A sexually transmitted infection (STI) is an infection that is passed from person to person through sexual contact including vaginal, anal, and oral sex. These infections can be caused by bacteria or viruses.
Many bacterial STIs can be treated successfully with antibiotics. However, there is still no cure for viral STIs such as HIV, genital herpes, and human papilloma virus (HPV). Typically, only the symptoms of these infections can be treated, so they can still be passed from one partner to another.
Although STI is often used interchangeably with the term sexually transmitted disease (STD), an STI refers to the presence of pathogenic organisms within the body without the presence of symptoms of disease. An STD, on the other hand, refers to the damage caused by an STI that has progressed. So, although all STDs are preceded by STIs, not all STIs result in an STD.