A sexually transmitted infection is an infection transmitted through sexual contact, and in many cases it produces no symptoms. Safety comes from testing, partner communication, and barrier methods, not from seeing a symptom. Relying on body appearance is neither diagnosis nor prevention.
The statistics in this text refer to the US or to global estimates, not to Iran.
What is a sexually transmitted infection and how common is it?
A sexually transmitted infection is a collective term for infections transmitted through sexual contact. A 2022 review of US data reports that about 1 in 5 adults had one of these infections in 2018. Between 2015 and 2019, rates of gonorrhea, chlamydia, and syphilis increased in the US. Groups with higher rates include people under 25.
Talking openly and without blame is part of staying safe with a partner — Image: AI-generated
Globally, a 2025 review on syphilis estimates that about 8 million adults aged 18 to 49 acquired syphilis in 2022. In the US, syphilis cases increased by 61% overall from 2019 to 2023. These estimates reflect population burden of infection, not the probability for a specific person.
[Further verification needed: the US and global statistics in these sources cannot be directly generalized to Iran.]
Why do symptoms not always provide warning?
A 2022 review reports that approximately 70% of herpes simplex virus and trichomoniasis infections, and 53 to 100% of extragenital gonorrhea and chlamydia infections, are asymptomatic or minimally symptomatic. Absence of symptoms is not absence of infection. A person may be asymptomatic and unaware of their status.
The same review states that sexually transmitted infections are associated with HIV acquisition and transmission and are a leading cause of tubal infertility in women. Nucleic acid amplification tests for gonorrhea, chlamydia, trichomoniasis, and symptomatic herpes have sensitivity of 86.1 to 100% and specificity of 97.1 to 100%. These estimates relate to test performance, not to clinical interpretation of a result.
A 2025 review on syphilis states that transmission occurs through contact with infectious lesions during vaginal, anal, or oral sex, or through the placenta in pregnancy.
What works to stay safer?
A 2022 review identifies effective preventive interventions as screening, partner notification, and promotion of effective barrier methods. A 2025 review on syphilis recommends screening sexually active people aged 15 to 44 at least once and at least yearly for those at higher risk, and three times in pregnancy.
Counseling about condom use appears in the same framework.
Regarding HPV vaccination, a 2025 cross-sectional analysis based on 6 surveillance studies from 2006 to 2023 on 2,335 girls and young women aged 13 to 26 with sexual experience showed herd protection: vaccine-type HPV positivity decreased among vaccinated and among unvaccinated individuals. In this context, a 2016 review of 6 trials with 359,078 adults on genital chlamydia screening found, in one cluster-controlled trial in the general Dutch population after three annual invitations, no change in chlamydia test positivity (4.1% in the intervention group versus 4.3% in the control group; risk ratio 0.96, 95% confidence interval 0.84 to 1.09; low-quality evidence) and low uptake of the intervention (maximum 16%). This finding concerns a population-based screening program.
What role do shame and stigma play?
A 2020 review states that social stigma remains a barrier to sexually transmitted infection testing and is associated with lower use of prevention services. The same review considers home testing a convenient option. Some people refuse treatment follow-up for fear of unintentional disclosure of their diagnosis. Stigma affects testing, treatment adherence, partner notification, and transmission rates.
In my clinical work, I meet people whose shame has kept them from testing; for this reason, I begin the conversation without judgment and with simple questions.
Our editorial stance is clear: a sexually transmitted infection is a medical and public health question, not a moral judgment about a person.
What does treatment look like?
A 2022 review states that effective treatments exist for bacterial infections and trichomoniasis, while antimicrobial resistance limits oral options for gonorrhea and Mycoplasma genitalium; no curative treatment is available for genital herpes. The practical message is that treatability depends on the type of infection and antimicrobial resistance is part of the picture.
A 2022 review lists screening, partner notification, and barrier methods alongside treatment as effective preventive interventions.
What symptoms does a sexually transmitted infection have?
A 2022 review reports that approximately 70% of herpes simplex virus and trichomoniasis infections, and 53 to 100% of extragenital gonorrhea and chlamydia infections, are asymptomatic or minimally symptomatic. The clinical picture can therefore be empty, and absence of symptoms does not mean absence of infection.
Can a person be infected without symptoms?
Yes. A 2022 review reports the same asymptomatic proportions for several infections and identifies nucleic acid amplification tests with sensitivity of 86.1 to 100% and specificity of 97.1 to 100% for gonorrhea, chlamydia, trichomoniasis, and symptomatic herpes. Testing can diagnose infection even when symptoms are absent.
How can risk be reduced?
A 2022 review identifies screening, partner notification, and promotion of effective barrier methods as effective preventive interventions. A 2025 review also counts counseling about condom use as part of syphilis prevention strategy. These actions reduce risk and do not bring it to zero.
When should a person get tested?
A 2025 review on syphilis proposes screening sexually active people aged 15 to 44 at least once and at least yearly for people at higher risk; in pregnancy, screening three times. A 2020 review also considers home testing a convenient option.
Conclusion: safety comes from testing and communication
A 2022 review shows that about 1 in 5 adults in the US had a sexually transmitted infection in 2018, and in several common infections a large proportion of cases are asymptomatic or minimally symptomatic. A 2025 review estimates that about 8 million adults aged 18 to 49 worldwide acquired syphilis in 2022. Screening, partner notification, and barrier methods are effective preventive interventions.
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Tuddenham S, Hamill MM, Ghanem KG. Diagnosis and Treatment of Sexually Transmitted Infections: A Review. JAMA. 2022;327(2):161-172. DOI: 10.1001/jama.2021.23487. PMID: 35015033
Lee ASD, Cody SL. The Stigma of Sexually Transmitted Infections. Nurs Clin North Am. 2020;55(3):295-305. DOI: 10.1016/j.cnur.2020.05.002. PMID: 32762851
Chevalier FJ, Bacon O, Johnson KA, et al. Syphilis: A Review. JAMA. 2025;334(21):1927-1940. DOI: 10.1001/jama.2025.17362. PMID: 41100079
Low N, Redmond S, Uusküla A, et al. Screening for genital chlamydia infection. Cochrane Database Syst Rev. 2016;9(9):CD010866. DOI: 10.1002/14651858.CD010866.pub2. PMID: 27623210
DeSieghardt A, Ding L, Ermel A, et al. Population-Level Effectiveness and Herd Protection 17 Years After HPV Vaccine Introduction. JAMA Pediatr. 2025;179(12):1326-1334. DOI: 10.1001/jamapediatrics.2025.3568. PMID: 41021257
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Featured and in-text images: AI-generated. No real person is depicted.
