-binary people at higher risk
HIV
HIV is a virus that weakens the immune system. Untreated, it can lead to AIDS. Today, HIV is very well treatable with medications that stop viral replication. People with HIV can live healthy lives and cannot transmit the virus if treatment is effective.
Symptoms
Early weeks: flu-like symptoms (fever, night sweats, swollen lymph nodes)
Afterwards: often no noticeable signs for a long time
Treatment: Antiretroviral therapy (ART) suppresses the virus in the body. If successful, HIV becomes undetectable – and untransmittable (U=U).
Protection
Condoms
PrEP: daily pill for HIV-negative people at higher risk
PEP: emergency medication within 48–72 hours after a possible risk
Hepatitis A
Hepatitis A is liver inflammation caused by a virus. It spreads via contaminated food or fecal-oral transmission during sex – e.g. through anal contact.
Symptoms
Nausea, vomiting, abdominal pain
Fatigue, fever
Later sometimes jaundice (yellow skin/eyes)
Treatment: Hepatitis A usually clears on its own. No special therapy needed.
Protection
Vaccination provides reliable protection
Especially recommended for anal practices, travel to high-risk regions, or communal settings
Hepatitis B
Hepatitis B is a highly contagious viral liver infection. Transmitted via blood, semen, vaginal fluids, and other body fluids.
Symptoms
Fatigue, nausea, abdominal pain
Sometimes jaundice
Often no noticeable complaints
Treatment
Acute infections often clear spontaneously
Chronic infections require regular monitoring and possible treatment
Protection
Vaccination is widely recommended, including in childhood
Especially important for sexually active people with multiple partners
Hepatitis C
Hepatitis C is a viral infection transmitted via blood – historically via contaminated needles, today also through sex, especially anal practices with blood contact.
Symptoms
Often no symptoms for a long time
Later: fatigue, abdominal pain, liver problems
Treatment: Hepatitis C can now be cured with modern medication – usually 8–12 weeks of treatment.
Protection
Avoid blood contact
Use condoms and gloves (e.g. for fisting)
Clean shared sex toys thoroughly
Counseling & Testing at SeGe Köln
Many STIs go unnoticed – regular testing is key to sexual health. We offer confidential, open, and non-judgmental counseling. Even if you have no symptoms, you are welcome here.
All genders and sexual identities are welcome.
We provide information, testing, and treatment – competent, safe, and free of discrimination.
Other sexually transmitted pathogens include:
HPV (human papillomavirus): can cause genital warts and cancer
Mycoplasma & Ureaplasma: often involved in genital infections
Genital herpes (HSV): causes painful blisters around genitals or anus
Trichomoniasis: parasites that cause discharge and itching
Scabies: mites transmitted through close body contact
Condylomas (genital warts): caused by certain HPV strains
Even if your symptoms are unclear or recurring, we are here for you – whether it’s a known STI or something that needs further clarification.
Mycoplasma (M. Gen)
M. Gen is a bacterial STI. Transmission risk is lower than for chlamydia. It is mainly found in the genital tract, less often in the rectum or throat.
Do I need to be tested?
Usually no.
In the general population, only 1–2% carry M. Gen.
In STI clinics, rates vary between 4–38%.
Many people have no symptoms, and the infection can clear on its own.
When is testing useful?
Only if:
you have symptoms, and
chlamydia and gonorrhea have already been ruled out
Possible symptoms:
Burning when urinating
Discharge from penis or vagina
Lower abdominal pain
Spotting or bleeding after sex
Do my partners need testing or treatment?
The incubation period is 1–3 weeks. Testing before that is not useful.
Only regular sexual partners should be treated to avoid reinfection.
Important to know:
Treatment options are not always reliable.
Overuse of antibiotics can cause resistance.
A “test of cure” 6 weeks after treatment is recommended. About 20% may still test positive temporarily.