Rates of sexually transmitted infections (STIs) in Canada are on the rise. Research suggests that STIs can increase both a HIV-negative person’s risk of becoming infected with HIV and an HIV-positive person’s risk of transmitting HIV to someone else. This article explores how STIs may increase the risk of sexual HIV transmission, how STIs may be undermining our HIV prevention strategies, and what we can do about it. The basics There are many different types of STIs. Some of the more common ones include gonorrhea, chlamydia, Trichomonas vaginalis, human papillomavirus (HPV), herpes and syphilis. Some of these (such as herpes and syphilis) cause ulcers on the genitals or rectum, while others (such as gonorrhea, chlamydia, and Trichomonas vaginalis) can cause painful urination and/or discharge. HPV can cause the growth of genital warts on or around the genitals or rectum. Most STIs can also infect the mouth and throat.
STIs can cause swelling, redness and pain in the infected area. However, many people who have an STI have no symptoms at all—this is known as being asymptomatic—so neither they nor their partner may realize they are infected. Although hiv pep singapore all STIs are treatable, only some can be cured through treatment and completely cleared from the body. STIs that can be cured through treatment include gonorrhea, chlamydia, syphilis and Trichomonas vaginalis. STIs that can be managed through treatment, but not cured, include HPV, herpes and HIV.
How do STIs cause inflammation?
To understand how STIs increase the risk of HIV transmission, we need to understand what STIs do once they come in contact with our mouth, genitals or rectum. Sexually transmitted infections are caused by bacteria, viruses and parasites, also known as germs. When germs enter the body, they are recognized by the immune system, which, as part of the body’s response to infection, starts a process known as inflammation. This leads to the symptoms associated with many STIs, such as redness, swelling and pain. The inflammatory process “activates” our immune cells to fight germs and recruits more immune cells to the site of the infection, helping the body clear the germs. For example, if someone has a vaginal STI, then the inflammatory response will recruit more immune cells to the lining of the vagina. How do STIs increase the risk of becoming infected with HIV? Research suggests that HIV-negative individuals with an STI may be at increased risk of becoming infected with HIV through anal sex, vaginal sex, frontal sex (a term used by some trans people to refer to sex using genitals on the front of the body) and oral sex.1 But how do STIs increase someone’s risk of HIV infection?
Scientists believe that inflammation plays an important role. Inflammation increases the concentration of “activated” immune cells in the area infected with the STI. Although the inflammatory response is meant to help fight the sexually transmitted infection, HIV likes to infect some of these recruited immune cells, also known as CD cells. Also, HIV finds it easier to infect, and replicate in, CD cells that are “activated”. Therefore, if someone has an STI in the mouth, genitals or rectum, and that area is exposed to HIV, the higher concentration of “activated” CD cells facilitates HIV infection, replication and spread throughout the body. All types of STIs cause inflammation and therefore may increase the risk of becoming infected with HIV in this way. Also, some types of STIs increase the risk of HIV infection through ulcers, which create “holes” or ways for HIV to enter the body through the mouth, genitals or rectum.
How do STIs increase the risk of transmitting HIV?
Research suggests that HIV-positive individuals with an STI may be at increased risk of passing HIV to someone else through anal, vaginal and frontal sex. But how do STIs increase someone’s risk of transmitting HIV? Again, it comes down to inflammation. If a person living with HIV has an STI, then inflammation will “activate” and recruit more immune cells to the infected genitals or rectum. Some of the immune cells in a person living with HIV are already infected with HIV, therefore the inflammatory response brings more HIV (contained in the infected immune cells) to the site of the STI in the genitals or rectum. Consequently, more HIV enters the body fluids in that area. For example, a vaginal STI increases the amount of the virus (viral load) in the vaginal fluid. Research shows that the more virus there is in the body fluids of a person living with HIV the higher the risk of passing HIV to someone else. HIV also replicates, or makes more HIV, quicker in immune cells that have been “activated” through inflammation, compared to immune cells that are not “activated.” STI rates on the rise In Canada, the rate of new STIs is on the rise. According to the latest report published by the Public Health Agency of Canada, over the past decade chlamydia and gonorrhea rates have increased almost twofold, while syphilis rates have increased more than eightfold (see table).