More people with HIV are achieving viral suppression in US, but about 40% remain above transmission thresholds

A growing proportion of people with HIV are reaching an undetectable viral load on antiretroviral therapy (ART), according to a pair of studies from the US Centers for Disease Control and Prevention presented at the Conference on Retroviruses and Opportunistic Infections (CROI 2016) last month in Boston. Despite this improvement, however, a substantial number of people are still not achieving viral suppression, putting them at risk for disease progression and onward transmission of the virus.

Experts have developed the 'continuum of care' concept to characterise how people with HIV progress through the steps of diagnosis, linkage to care, starting ART and achieving viral suppression. In 2014 the CDC reported that while 86% of the estimated 1.2 million people living with HIV in the US in 2011 had been diagnosed, just 40% were engaged in HIV medical care and only 30% had achieved undetectable viral load.

Medical Monitoring Project

Heather Bradley and colleagues from the CDC used data from the national Medical Monitoring Project (MMP) during 2009-2013 to estimate the proportion of people receiving HIV medical care in the US who achieved viral suppression (< 200 copies/ml) at both their last test and all tests in the previous 12 months.

The researchers collected data from 23,125 people with HIV using interviews and medical record abstractions. They assessed trends over time in viral suppression overall and by sex, age, race/ethnicity and sexual behaviour/orientation.

The proportion of people with viral suppression at their most recent test rose steadily from 72% in 2009 to 80% in 2013. This upward trend was statistically significant for both men and women, for all age groups, for white, black and Hispanic people, and for gay/bisexual men and heterosexual men and women.

Large increases in viral suppression were seen in the 18-29 age group (rising from 56% in 2009 to 68% in 2013), the 30-39 age group (from 62% to 75%), African Americans (from 64% to 76%), women (from 66% to 77%) and men who have sex with men (from 76% to 82%).

Similarly, the proportion of people whose HIV was consistently suppressed on all tests during the previous 12 months increased steadily from 58% in 2009 to 68% in 2013. Again, the rising trend was significant for all sex, age, race/ethnicity and sexual behaviour/orientation groups.

Big increases in consistent viral suppression were seen in the same groups: age 18-29 (from 32% to 51%), age 30-39 (from 47% to 63%), black people (from 49% to 61%), women (from 52% to 64%) and men who have sex with men (from 61% to 71%).

Not surprisingly, increases in viral suppression reflected that a growing proportion of HIV-positive people in care were being prescribed ART, up from 89% in 2009 to 94% in 2013. But even after adjusting for rising prescription rates, increases in the proportion of people with undetectable viral load remained significant for most subgroups.

"Viral suppression increased significantly among adults in HIV medical care in the United States," the researchers concluded, with the "largest increases among subgroups with lowest levels of viral suppression in 2009".

"Enhanced efforts [are] needed to address social and behavioural factors affecting attainment of viral suppression," they added, including further reduction in medication burden and dosing frequency and increased access to supportive services.

Factors that may have contributed to greater viral suppression include broader guidelines recommending treatment for more – and eventually all – people with HIV, elimination of AIDS Drug Assistance Program (ADAP) waiting lists and ongoing improvements in the potency and tolerability of antiretroviral drugs.

"These findings are really encouraging in terms of improving the health of people living with HIV and preventing infection," Bradley said at a CROI press conference.

She noted, however, that these encouraging numbers are not directly comparable to those in the CDC's widely cited 2011 cascade of care report, as they refer to the proportion of HIV-positive people in medical care – not all people living with HIV – who have achieved viral suppression.

National HIV Surveillance System

As described in a related poster presentation, Nicole Crepaz of the CDC's Division of HIV/AIDS Prevention and colleagues looked at data from the National HIV Surveillance System (NHSS) to assess viral burden among people aged 13 and older who received an HIV diagnosis before 2011 and were still alive through 2013.

The analysis included data from people in 17 jurisdictions (16 states and Washington, DC) that reported CD4 cell count and viral load results to the NHSS. Three-quarters were men, 38% were black, 31% were white and 25% were Hispanic. Over half (56%) were men who have sex with men, 11% were people who inject drugs, and 12% were women and 5% were men exposed through heterosexual contact.

Of the 265,264 people with HIV in these jurisdictions who were engaged in care and had at least one viral load test in 2011, a total of 238,614 (95%) had at least two further viral load tests during 2012-2013. However, 14% had a gap of more than 12 months between tests.

Of the 238,641 people with at least two subsequent tests, 62% had durably suppressed viral load, or undetectable levels on all measurements. Men were more likely to have durable viral suppression than women (64% vs 55%), white people were more likely than Hispanic or black people (73%, 61% and 53%, respectively), and older age groups were more likely than younger ones (72% for > 55 years, 59% for 35-44 years, 38% for 13-24 years).

Among the 91,120 people (38%) without durably suppressed viral load, the mean number of days spent above 200 copies/ml was 438 – 60% of the two-year observation period. Further, an average of 316 days (about 40% of the period) were spent with a viral load above 1500 copies/ml and 215 days (about 30%) above 10,000, indicating a substantial risk of onward transmission.

Women, African Americans and young people had substantially higher mean viremia 'copy-years' and more days with viral load above 200, 1500 or 10,000 copies/ml. Gay men spent the least time with viral load under any of these thresholds. People with more than a 12-month gap between tests spent more time with elevated viral load (mean 337 days).

The researchers concluded that it is "encouraging" that nearly two-thirds of HIV-diagnosed people in care had suppressed viral load over a two-year period.

However, "persons without durable viral suppression spent an average of 60% of [the] two-year time with viral load above 200 copies/ml as well as a considerable length of time above 1500 or 10,000 copies/ml that considerably increase[s] the risk of transmitting HIV infection," they cautioned. "The high proportion of time these individuals spent above transmission risk thresholds raises concern because they were not isolated blips of viremia, but rather extended periods of many months of elevated transmission risk potential."

"Viral burden was higher among populations known from previous research to have suboptimal engagement in HIV-related medical care," they added. "Tailored care and treatment efforts are needed to address disparity in viral suppression."