U.S. HIV transmission rates declined overall in 2016 yet remained high among those who do not know their status, according to a study published on March 18 in the Morbidity and Mortality Weekly Report (MMWR) released by the Centers for Disease Control and Prevention (CDC). The study also reports that persons living with HIV who are not receiving HIV care accounted for more than 80% of new U.S. HIV transmissions in 2016.
CDC researchers used the Progression and Transmission of HIV (PATH 2.0) model to analyze data from both National HIV Behavioral Surveillance and the National HIV Surveillance System.
They updated their model for estimating the 2016 transmissions to establish where along the HIV care continuum (e.g., not yet diagnosed, diagnosed but not linked to care, engaged in care, and virally suppressed) transmissions are more likely to occur among the most vulnerable groups: men who have sex with men [MSM], injection drug users, MSM who inject drugs, and heterosexual men and women. The study did not say whether transgender persons were included in any of these categories.
Those who are in care and virally suppressed -- the final group in the HIV care continuum -- had a zero transmission rate, which supports the data showing that an undetectable viral load prevents HIV transmission.
The transmission rate among people with acute infection who were unaware of their status was 16.1 per 100 person-years, and the rate was 8.4 per 100 person-years for persons with a chronic infection who were unaware of their status. Persons aware of their HIV status but out of care followed at 6.6. Persons engaged in HIV care but not virally suppressed had a rate of 6.1.
MSM remain the hardest hit by new transmissions. In 2016, MSM living with HIV transmitted the virus at a rate of 4.4 transmissions per 100 person-years, with the category of MSM who inject drugs at 3.8. Injection drug users, stratified by sex, followed with a 3.6 transmission rate for men and a 2.2 transmission rate for women. Heterosexual men had a 2.7 transmission rate, while heterosexual women had a 1.2 transmission rate.
But this study, according to CDC, also shows some promising news. Each of the continuum's intervals marked a decline from six years prior. The 2016 results indicated a 3.5 per 100 person-years rate, whereas the transmission rate in 2010 was 4.5 per 100 person-years.
That said, the study also found that the vast majority of HIV transmissions occur when people with HIV are not engaged in clinical care. Of all U.S. transmissions in 2016, the study calculated that the 42.6% were from people who were aware of their HIV status but were not in care. Another 33.6% of transmissions were from people who were non-acutely infected and unaware of their status. The proportion of transmissions associated with people who were in care but not virally suppressed was 19.8%. Acutely infected people who were unaware of their status accounted for just 4% of transmissions.
Long-standing data show improved health outcomes when a newly diagnosed person starts antiretroviral therapy within six months of HIV infection. Routine testing and expanded testing options can allow people to be diagnosed sooner.
Errol Fields, M.D., Ph.D., M.P.H., with the Johns Hopkins University School of Medicine, said more must be done to address these gaps. "We still have a myriad of challenges with identifying people with unrecognized, undiagnosed infections," he said. "While the CDC has recommended universal, routine, opt-out screening for everyone age 13 to 64 for over 10 years, we in the medical community continue to fall short of that standard of care."
The new 2016 data come on the heels of Ending the HIV Epidemic: A Plan for America, the federal initiative proposed by the Department of Health and Human Services released last month. Its top four priorities are: diagnosing all people with HIV as early as possible after infection; achieving greater sustained viral suppression; expanding use of prevention interventions, including pre-exposure prophylaxis (PrEP); and enacting a quicker response to HIV outbreaks.
Eugene McCray, M.D., Director of the Division of HIV/AIDS Prevention at CDC, addressed the National HIV Prevention Conference in Atlanta this week, saying, "Harnessing the power of HIV treatment will be crucial to achieving the initiative's goals: reduce new HIV infections by 75% in 5 years and at least 90% in 10 years. Health care providers, public health departments, and other partners will play essential roles in meeting these targets."
Fields added, "Certainly, we need to do a better job at identifying and treating those with unrecognized HIV infection to reduce HIV transmission risk, but we also need to employ the other tools we have at our disposal to reduce HIV acquisition risk."
Increasing testing in accordance with improving outcomes in the continuum is a giant step toward ending this epidemic.
Stephen Hicks is a writer and public health advocate with a background in sexual health and harm reduction. He is based in Washington, D.C.