December 8, 2014
Black men who have sex with men (MSM) in the U.S. experience higher rates of HIV transmission than white MSM -- not because they engage in riskier behaviors, but because of racial disparities in HIV prevalence and across the HIV care continuum, according to a study published in The Lancet HIV.
The study, entitled "Understanding the HIV Disparities Between Black and White Men Who Have Sex With Men in the USA Using the HIV Care Continuum: A Modelling Study," used 2009 to 2010 data from the U.S. Centers for Disease Control and Prevention to estimate separate HIV care continuums for black and white MSM in the U.S.
The authors explain that "The HIV care continuum has become an important model for the measurement of HIV/AIDS care in populations through nested steps of HIV infection, diagnosis, retention in care, prescription of antiretroviral therapy, and viral suppression." Viral suppression is known to greatly reduce the risk of onward HIV transmission.
They found consistent disparities at each step of the continuum, most notably in retention in care:
Due to higher HIV prevalence (the proportion of a population living with HIV) and lower rates of viral suppression among black MSM, the study found that equivalent risk behaviors among black MSM conferred a higher probability of HIV exposure than among white MSM.
"Because disparities in the HIV care continuum likely account for most of the disparities in HIV transmission rates between black and white MSM, there is an urgent need to improve our rates of HIV testing, linkage and retention in care, and prescription of and adherence to antiretroviral therapy for black MSM living with HIV," the study explained. "Additionally, important socioeconomic disparities between white and black MSM need to be addressed because these might negatively affect the effectiveness of the interventions in the care continuum."
If black MSM received the same level of HIV care as white MSM, the researchers predicted the gap in new infection rates would be reduced by 27%.
However, the study highlighted challenges in addressing higher rates of transmission among black MSM because of existing disparities in HIV prevalence. Even with racially equivalent care, mathematical modelling predicted black MSM would still have an estimated HIV incidence (the number of new HIV infections) five to eight times that of white MSM.
The study recommended increased investment at each step of the care continuum, from diagnosis to viral suppression, but cautioned that racial disparities in HIV transmission would likely persist for decades.
"These findings suggest that, even if disparities in transmission rates are addressed, the higher HIV prevalence in black MSM will continue to compound disparities in HIV incidence for many years to come," the study explained. "Reversal of this trend will only be possible through a sustained reduction in the HIV transmission rate to less than 1 [infection per 100 people living with HIV each year] for a sufficient period to allow a reduction in the current number of prevalent HIV-positive black MSM and an increase in HIV-negative cohorts in successive generations."
"Our data show the urgent need for research towards a cure or a highly effective HIV vaccine, or both," the study concluded. "In the absence of such transformational biomedical advances in HIV prevention, disparities by race in HIV incidence rate in MSM are likely to persist in the US epidemic in the foreseeable future."
Katherine Moriarty is a consultant and freelance writer, based in Vancouver. She has 10 years of experience in the intersecting fields of public health and community development, with a focus on bloodborne virus policy and programming.
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