A study linking declines in the average viral load in San
Francisco communities with reduced HIV incidence was published in PLoS One last
month. The lead author, Moupali
Das-Douglas, presented the paper at CROI in February where it attracted some coverage,
but the publication in PLoS appears to have flown beneath the media radar. The
authors are careful to acknowledge that their data are associative, stating: “this
is an observational study and there is limited ability to directly assess
causality.” However, they argue that tracking viral loads at the community
level can be a valuable health indicator, revealing disparities in access to
healthcare services that need
to be addressed. The authors also note that the documented decline in HIV
infections occurred despite increases in other STDS, such as rectal gonorrhea, bolstering
the case that viral load reductions rather than changes in risk behavior
account for the findings.
The webcast of Moupali Das-Douglas’s CROI presentation is available
on the conference website.
PLoS One. 2010 Jun 10;5(6):e11068.
Das M, Chu PL, Santos GM, Scheer S, Vittinghoff E, McFarland
W, Colfax GN.
San Francisco Department of Public Health, San Francisco,
California, USA.
Abstract
BACKGROUND: At the individual level, higher HIV viral load
predicts sexual transmission risk. We evaluated San Francisco's community viral
load (CVL) as a population level marker of HIV transmission risk. We
hypothesized that the decrease in CVL in San Francisco from 2004-2008,
corresponding with increased rates of HIV testing, antiretroviral therapy (ART)
coverage and effectiveness, and population-level virologic suppression, would
be associated with a reduction in new HIV infections. METHODOLOGY/PRINCIPAL
FINDINGS: We used San Francisco's HIV/AIDS surveillance system to examine the
trends in CVL. Mean CVL was calculated as the mean of the most recent viral
load of all reported HIV-positive individuals in a particular community. Total
CVL was defined as the sum of the most recent viral loads of all HIV-positive
individuals in a particular community. We used Poisson models with robust
standard errors to assess the relationships between the mean and total CVL and
the primary outcome: annual numbers of newly diagnosed HIV cases. Both mean and
total CVL decreased from 2004-2008 and were accompanied by decreases in new HIV
diagnoses from 798 (2004) to 434 (2008). The mean (p = 0.003) and total CVL (p
= 0.002) were significantly associated with new HIV cases from 2004-2008.
CONCLUSIONS/SIGNIFICANCE: Reductions in CVL are associated with decreased HIV
infections. Results suggest that wide-scale ART could reduce HIV transmission
at the population level. Because CVL is temporally upstream of new HIV
infections, jurisdictions should consider adding CVL to routine HIV
surveillance to track the epidemic, allocate resources, and to evaluate the
effectiveness of HIV prevention and treatment efforts.
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