STI: Meaning, Symptoms, Testing, Treatment, and Prevention

Common STIs include:

• chlamydia;
• gonorrhea;
• syphilis;
• genital herpes;
• HPV;
• trichomoniasis;
• HIV;
• hepatitis B.

Simple examples include:

• An STI may be present without symptoms.
• An STI can spread during oral, vaginal, or anal sex.
• Condoms can lower the risk of many STIs.
• Testing is often the only way to know whether someone has an STI.
• Some STIs are curable, while others can be treated and managed.

A person cannot identify an STI simply by looking at someone’s body, hygiene, relationship status, or sexual history.

• an STI;
• one STI;
• several STIs;
• an untreated STI.

Common expressions include:

• have an STI;
• acquire an STI;
• transmit an STI;
• test for STIs;
• treat an STI;
• prevent STIs.

Examples include:

• She requested an STI test.
• Some STIs cause no symptoms.
• The clinic provides confidential STI care.

Use an STI, not a STI, because the spoken abbreviation begins with the vowel sound ess.

An infection occurs when a bacterium, virus, parasite, or another organism enters the body. Disease develops when that infection causes symptoms, complications, or damage.

For example, someone may have a chlamydia infection without symptoms. If the untreated infection later causes pelvic inflammatory disease, it has produced a disease complication.

Healthcare professionals increasingly use STI because infection can exist and spread before disease becomes noticeable. The CDC’s STI information center uses the term broadly for sexually transmitted infections, testing, prevention, and care.

• vaginal sex;
• anal sex;
• oral sex;
• genital skin-to-skin contact;
• contact with infected sores or lesions;
• sharing needles or injection equipment;
• sharing uncovered or improperly cleaned sex toys;
• pregnancy, childbirth, or breastfeeding for certain infections;
• blood exposure in specific circumstances.

Different infections spread in different ways. Ejaculation is not required for every STI to be transmitted.

Some infections, including herpes, HPV, and syphilis, may spread through affected skin that a condom does not fully cover.

Bacterial STIs

Examples include:

• chlamydia;
• gonorrhea;
• syphilis;
• chancroid;
• Mycoplasma genitalium infection.

Many bacterial STIs can be cured with appropriate antibiotics. The exact medicine depends on the infection, current treatment guidance, allergies, pregnancy, and possible antibiotic resistance.

Viral STIs

Examples include:

• genital herpes;
• HPV;
• HIV;
• hepatitis B.

Some viral STIs remain in the body, but treatment may control symptoms, prevent complications, or greatly reduce transmission.

Parasitic STIs

Examples include:

• trichomoniasis;
• pubic lice;
• scabies transmitted through close sexual contact.

These infections are generally treatable with suitable medication.

The World Health Organization’s STI fact sheet explains that more than 30 bacteria, viruses, and parasites may be transmitted through sexual contact and that many infections are asymptomatic.

• unusual vaginal, penile, or anal discharge;
• burning or pain during urination;
• genital, anal, or oral sores;
• blisters, bumps, or warts;
• genital itching or irritation;
• pelvic or lower abdominal pain;
• testicular pain or swelling;
• pain during sex;
• unusual bleeding;
• rash;
• fever or swollen lymph nodes.

These symptoms can also result from conditions that are not sexually transmitted. Testing and professional assessment are needed for an accurate diagnosis.

Someone may feel completely healthy while carrying and transmitting an infection. An untreated STI may still affect fertility, pregnancy, internal organs, or sexual partners.

The absence of symptoms does not prove that a person is free from infection. It is also possible for symptoms to appear, disappear, and later return.

• a urine sample;
• a blood sample;
• a vaginal swab;
• a throat swab;
• a rectal swab;
• a swab from a sore or discharge;
• a physical examination.

No single test detects every STI. Testing should match the body areas involved in sexual activity.

For example, a urine test may not detect an infection located only in the throat or rectum. Some infections also have a window period, during which they may be too recent to appear on a test.

Testing needs and frequency depend on factors such as age, pregnancy, symptoms, sexual activities, number of partners, location, and previous infections. The CDC’s current STI testing guidance explains available testing methods and recommends discussing personal sexual practices with a healthcare professional to choose suitable tests.

Treatment may include:

• antibiotics;
• antiviral medicine;
• antiparasitic medicine;
• medicine to control symptoms;
• monitoring for complications;
• vaccination or preventive care for partners when appropriate.

A person should take prescribed medicine exactly as directed and should not use another person’s medication or leftover antibiotics.

Sexual contact may need to pause until treatment is completed, the recommended waiting period has passed, and relevant partners have been tested or treated.

• chlamydia;
• gonorrhea;
• syphilis;
• trichomoniasis.

Other STIs may not currently be eliminated from the body but can often be managed:

• herpes outbreaks may be treated or suppressed;
• HIV can be controlled with antiretroviral treatment;
• hepatitis B can be monitored or treated;
• many HPV infections clear naturally, while related warts or abnormal cells can be treated.

A positive result does not mean that someone cannot have healthy relationships, satisfying sex, pregnancy, or family life.

• using external or internal condoms correctly;
• using dental dams during oral sex;
• receiving HPV and hepatitis B vaccines;
• having appropriate STI tests;
• discussing testing and prevention with partners;
• limiting sexual exposure when desired;
• cleaning sex toys and changing barriers between users;
• avoiding shared injection equipment;
• using HIV PrEP when appropriate;
• obtaining HIV PEP urgently after a qualifying exposure;
• using doxycycline PEP only when medically recommended for an eligible person.

Birth-control pills, implants, injections, rings, and IUDs can prevent pregnancy but do not protect against STIs.

Protection is generally strongest for infections transmitted mainly through bodily fluids. Condoms may provide less complete protection against infections spread through uncovered skin, sores, or warts.

A new condom should be used:

• for every separate sexual act;
• with each new partner;
• when moving between the anus and vagina;
• when a sex toy is shared.

Using two condoms together may create extra friction and increase the chance of tearing.

The HPV vaccine protects against important HPV types associated with genital warts and several cancers.

The hepatitis B vaccine protects against hepatitis B, which can spread through sexual contact or blood.

Hepatitis A vaccination may also be recommended for some people based on sexual practices, health conditions, travel, or local medical guidance.

Vaccination does not replace testing, barriers, or communication.

A respectful conversation may include:

• the infection diagnosed;
• when possible exposure may have occurred;
• which tests are recommended;
• whether treatment is available;
• whether sexual activity should pause;
• which prevention methods may be needed.

An STI result does not always reveal when or from whom the infection was acquired. Some infections may remain unnoticed for a long time.

Partner communication should focus on health and prevention rather than blame, humiliation, threats, or public exposure.

Possible complications may include:

• miscarriage;
• premature birth;
• newborn infection;
• congenital syphilis;
• eye or neurological problems;
• transmission of HIV or hepatitis.

Early testing and suitable treatment can prevent many complications. Pregnancy-related STI care should be discussed with a qualified healthcare professional.

• condom use;
• STI testing;
• treatment;
• known infection status;
• sexual activity with other partners.

A person should not deliberately lie about information that is necessary for another person to make an informed sexual-health decision.

However, an STI diagnosis does not remove someone’s right to privacy. Disclosure should be limited to people who genuinely need the information, such as relevant partners and healthcare professionals.

Having an STI does not mean that someone is:

• dirty;
• promiscuous;
• careless;
• unfaithful;
• undeserving of intimacy.

STIs are health conditions. Respectful language makes it easier for people to seek testing, complete treatment, notify partners, and prevent further transmission.

A healthy-looking person cannot have an STI.
Appearance does not reveal infection status.

Oral sex cannot transmit STIs.
Several infections may spread through oral sexual contact.

Birth control prevents STIs.
Most contraceptive methods prevent pregnancy but provide no STI protection.

Every STI can be cured with antibiotics.
Antibiotics treat bacterial infections, not viral infections.

An STI diagnosis proves recent infidelity.
Some infections can remain undetected for months or years.

1. An STI is an infection that may spread through sexual contact.
2. An STI may be present even when no symptoms are visible.
3. Can an STI spread through oral or anal sex?
4. The patient requested an STI test after a possible exposure.
5. A condom can reduce the risk of transmitting many STIs.
6. One urine test does not detect every possible STI.
7. A bacterial STI may be curable with appropriate antibiotics.
8. A viral STI may be treatable even when it cannot be eliminated.
9. An STI diagnosis should be discussed without shame or blame.
10. Preventing an STI may involve barriers, vaccination, testing, communication, and preventive medicine.

Many STIs are asymptomatic, so appearance, trust, cleanliness, or relationship status cannot replace appropriate testing. Barriers, vaccination, honest communication, and preventive medicine can lower risk.

Accurate sexuality education uses nonjudgmental language and encourages timely testing and treatment. An STI diagnosis does not remove anyone’s right to privacy, affection, relationships, consent, or a satisfying sexual life.