CROI 2011: Can Lowering Community Viral Load Decrease New HIV Infections?

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Decreased average and maximum community viral load (CVL) was associated with a decline in new HIV infections in San Francisco, and new HIV diagnoses are decreasing along with CVL in New York City, but this correlation has not yet been observed in Washington, DC, researchers reported at CROI 2011.

Starting antiretroviral therapy (ART) earlier appears beneficial for HIV positive individuals, but the public health effects of expanding treatment are not yet fully understood and remain a subject of controversy.

People on effective combination ART usually have low or undetectable viral load, and lower viral load dramatically reduces the likelihood of transmitting the virus during sex or injection drug use.

The recent 18th Conference on Retroviruses and Opportunistic Infections (CROI 2011) in Boston featured a poster discussion session devoted to community viral load -- or the average viral load in a population -- and its effects on local HIV/AIDS epidemics.

"Community viral load is an attempt to monitor the health of a community as individual viral load does for an individual," moderator Susan Buchbinder from the San Francisco Department of Public Health (DPH) said at a CROI press conference discussing the findings.

San Francisco

Moupali Das from the San Francisco DPH and colleagues used active case surveillance data from San Francisco's comprehensive HIV/AIDS case registry to assess trends in mean CD4 cell count at diagnosis, ART initiation, viral load, and time to virological suppression.

San Francisco has one of the most aggressive programs of HIV testing and linkage to care among U.S. cities. As previously reported, San Francisco General Hospital and the DPH last year adopted a policy of offering ART to everyone diagnosed with HIV, regardless of CD4 T-cell count.

The researchers estimated community viral load in 4 ways: the averages of the most recent, minimum, and maximum viral load for all cases in the past year, and log transformation of the mean of the most recent viral load. They then assessed the relationship of these CVL measures and newly diagnosed and reported HIV cases.

HIV positive people in San Francisco are generally diagnosed early compared with other cities. The mean CD4 count at the time of diagnosis remained consistently > 400 cells/mm3, while mean CD4 count at the time of ART initiation increased from about 350 to nearly 450 cells/mm3 between 2007 and 2009.
Das said there were "dramatic improvement in all markers" during the study period. Most recent, minimum, and maximum CVL all declined significantly between 2004 to 2009, and were significantly associated with decreases in the number of both newly diagnosed and newly reported HIV cases.

The most recent average CVL fell from about 25,000 copies/mL in 2004 to about 10,000 copies/mL in 2009, while the number of new HIV diagnoses decreased from 820 to 500 during the same period. Furthermore, the time from HIV diagnosis to virological suppression decreased from 32 months in 2004 to 5 months in 2009, with time from ART initiation to viral suppression falling from about 19 months in 2004 to 3 months in 2009.

Based on these findings, the researchers concluded, "Since 2004 and substantially in the last year, there have been notable gains in San Francisco's efforts to offer individuals earlier treatment and reduce time to virologic suppression, which has been associated with reductions in the community viral load and correlates with decreased newly diagnosed and reported HIV cases."

Das attributed these changes to expanded HIV testing, more frequent testing, and more formalized linkage to care programs, as well as "tremendous gains" in ART effectiveness during this time period that have enabled viral suppression in people who were not previously suppressed.

New York

Fabienne Laraque and colleagues from the New York City Department of Health and Mental Hygiene evaluated community viral load as a population-level marker to monitor the impact of interventions to control HIV.

This analysis included HIV positive city residents reported to the NYC HIV Registry who were alive at the end of 2008 and had at least 1 viral load measurement reported as of December 31, 2009. CVL was defined as the mean of individual viral load averages reported between January and December 2008.

New York City's CVL in 2008 was approximately 20,000 copies/mL overall, and approached 45,000 copies/mL among people with detectable viral load (> 400 copies/mL). But CVL varied significantly according to demographic characteristics, clinical characteristics, and neighborhood. Men, young and middle-aged adults, men who have sex with men, people with AIDS, individuals with low CD4 count, and people diagnosed after 2006 had higher mean viral loads.

Overall, about 55% of HIV positive people achieved virological suppression, again varying widely according to individual and neighborhood characteristics. Whites and Asians and people older than 30 years were more likely to have undetectable viral load.

"Community viral load can be utilized to target interventions aimed at groups and neighborhoods with higher community viral load and to track the impact of HIV control interventions," the investigators concluded.

CVL is a useful public health outcome measure, but can be politically tricky, Laraque said at the CROI press conference. "We must target [people who most need care] but not point fingers," she emphasized. "The positive spin is that there's something we can do."

Washington, DC

Finally, Amanda Castel from George Washington University School of Public Health and Health Services and colleagues assessed trends in CVL in Washington, DC, which has one of the highest HIV/AIDS rates in the U.S.

The researchers analyzed data on all prevalent HIV/AIDS cases diagnosed and reported to the DC HIV/AIDS surveillance database between 2004 and 2008. The most recent viral load for each individual was used to calculate average and total CVL.

About half of the more than 15,500 people diagnosed with HIV/AIDS between 2004 and 2008 had at least 1 available viral load measurement. The average CVL among this subset using the most recent viral load was nearly 56,000 copies/mL, while the total CVL was more than 422,000,000 copies/mL. During the 5-year study period, total CVL significantly increased, but mean CVL significantly declined. To date, however, this has not been associated with falling HIV incidence.

The average of the most recent viral load measurements was highest for women, blacks, and people infected via heterosexual sex, injection drug use, or "other" modes of transmission. The highest mean CVL was observed in areas with the highest levels of poverty and unemployment, and the lowest proportion of high school graduates.

"Mean and total community viral load, as markers of access to care and treatment, and indicators of the viral burden in the population, are useful in assessing trends in local HIV/AIDS epidemics," the researchers concluded. "This methodology may serve as a novel tool for assessing the potential impact of HIV prevention interventions at a population level."

Investigator affiliations:

Abstract 1022: San Francisco Dept of Public Health, San Francisco, CA; Univ of California, San Francisco, CA.

Abstract 1024: New York City Dept of Health and Mental Hygiene, New York, NY.

Abstract 1023: George Washington Univ School of Public Health and Health Services, Washington, DC; HIV/AIDS, Hepatitis, STD, and TB Admin, District of Columbia Dept of Health, Washington, DC.

4/19/11

References

M Das, P Chu, G-M Santos, et al. Success of Test and Treat in San Francisco? Reduced Time to Virologic Suppression, Decreased Community Viral Load, and Fewer New HIV Infections, 2004 to 2009. 18th Conference on Retroviruses and Opportunistic Infections (CROI 2011). Boston. February 27-March 2, 2011. Abstract 1022.

F Laraque, H Mavronicolas, H Gortakowski, and A Terzian. Disparities in Community Viral Load among HIV-infected Persons in New York City
18th Conference on Retroviruses and Opportunistic Infections (CROI 2011). Boston. February 27-March 2, 2011. Abstract 1024.

A Castel, M Befus, T West-Ojo, et al. Community Viral Load as a Population-based Biomarker of HIV, Washington, DC, 2004 to 2008. 18th Conference on Retroviruses and Opportunistic Infections (CROI 2011). Boston. February 27-March 2, 2011. Abstract 1023.