SUMMARY: More widespread HIV testing and early antiretroviral therapy (ART) not only have clear benefits for the treated individual, but may also benefit the larger community by reducing the number of new HIV infections, according to 3 studies from North America presented at the 17th Conference on Retroviruses and Opportunistic Infections (CROI 2010) last month in San Francisco.

By Liz Highleyman

Effective ART that suppresses viral load to an undetectable level dramatically reduces the risk of forward HIV transmission. Mathematical models suggest that universal voluntary testing and widespread treatment -- either according to current guidelines or for everyone infected regardless of CD4 cell count -- could essentially halt the spread of the epidemic, but it is not yet clear how well this would work in the real world.

The 3 studies presented at CROI give the first indication that expanded testing and treatment are viable and can help reduce the spread of the disease in high-income countries with overall low prevalence (though specific areas may have pockets of high prevalence).

San Francisco

Moupali Das-Douglas (Photo by Liz Highleyman)

In the first study, Moupali Das-Douglas from the San Francisco Department of Public Health and colleagues looked at the effect of community viral load -- or viral load across an entire community -- on HIV incidence. They hypothesized that the recent decrease in community viral load in San Francisco would be associated with a reduction in new HIV infections.

The researchers used San Francisco's comprehensive HIV/AIDS surveillance system, which includes mandatory reporting of viral load data, as well as a CDC mathematical model of new infections to calculate community viral load, and to examine associations between community viral load and new HIV cases between 2004 and 2008.

They looked at 2 different measures of community viral load: total community viral load was defined as the sum of the most recent viral load measurements from all reported HIV+ individuals in a particular population. Mean community viral load was defined as the average of the most recent viral load measurements, that is, the sum divided by the number of people.

New HIV cases consist of 3 groups: people who received a new diagnosis of an existing HIV case (e.g., due to stepped-up testing capturing a backlog of previously infected but untested individuals), new reports of existing cases, and HIV incidence, or people who actually were recently infected. "We really don't have a very precise method of determining incidence," Das-Douglas noted.

Results

	After remaining stable at about 23,000-24,000 copies/mL during 2002-2005, mean community viral load started to fall, reaching 15,000 copies/mL in 2008, a 40% drop.
	This decline was associated with a significant decrease in new HIV cases, from 796 in 2004 to 434 in 2008, approaching a 50% decline.
	The number of people estimated to be infected but unaware of their status also fell considerably, from 24% to 15%.
	Estimated new or recent infections (according to the mathematical model) fell by about one-third between 2006 and 2008 (from 930 to 620 people), but this did not reach statistical significance.
	By the end of the study period, an estimated 80% of newly diagnosed people were linked to care, about 90% of these were on ART, and about 75% of treated people had achieved undetectable viral load.

"Increased antiretroviral treatment options and coverage, as well as increasing HIV status awareness," may have led to decreases in community viral load in San Francisco during the study period," the investigators concluded. "Findings support the hypothesis that wide-scale early ART can have a preventive effect at a population-level."

Because community viral load is "temporally upstream" of new HIV infections, public health departments should consider adding it to routine HIV surveillance to track the epidemic and evaluate the effectiveness of HIV prevention and treatment interventions, they suggested.

Speaking at an accompanying press conference, Das-Douglas described community viral load as a "virometer," or a way to take the temperature of a community. In response to a question, she noted that the decline in HIV cases occurred even as rates of other sexually transmitted infections rose, suggesting that people may be practicing serosorting (having sex only with partners of the same HIV status).

"This helps us see how well treatment is working, but also how well prevention is working, so can target interventions to those at highest risk," she said. "What gets measured gets managed."

Washington, DC

Amanda Castel from George Washington University School of Public Health and Health Services and colleagues reported findings from an analysis of the effect of increased testing in Washington, DC, which has the highest HIV/AIDS rate in the U.S. -- an estimated 3% overall seroprevalence.

In 2006, the DC Department of Health launched an initiative to promote routine HIV testing with improved linkage to care throughout the city (following the newly implemented CDC testing guidelines). This included opt-out testing at medical facilities, community campaigns to encourage testing, and testing and treatment in jails.

The researchers assessed trends in the number of HIV tests performed, the number of people treated, clinical indicators (CD4 cell count and HIV viral load) at the time of HIV diagnosis, and changes in numbers of new cases from 2004 to 2008.

Results

	The number of HIV tests performed annually rose dramatically, from about 20,000 in 2004, to 35,000 in 2006 at the start of the testing push, to 93,000 in 2009.
	The number of HIV diagnoses (according to name-based reporting) increased significantly, from about 1093 in 2004 to 1280 in 2007 (the last year with complete data), a decrease of 17%.
	Increased testing shortened the mean time between estimated date of infection and diagnosis.
	The percentage of people diagnosed with AIDS who did not learn their status until they developed advanced disease fell from 66% in 2004 to 57% in 2008.
	Median CD4 count at the time of diagnosis increased significantly, from 216 cells/mm3 in 2004 to 343 cells/mm3 in 2008, or by nearly 60%.
	The percentage of people who developed symptomatic AIDS within 1 year after diagnosis decreased from 47% in 2004 to 28% in 2008.
	The percentage of newly diagnosed individuals accessing care rose from about 75% in 2004 to about 95% in 2008.

"Expanded routine HIV testing in Washington, DC has been associated with increased identification of HIV/AIDS cases, more rapid entry into care as measured by time to initial CD4 count, percent or viral load, and earlier diagnosis as indicated by the initial CD4 count itself, and the decreasing proportion of late testers among AIDS cases," the researchers continued. "Continued surveillance will help determine whether these findings will translate into improved clinical outcomes and reduced HIV transmission."

Vancouver

Finally, Julio Montaner from the British Columbia Centre for Excellence in HIV/AIDS and colleagues looked the link between expanded ART coverage, community viral load, and decreased HIV transmission among injection drug users (IDUs) in the Downtown Eastside district of Vancouver, thought to be the area with the highest HIV/AIDS rate in Canada. The researchers provided results for the entire province of British Columbia, but overall rates largely reflect the situation in urban Vancouver.

ART (and medical services in general) are available free of charge for all British Columbia residents. A targeted effort to expand ART use among IDUs was started in 2007. HIV testing, ART distribution, and HIV viral load measurements in the province are centralized, allowing the researchers to obtain comprehensive data from administrative and medical records.

Results

	The number of HIV tests performed in British Columbia annually rose from 104,229 in 1994, to 137,980 in 1996 (the first years of the new program), to 182,151 in 2008.
	New HIV diagnoses in British Columbia dropped overall from 1996 to 2008, but the annual decrease plateaued in the early 2000s, before commencing a slower second decline, falling from 440 cases in 2004 to 370 in 2009.
	The rate of new diagnoses among IDUs specifically, however, continued to decline steeply, falling from 150 in 2004 to 80 in 2009.
	The number of people receiving ART doubled from about 2500 in 2000 to about 5000 in 2009.
	Average community viral load declined over the same period, with the proportion with > 50,000 copies/mL decreasing and the percentage with < 500 copies/mL increasing (from about 40% in 2004 to about 75% in 2009).
	Here, too, rates of other sexually transmitted infections increased even as HIV cases declined.

These findings, the researchers concluded, "demonstrate an association between expanded [ART] coverage, decreased provincial plasma viral load, and decreased new HIV diagnoses," which were temporally related to a treatment outreach effort targeting IDUs. Montaner suggested the decrease was likely due to more ART use rather than behavior change, since needle exchange and other harm reductions were widely implemented well before the decline began.

Taken together, while these studies cannot prove a causal link between increased testing, more widespread treatment, reduced community viral load, and the rate of new HIV infections, they do suggest that expanded access to testing and care is providing community-wide benefits.

Abstract 33: San Francisco Department of Public Health, San Francisco, CA; University of California, San Francisco, CA.

Abstract 34: George Washington University School of Public Health and Health Services, Washington, DC; HIV/AIDS Admin, District of Columbia Dept of Health, Washington, DC.

Abstract 88LB: British Columbia Centre for Excellence in HIV/AIDS, Vancouver, BC, Canada.

3/12/10

References

M Das-Douglas, P Chu, G-M Santos, and others. Decreases in Community Viral Load Are Associated with a Reduction in New HIV Diagnoses in San Francisco. 17th Conference on Retroviruses & Opportunistic Infections (CROI 2010). San Francisco. February 16-19, 2010. Abstract 33.

A Caste, R Samala, A Griffin, and others. Monitoring the Impact of Expanded HIV Testing in the District of Columbia Using Population-based HIV/AIDS Surveillance Data. 17th Conference on Retroviruses & Opportunistic Infections (CROI 2010). San Francisco. February 16-19, 2010. Abstract 34.

J Montaner, E Wood, T Kerr, and others. Association of Expanded HAART Coverage with a Decrease in New HIV Diagnoses, Particularly among Injection Drug Users in British Columbia, Canada. 17th Conference on Retroviruses & Opportunistic Infections (CROI 2010). San Francisco. February 16-19, 2010. Abstract 88LB.