Sexually Transmitted Infections (STIs) Areas of Research

Some of the health complications that arise from STIs include pelvic inflammatory disease, infertility, tubal or ectopic pregnancy, cervical cancer, and perinatal or congenital infections in infants who have been exposed to STIs.


HIV, or human immunodeficiency virus, is the virus that causes AIDS. HIV attacks the immune system by destroying CD4 positive (CD4+) T cells, a type of white blood cell that is vital to fighting off infection. The destruction of these cells leaves people infected with HIV vulnerable to other infections, diseases and other complications. NIAID supports an HIV basic research program that provides valuable scientific information about the basic biology of HIV, the immune response to HIV infection, and potential targets for prevention and therapeutic strategies. Read more about NIAID HIV/AIDS research.


Chlamydia is a common sexually transmitted infection (STI) caused by Chlamydia trachomatis bacteria. It can cause cervicitis in women and urethritis and proctitis in both men and women. Chlamydial infections in women can lead to serious consequences including pelvic inflammatory disease (PID), tubal factor infertility, ectopic pregnancy, and chronic pelvic pain. NIAID and NIAID-supported researchers are studying treatment options for chlamydia infections and developing a vaccine to prevent Chlamydia trachomatis infection. Learn more from the Center for Disease Control and Prevention chlamydia fact sheet.

Genital Herpes

Genital herpes is an STI caused by the herpes simplex viruses type 1 (HSV-1) or type 2 (HSV-2). NIAID supports research on genital herpes and herpes simplex virus (HSV). Studies are currently underway to develop better treatments for the millions of people with genital herpes. While some scientists are carrying out clinical trials to find the best way to use existing medicines, others are studying the biology of HSV. NIAID scientists have identified certain genes and enzymes (proteins) that the virus needs to survive. They are hopeful that drugs aimed at disrupting these viral targets might lead to the design of more effective treatments. Learn more from the Center for Disease Control and Prevention genital herpes fact sheet.

Read the 2023-2028 NIH Strategic Plan for Herpes Simplex Virus Research


Gonorrhea is an STI caused by Neisseria gonorrhoeae bacteria. N. gonorrhoeae infects the mucous membranes of the reproductive tract, including the cervix, uterus, and fallopian tubes in women, and the urethra in women and men. N. gonorrhoeae can also infect the mucous membranes of the mouth, throat, eyes, and rectum. NIAID supports a comprehensive, multidisciplinary program of research on Neissesria gonorrhoeae(gonococci). Researchers are trying to understand how gonococci infect cells while evading defenses of the human immune system. Read more about NIAID research on gonorrhea.

Human Papillomavirus and Genital Warts

HPV is the most common STI. HPV is a different virus than HIV and HSV (herpes). HPV is so common that nearly all sexually active men and women get it at some point in their lives. There are many different types of HPV. Some types can cause health problems including genital warts and cancers. But there are vaccines that can stop these health problems from happening. NIAID conducts and supports research to better understand papillomaviruses and the natural history of HPV infection, develop new diagnostics with more accurate and rapid detection of HPV infections, find new treatments, and examine current HPV prevention strategies and the impact of behavior and age on HPV infection.  Learn more from Center for Disease Control and Prevention HPV fact sheet.

Pelvic Inflammatory Disease

Pelvic inflammatory disease (PID) is a general term that refers to infection and inflammation of the upper genital tract in women. It can affect the uterus (womb), fallopian tubes (tubes that carry eggs from the ovaries to the uterus), ovaries, and other organs related to reproduction. The scarring that results on these organs can lead to infertility, tubal (ectopic) pregnancy, chronic pelvic pain, abscesses (sores containing pus), and other serious problems. PID is the most common preventable cause of infertility in the United States. Scientists supported by NIAID are studying the effects of antibiotics, hormones, and substances that boost the immune system. These studies may lead to insights about how to prevent infertility and other complications of PID.  Learn more from the Center for Disease Control and Prevention PID fact sheet.


Syphilis is an infection caused by Treponema pallidum bacteria. If untreated, syphilis can also lead to more serious symptoms. NIAID-supported researchers are developing new tests that may provide better ways to diagnose syphilis and define the stage of infection. . Efforts to develop a diagnostic test that would not require a blood sample are a high priority. Read more about NIAID research on syphilis.


Vaginitis refers to disorders of the vagina caused by infection, inflammation, or changes in the normal vaginal flora. The three most common diseases diagnosed among women with these symptoms include bacterial vaginosis (40–45 percent), vulvovaginal candidiasis (20–25 percent), and trichomoniasis (15–20 percent). In some cases, there may be more than one disease present. Recurrent vaginitis is also common. Vaginitis is the object of serious studies as scientists try to clarify its role in such conditions as pelvic inflammatory disease and pregnancy-related complications. NIAID-supported research has led to advances in knowledge about the normal microflora of the vagina, reproductive behavior of yeast, and the genetic code of T. vaginalis. Other NIAID-funded researchers have sequenced the genome of T. vaginalis. Learn more from the Center for Disease Control and Prevention bacterial vaginosis fact sheet.

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