Decreases in community viral load are accompanied by reductions in new HIV infections in San Francisco

• Published in: PloS one Vol. 5; no. 6; p. e11068
• Main Authors: Das, Moupali, Chu, Priscilla Lee, Santos, Glenn-Milo, Scheer, Susan, Vittinghoff, Eric, McFarland, Willi, Colfax, Grant N
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 10-06-2010; Public Library of Science (PLoS)
• Subjects: Acquired immune deficiency syndrome; AIDS; Analysis; Antiretroviral agents; Antiretroviral drugs; Antiretroviral therapy; Biological products industry; Chronic illnesses; Communities; Disease prevention; Disease transmission; Drug therapy; Epidemics; Evaluation; Health risks; Highly active antiretroviral therapy; HIV; HIV infections; HIV Infections - epidemiology; HIV Infections - virology; HIV tests; Human immunodeficiency virus; Human subjects; Humans; Hypotheses; Infections; Infectious Diseases/HIV Infection and AIDS; Medical diagnosis; Medical tests; Population; Population Surveillance; Public health; Public Health and Epidemiology/Epidemiology; Public Health and Epidemiology/Infectious Diseases; San Francisco - epidemiology; Sexual transmission; Studies; Surveillance; Tuberculosis; Viral Load; San Francisco; United States > US; San Francisco California; California
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0011068

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.
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.
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.