STDs, or sexually transmitted diseases, are infections that spread through sex (oral, anal, vaginal, and outercourse). The CDC estimates that there are more than 19.7 million new STIs in the United States each year. Half of these infections occur to those aged 15-24. STDs are caused by protozoa, bacteria, or viruses. Many STDs such as herpes and HIV cannot be cured.
A person can have an STD, not know it, but pass it on to someone during sex.
STDs can cause serious health problems (sores, warts, pain, infertility, cancer, and even death).
If you have had sex, you need to see a healthcare professional.