Clinical Newswire February 17, 2010 (San Francisco, California USA)-
A decrease in community viral load was associated with a reduction in new HIV diagnoses in San Francisco, according to a presentation at the at the 17th Conference on Retroviruses and Opportunistic Infections (CROI) in San Francisco, California from 16-19 February 2010.*
Suppressing HIV viral load in individuals reduces perinatal transmission and may reduce sexual transmission of the virus. At the population level, it is unclear if reducing community viral load (CVL) has an effect on new HIV infections. Over the past several years there has been an increase in HIV testing and improvements in antiretroviral potency, tolerability, and treatment options. Dr. Mapouli Das and her colleagues hypothesized that reductions in San Francisco’s CVL would be associated with fewer HIV infections.
The researchers developed a measure of CVL, which, according to Dr. Das is like a virometer, a way to take the temperature of the community. “Knowing our community viral load not only tells us how well treatment is working at the community level but may also tell us how well HIV prevention interventions are working,” said Dr. Das.
San Francisco’s comprehensive HIV/AIDS surveillance registry was used to evaluate the CVL and new infections from 2004 to 2008. New HIV infections were determined from newly diagnosed and reported HIV cases and by using the Centers for Disease Control (CDC) incidence calculation methodology, a mathematical modeling approach that estimates the number of new HIV infections each year. Poisson models were used to evaluate the relationship between the annual total and mean CVL with new HIV diagnoses, virologic suppression, and CDC population-based point estimates.
The overall mean CVL for San Francisco was 23,348 copies. There were significant disparities in the mean CVL among African Americans, women, transgendered individuals, and injection drug users. There was a statistically significant reduction in total CVL from 2004 to 2008 (p=0.019) and a statistically significant correlation between total CVL and percent virologic suppression (p=0.002). Mean CVL also decreased from 2004 to 2008 (p=0.028), with a strong association between mean CVL reduction and reductions in newly diagnosed and reported HIV cases (p=0.005).
The CDC HIV incidence point estimates decreased 33% from 935 to 621. The relationship between the CVL during this time period with the point estimates treated as counts is highly statistically significant. However, when metaregression was used to properly account for the degree of imprecision in the point estimates the 33% reduction and its relationship with the CVL were not statistically significant. “So we are unable to reject the null hypothesis of no significance and we believe that is due to the imprecision of the imprecision of the CDC incidence calculation,” said Dr. Das.
Dr. Das concluded that in the past five years in San Francisco, testing rates and antiretroviral coverage increased, accompanied by a significant reduction in community viral load. Reductions in community viral load were significantly associated with a reduction in newly diagnosed and reported HIV cases. “We think this will be a helpful marker for health departments in evaluating outcomes, overall success of treatment and prevention interventions, and resource allocation and planning,” said Dr. Das.
*Das M, et al. Decreases in community viral load are associated with a reduction in new HIV diagnoses in San Francisco. CROI 2010. Oral Abstract Session 10, Abstract 33.
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