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Background: The risk of sexual HIV transmission increases when HIV viral load (VL) is above 1500 copies/mL. As such, persons newly diagnosed with HIV are at greater risk of transmission until they initiate ART and achieve sustained viral suppression. We sought to examine trends in time spent above three viral thresholds among persons newly diagnosed with HIV in San Francisco (SF).
Methods: We analyzed data from the HIV surveillance registry. Persons were included if they were diagnosed with HIV during 2008-2016, were SF resident at time of diagnosis, alive 12 months after HIV diagnosis and had ≥2 VL tests within 12 months after diagnosis. Consecutive VL pairs were used to calculate percent of person-time (pPT) spent above 200 copies/mL (pPT>200), 1500 copies/mL (pPT>1500) and 10000 copies/mL (pPT>10000) for the 12 months after HIV diagnosis. Multivariate zero-inflated negative binomial regression was used to assess trends in year of diagnosis and time spent above each viral threshold, while controlling for covariates (gender, transmission category, race/ethnicity, age, housing status, CD4+ lymphocyte count, health insurance type, and time from HIV diagnosis to ART initiation).
Results: Of the 3336 new HIV diagnoses from 2008-2016, 2556 (77%) met inclusion criteria for analysis. Overall, persons newly HIV diagnosed spent 53.6% of pPT>200, 44.1% pPT>1500, and 31.7% pPT>10000. By year, pPT>200 decreased from 70.3% in 2008 to 31.9% in 2016, pPT>1500 decreased from 62.3% in 2008 to 24.8% in 2016 and pPT>10000 decreased from 46.0% in 2008 to 17.0% in 2016 (p< 0.0001 for each threshold; see Figure). In adjusted regression, significant differences for all three pPT thresholds were found by transmission category, age, CD4 count, and time from HIV diagnosis to ART initiation. PWID (including MSM-PWID) and younger age were associated with increased pPT viremic. Persons with lower CD4 count and shorter time to ART initiation had decreased pPT viremic.
Conclusions: The percent time spent above each viremic level decreased significantly among newly diagnosed persons from 2008 to 2016. Thus, the possibility that persons with a recent HIV diagnosis could transmit HIV in more recent years decreased and likely contributed to the decreased HIV incidence observed in SF.


Percent time spent above each viral threshold during 12 months after HIV diagnosis by year of HIV diagnosis, San Francisco, CA, 2008-2016.
[Percent time spent above each viral threshold during 12 months after HIV diagnosis by year of HIV diagnosis, San Francisco, CA, 2008-2016. ]