Sexually Transmitted Infections

Sexually transmitted infections, or STIs, are infections spread by sexual contact. These infections are sometimes also called sexually transmitted diseases, or STDs, and were formerly known as venereal diseases.

Now, STIs can be bacterial, like chlamydia, gonorrhea, and syphilis; viral, such as herpes simplex virus, or HSV; human papillomavirus, or HPV; hepatitis; and human immunodeficiency virus, or HIV; or parasitic, such as in trichomoniasis.

They’re spread through direct contact, including direct sexual contact like vaginal, oral, or anal intercourse; contact with infected blood or other bodily fluids; and even through close body contact.

Additionally, some STIs, such as chlamydia, gonorrhea, syphilis, and HIV, can be spread through vertical transmission, meaning the infection passes from mother to fetus during pregnancy or to the infant during a vaginal birth. In other cases, infections can be transmitted by sharing personal items such as toothbrushes or razors or by sharing needles during IV drug use.

Risk factors for STIs include having multiple sexual partners, especially without an effective barrier such as a condom; being an uncircumcised biological male; and being the receptive partner during intercourse. Also, biological females are at higher risk for infection, partly because the vaginal lining is relatively thin and more easily invaded by pathogens.

Additionally, inadequate screening, lack of access to healthcare, or inadequate risk assessment by healthcare providers all increase the risk that an infected individual unknowingly transmits an STI to another individual. Lastly, STIs can occur at any age, but they’re most prevalent in young adults.

Okay, so, the pathophysiology of STIs depends on the specific infectious agent and site.

So, as an example, a common STI is Neisseria gonorrhoeae, a gram-negative bacterium that causes gonorrhea. The bacteria have hair-like extensions on their surfaces called pili which help the bacteria attach to the mucosal epithelial cells of structures like the vagina, urethra, rectum, or oropharynx. Once the bacteria have attached to the cells, they can then invade the cell, triggering an inflammatory reaction which results in tissue damage.