A sexually transmitted infection, or STI, is caused by a virus, bacterium, fungus or parasite that can pass through sexual contact. The term STD is often used when an infection has caused disease or symptoms.

Symptoms are not a reliable test

Possible signs include unusual discharge, pain during urination, sores, blisters, rash or pelvic pain. However, many infections cause no noticeable symptoms. The U.S. Centers for Disease Control and Prevention advises that testing is the only way to know a person’s status.

Prevention

Using condoms correctly every time reduces the risk of many STIs, although infections spread by skin-to-skin contact can still pass from uncovered areas. Vaccines prevent hepatitis B and many HPV-related conditions. Fewer partners, mutual monogamy with a tested partner, and regular screening based on individual risk also reduce exposure.

Testing and treatment

The appropriate tests depend on anatomy, sexual practices, age, pregnancy status, symptoms and exposure history. A routine examination does not automatically include every STI test. Bacterial and parasitic infections may be curable with appropriate medicine; viral infections such as HIV or herpes can be managed but require different care.

Do not use leftover antibiotics or an unverified online treatment. Drug resistance and untreated infection can cause complications and continued transmission. A qualified healthcare service can provide confidential testing, treatment and partner guidance.