Trends in advanced HIV disease, treatment interruption, and viraemia in KwaZulu-Natal, South Africa.

Advanced HIV disease (AHD), treatment interruption and viraemia remain key challenges to effectiveness of HIV programmes in South Africa. Understanding the trends of these measures and their variation across geographic regions can inform more targeted and responsive interventions. We conducted a retrospective cohort study using routine, de-identified data from TIER.Net, a national HIV electronic register. We curated data from 116 primary care clinics in eThekwini, uMgungudlovu, and uMkhanyakude Districts in KwaZulu-Natal province. We included people living with HIV aged [≥]16 years, who initiated or collected ART between 1 July 2018 and 30 June 2023. We examined trends in annual proportion of AHD, treatment interruption and viraemia, and mapped the clinic-level proportions of these outcomes using inverse distance weighted interpolation maps. Among 123,473 clients initiating ART with CD4 count measurements, the overall prevalence of AHD remained stable over the period (20.0%-22.2%). There was an overall decline in treatment interruptions from 13.2% to 11.3% among the 544,066 clients who had scheduled visits. Of the 446,899 clients who had viral load results, overall viraemia [≥]50 copies/mL increased from 12.9% to 20.2%, whereas viraemia [≥]1000 copies/mL remained stable at approximately 6%. Spatial analyses highlighted geographic disparities in AHD, treatment interruption, and viraemia across and within the districts. While declines in treatment interruptions are promising, the persistence of AHD and viraemia ([≥]50 copies/mL) require further investigation and highlight ongoing challenges for HIV control. The observed spatial variation across districts underscores the need of geographically tailored interventions to strengthen programmatic effectiveness, particularly in hyper-endemic settings like KwaZulu-Natal.