Sexually Transmitted Disease (STD)
Infections spread mainly through sexual contact
Quick Facts
- Type: Infectious conditions
- Spread by: Vaginal, anal, or oral sex; sometimes skin contact
- Key point: Many cause no symptoms
- Prevention: Condoms, testing, vaccines
Overview
Sexually transmitted diseases (STDs), also called sexually transmitted infections (STIs), are infections passed mainly through vaginal, anal, or oral sex, and sometimes through close skin-to-skin contact. They are caused by bacteria, viruses, or parasites and are very common worldwide.
An important feature of many STDs is that they cause no symptoms, so a person can have and spread an infection without knowing it. This is why testing is so important. Many STDs are easily cured with treatment, and others can be effectively managed. Left untreated, some can cause serious complications, including infertility and increased risk of other infections.
Symptoms
Symptoms vary widely by infection, and many people have none at all. When symptoms occur, they may include:
- Unusual discharge from the penis, vagina, or anus
- Pain or burning when urinating
- Sores, bumps, blisters, or warts on or around the genitals, anus, or mouth
- Itching, redness, or irritation in the genital area
- Pain during sex or in the lower abdomen or pelvis
- Unusual vaginal bleeding
- Flu-like symptoms or rashes with some infections
Because symptoms can be mild, intermittent, or absent, testing is the only reliable way to know your status.
Causes
STDs are caused by infectious organisms passed during sexual contact.
- Bacteria: Causes of infections such as chlamydia, gonorrhea, and syphilis, which are usually curable with antibiotics.
- Viruses: Including those causing genital herpes, human papillomavirus (HPV), HIV, and hepatitis B; these are managed rather than always cured.
- Parasites: Such as trichomoniasis and pubic lice.
Most spread through vaginal, anal, or oral sex, while some, like herpes and HPV, can pass through skin-to-skin contact. A few can also be transmitted through blood or from a pregnant person to their baby.
Risk Factors
- Having sex without a condom or other barrier protection
- Having multiple or new sexual partners
- A partner who has an STD or multiple partners
- A previous STD
- Not being vaccinated against HPV or hepatitis B
- Exchanging sex for money or drugs, and certain drug or alcohol use that affects judgment
Diagnosis
Because many STDs are silent, testing is essential and is the only reliable way to diagnose them.
- Urine tests: Commonly used for chlamydia and gonorrhea.
- Blood tests: Used for HIV, syphilis, and hepatitis.
- Swabs: Of the genitals, throat, anus, or a sore to detect specific infections.
- Physical examination: To check for sores, warts, discharge, or other signs.
Routine screening is recommended for sexually active people based on age, risk factors, and pregnancy, even without symptoms.
Treatment
Treatment depends on the type of infection.
- Bacterial and parasitic STDs: Such as chlamydia, gonorrhea, syphilis, and trichomoniasis are usually cured with antibiotics or antiparasitic medicine.
- Viral STDs: Such as herpes and HIV cannot be cured but can be controlled with medication that reduces symptoms, complications, and the chance of spreading them.
- Treating partners: Sexual partners often need testing and treatment to prevent reinfection.
- Follow-up: Some infections require repeat testing to confirm they are cleared.
It is important to complete the full course of any prescribed medicine and to avoid sex until treatment is finished and a clinician advises it is safe.
Prevention
STDs are largely preventable with a combination of measures:
- Use condoms or other barriers correctly and consistently
- Get vaccinated against HPV and hepatitis B
- Get tested regularly, and before new sexual relationships
- Limit the number of sexual partners and talk openly about testing
- For HIV, preventive medication (PrEP) is an option for people at higher risk
- Avoid sharing needles or other injection equipment
When to See a Doctor
See a doctor or visit a clinic if you have any symptoms such as discharge, sores, genital itching, painful urination, or pelvic pain, or if a partner tells you they have an STD. Testing is also wise after unprotected sex with a new partner, even without symptoms.
Seek prompt care for severe pelvic or abdominal pain, high fever, painful sores with fever, or testicular pain and swelling, as these can signal a complication. If you may have been exposed to HIV very recently, contact a clinic urgently, as preventive medication can be most effective when started quickly.
Frequently Asked Questions
Can I have an STD without any symptoms?
Yes. Many STDs, including chlamydia and gonorrhea, often cause no symptoms at all, so a person can carry and spread an infection without knowing. This is why regular testing is the only reliable way to know your status.
Which STDs can be cured?
Bacterial and parasitic STDs such as chlamydia, gonorrhea, syphilis, and trichomoniasis are usually curable with medication. Viral STDs like herpes and HIV cannot be cured but can be effectively managed with treatment.
How often should I get tested?
It depends on your age, number of partners, and risk factors. Sexually active people, especially with new or multiple partners, should be tested regularly, and pregnant people are routinely screened. A clinician can advise on the right schedule for you.
How can I lower my risk of getting an STD?
Use condoms correctly and consistently, get vaccinated against HPV and hepatitis B, limit partners, and get tested before new relationships. For people at higher risk of HIV, preventive medication (PrEP) is an option to discuss with a doctor.
What symptoms mean I should seek care quickly?
See a clinician for any discharge, sores, genital itching, or painful urination. Seek prompt care for severe pelvic or abdominal pain, high fever, or testicular pain and swelling, and contact a clinic urgently if you may have been recently exposed to HIV.
References
- Centers for Disease Control and Prevention (CDC). Sexually Transmitted Infections.
- World Health Organization (WHO). Sexually transmitted infections (STIs).
- MedlinePlus, U.S. National Library of Medicine. Sexually Transmitted Diseases.
- Office on Women's Health, U.S. Department of Health and Human Services.