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HIV Transmission Happens at All Stages of Care Cascade

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People living with HIV who are not yet aware they are infected, and those who have been diagnosed but are not yet receiving care and treatment, may account for more than 90% of HIV transmission, according to a Centers for Disease Control and Prevention (CDC) study published in the February 23 edition of JAMA Internal Medicine. Moving people through the care cascade could therefore both benefit individuals with HIV and prevent new infections.

Jacek Skarbinski from the CDC's National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention and colleaguesestimated the rate and number of HIV transmissions attributable to people at each stage of the HIV care continuum.

The researchers devised a mathematical model that combined population data from the National HIV Surveillance System with clinical and behavioral data from the National HIV Behavioral Surveillance System and the Medical Monitoring Project. They used the model to estimate the rate and number of transmissions that occurred at each step of the care cascade. Although the analysis was conducted from January 2013 to June 2014, the findings reflect outcomes for people living with HIV in the U.S. in 2009.

Results  

  • The estimated 1,148,200 total people living with HIV in 2009 were distributed as follows:

o   207,600 (18.1%) living with HIV but undiagnosed;

o   519,414 (45.2%) diagnosed but not in ongoing medical care;

o   47 453 (4.1%) retained in care but not prescribed antiretroviral therapy (ART);

o   82 809 (7.2%) prescribed ART but without viral suppression;

o   290 924 (25.3%) with viral suppression or undetectable viral load.

  • People who had HIV but were not yet diagnosed, and people who were diagnosed but not retained in care, accounted for for 91.5% of the estimated 45,000 cases of HIV transmission in 2009 (30.2% and 61.3%, respectively).People who were diagnosed but not retained in medical care were 19% less likely to transmit HIV than undiagnosed individuals (5.3 vs 6.6 transmissions per 100 person-years).
  • People who were engaged in ongoing HIV care but not prescribed ART were 52% less likely to transmit the virus than undiagnosed people.
  • People with viral suppression were 94% less likely to transmit HIV than undiagnosed individuals (0.4 vs 6.6 transmissions per 100 person-years).

"Sequential steps along the HIV care continuum were associated with reduced HIV transmission rates," the study authors concluded. "Improvements in HIV diagnosis and retention in care, as well as reductions in sexual and drug use risk behavior, primarily for persons undiagnosed and not receiving antiretroviral therapy, would have a substantial effect on HIV transmission in the United States."

"These estimates of the relative number of transmissions from persons along the HIV care continuum highlight the community-wide prevention benefits of expanding HIV diagnosis and treatment in the U.S.," they elaborated in their discussion. "Improvements are needed at each step of the continuum to reduce HIV transmission."

Not surprisingly, "the study demonstrates that the steps of the cascade that propel HIV transmission in the U.S. are delayed diagnosis and inadequate retention in care," Thomas Giordano from Baylor College of Medicine wrote in an accompanying editorial. "What is surprising is the magnitude of the effect of those steps."

"Just as there is no single approach to improving adherence to antiretroviral therapy, there likely will be no single approach to improving linkage to and retention in HIV care," he continued. "Human behavior and the health care system are too complex."

"By quantifying where HIV transmissions occur at each stage of care, we can identify when and for whom prevention and treatment efforts will have the most impact," stated Jonathan Mermin, director of CDC's National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, in a CDC press release. "We could prevent the vast majority of new infections tomorrow by improving the health of people living with HIV today."

"Positive or negative, an HIV test opens the door to prevention," said Eugene McCray, director of CDC's Division of HIV/AIDS Prevention. "For someone who is positive, it can be the gateway to care and the signal to take steps to protect partners from infection. For someone who tests negative, it can be a direct link to important prevention services to help them stay HIV-free."

2/24/15

Reference

J Skarbinski, E Rosenberg, G Paz-Bailey, et al.Human Immunodeficiency Virus Transmission at Each Step of the Care Continuum in the United States. JAMA Internal Medicine. February 23, 2015 (Epub ahead of print).

TP Giordano. The HIV Treatment Cascade -- A New Tool in HIV Prevention.JAMA Internal Medicine. February 23, 2015 (Epub ahead of print).

Other Sources

JAMA Network.HIV Transmission at Each Step of the Care Continuum in the United States. Press release. February 23, 2015.

CDC. 9 in 10 New U.S. HIV Infections Come from People Not Receiving HIV Care. Press release. February 23, 2015.