Mean HIV viral load among resident cases and the undiagnosed in Oregon

Background: Community viral load estimates do not account for undiagnosed HIV, which comprises 20% of the infected population. We estimated mean viral load (MVL) (the population viral load) for all living HIV-infected Oregon residents aged ≥13 years, including those undiagnosed.

Methods: We determined the number of resident cases from address at last lab report; we estimated undiagnosed cases as 20.1% of living cases. We selected the last viral load during the prior 1.5 years for resident cases and, for the undiagnosed, used the mean of first viral load results following diagnosis (2006-2011). We calculated z-scores to compare group differences in geometric mean.

Results: We estimated that 6,986 people with HIV lived in Oregon during August 2011, including 5,582 resident cases and 1,404 undiagnosed. MVL among resident cases and those undiagnosed was 6,884 copies/mL. MVL among resident cases was 92 copies/mL, 80% of whom had viral loads ≤200 copies/mL. We estimated the 1,404 undiagnosed had a MVL of 33,884 copies/mL. Resident cases with higher MVLs were more likely to be African American than white (p<0.001), less likely to have AIDS (p<0.001), and more likely to be injection drug users (IDU) vs. men who have had sex with men (MSM) (MSM/IDU p=0.001; IDU p=0.037). MVL was highest among 20-24 year-olds, decreasing with age. Higher MVLs among the undiagnosed were found among males (p=0.001), those with AIDS (p<0.001), and male IDU vs. MSM (p=0.001).

Conclusion: Including estimates for the undiagnosed increased Oregon's MVL 74-fold and provides a more realistic index of community-wide risk.