October 3, 2013
In high-income countries such as Canada, Australia and the U.S. and regions such as Western Europe, HIV infections continue to spread, particularly among men who have sex with men (MSM).
New York City was one of the first urban regions hard hit by the emerging HIV epidemic in the 1980s. Research in that city has revealed that in 2010 nearly 50% of new HIV/AIDS diagnoses were among MSM.
Public health workers in New York City have found that many MSM have a large burden of sexually transmitted infections (STIs), such as chlamydia, gonorrhea and syphilis.
Numerous studies have found a link between the presence of an STI and increased risk for becoming infected with HIV. STIs can do this because they can injure the delicate tissue on or inside the anus, genitals, mouth and throat. STIs can also cause inflammation. The sores (sometimes painless) or lesions associated with STIs in these tissues can provide a point of entry for HIV (and other germs) into the body.
Researchers in New York City conducted an analysis of data collected from STI clinics over the past several years. In those clinics, people who sought care were offered rapid HIV testing. MSM whose rapid test results were negative were offered more accurate tests that can identify HIV's genetic material.
MSM who disclosed that they had unprotected receptive anal intercourse were also offered STI testing (for chlamydia and gonorrhea) using rectal swabs.
The researchers analysed data collected between January 2008 and March 31, 2010. They compared rates of HIV infection among 552 MSM with and without rectal STIs. Participants were roughly the same age and had similar risk behaviours.
The researchers found that having a rectal STI significantly increased the risk of becoming infected with HIV. That is, one in 15 MSM who had a rectal STI and who were initially HIV negative were subsequently diagnosed with HIV, usually within a year of the STI diagnosis. Troublingly, most of the men were unaware that they had rectal STIs because in more than 70% of cases such infections were symptom free.
According to the researchers' calculations, about 7% of 276 MSM who had rectal STIs became HIV positive each year of the study. In contrast, about 3% of the 276 other MSM who did not have rectal STIs became infected with HIV each year of the study. This difference in HIV infection rates was statistically significant; that is, not likely due to chance alone. Overall, being diagnosed with a rectal STI increased the risk of subsequent HIV infection more than two-fold.
New HIV infections were very high among some subgroups, as follows:
According to the researchers, MSM who were black and diagnosed with rectal STIs were five-fold more likely to subsequently develop HIV compared to white MSM with both rectal STIs.
Researchers also tested participants for early-stage syphilitic infection but found that although relatively common it did not appear to play a statistically significant role in the spread of HIV. However, other studies have found that syphilis does play a role in the growing HIV epidemic, particularly in MSM.
Although not a focus of the present New York study, other studies have found that the use of alcohol and/or party drugs by some MSM may play a role in enabling unsafe behaviours, rendering users vulnerable to HIV.
The finding that many cases of rectal STIs were symptom free meant that the men were not aware that they had these infections. As a result, the New York City researchers stated that their results "underscore the need for routine rectal screening of patients who report unprotected anal intercourse."
The researchers encourage doctors and nurses to do the following:
"Take a nonjudgmental and confidential sexual history that ascertains the sex of a patient's sex partners and anatomic sites of sexual exposure."
Furthermore, they add that healthcare providers' encounters with patients are an ideal time to provide education about risk factors for becoming infected with HIV. Such encounters are an opportunity to intervene in order to decrease HIV risk behaviour.
The New York City researchers also recognized growing barriers to STI care in their region, such as the following:
The researchers note that MSM who have rectal STIs could be targeted for counselling about receiving pre-exposure prophylaxis (PrEP). The main part of PreP interventions (in addition to safer sex counselling and frequent testing for STIs and HIV) involves the use of two anti-HIV drugs -- tenofovir and FTC -- co-formulated in a single pill called Truvada. In clinical trials with MSM, daily Truvada compared to placebo reduced the overall risk of HIV infection by 44%. Truvada's preventive ability was greater in MSM who took the pill exactly as directed.
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