Our study found that the PVL indicator value in Xinjiang, China, was consistent with the changing trend of the PVL indicator value in cities in other countries, showing a decreasing state from year to year[23, 24] in the time-based longitudinal analysis. Although the PVL surrogate indicators MVL, ICVL, AVL, CVL, total VL, mean VL, and geometric mean VL showed the same trend of change in new HIV infection rate, only CVL was positively associated with new HIV infection rate. In correlation analyses with ART coverage, viral unsuppression rate, and viremia prevalence, new HIV incidence was significantly correlated with ART coverage, viral unsuppression rate, and mean CVL, geometric mean CVL, and mean ICVL were also strongly correlated with ART coverage and viral unsuppression rate.
Taken together, mean CVL and geometric mean CVL are better as surrogate indicators of PVL to measure the HIV transmission potential and HIV disease burden in Xinjiang population. This is consistent with the findings of India[14], South Carolina[24], Rhode Island[25], and validates the former hypothesis that as ART coverage increases, viral unsuppression rate decrease, CVL decreases, and new HIV infection rate decrease. But the difference is that other indicators of PVL in Solomon's[14] study also correlated with new HIV infection rate, which is slightly lower than that of CVL. However, this study showed no significant association between MVL, ICVL, and AVL and new HIV infection rate, ART coverage, or viral unsuppression rate. This may be related to the included population size of different PVL indicators in this study. The present study MVL largely coincided with the inclusion population (on treated) of ICVL, who had a predominance of VL suppressed and VL undetectable individuals, a low population VL base, and a relatively slow VL decline trend over the 3-year period. In previous studies[14, 18, 26], MVL and ICVL monitoring in the treated population VL, the easy observation of personnel, and the strong availability of data allowed the study of MVL and ICVL as surrogate indicators to predominate[11]. However, a limitation is that both are not included in the confirmed but untreated cohort, and the workhorse of HIV transmission[27]- the high VL population is mostly concentrated in this group, thus prone to low estimated PVL. AVL covers a portion of the untreated population on the basis of MVL and ICVL, but population coverage remains incomplete, and not all diagnosed persons are aware of their VL condition. We found that the CVL values in 2017–2019 in Yining City were higher than those of MVL, ICVL, and AVL, compared with other indicators. CVL is a more comprehensive and representative estimate of PVL, encompassing all populations in whom PVL can be monitored (those who are undiagnosed cannot be monitored), including untreatment individuals. This is in agreement with the US CDC guidelines for CVL[11], the studies by Rozhnova[28] and Farahani[29]. Therefore, we believe that CVL is a better monitor and indicator of the HIV transmission potential and disease burden in the population than other surrogate markers of PVL.
Expanding VL surveillance, making full use of VL information, and achieving the cross from individual VL to population VL, transformed PVL from an observational epidemic domain to an indicator for rapid action to improve HIV disease burden[27]. Based on the above results, we choose mean CVL and geometric mean CVL to quantify the HIV burden of the population in Yining, Xinjiang, China, to find the HIV hotspot populations in different characteristic populations. Among them, CVL was relatively high in male, ≤ 25 years old, Primary school and below, other household registration place, other medicare types, other sample sources, non-married commercial heterosexual contacts and non-married commercial heterosexual contacts. Targeted interventions should be implemented with respect to their characteristics, with the aim of highly effective reduction of the HIV disease burden in the population.
Viremia prevalence adjusted for the amount of HIV negative persons in the study observations was also suggested by Solomon[14] to be a better indicator of HIV transmission potential. However, we only found that there was an association between total CVL and the prevalence of viremia, while there was no significant association between total CVL and the prevalence of new HIV infection, and there was no significant association between total CVL and art coverage, virus uninhibited rate, the results suggest caution when using this indicator to monitor the HIV burden in communities in Xinjiang, China. In addition, it is important to note that limit of VL values for the prevalence of viremia varied among studies, such as 20 copies/mL which we chose, and 150 copies/mL in the study by Patel[30]. Sensitivity analysis of its values can be considered in future studies to explore whether the results differ at different limit of VL values in the same sample.
In the geographical community analysis of the distribution of indicators related to the burden of HIV disease and the effect of HIV prevention and treatment in each community, it is intuitive to find the "hotspot communities" that need to be focused on, accurately locate the high CVL community, and measure the HIV epidemic status in the city. HIV hotspot communities are an important area for large-scale intervention in the future[31], hotspot communities will shape the environment of high-risk groups for HIV-negative people in the region, increase their risk of infection, and those living in hotspot communities with a longer history of HIV have the potential for sustained HIV transmission[32], which is easy to form the source of continuous transmission of HIV[33]. This study supports the combination of geospatial analysis to shift the research objects from individuals to key populations and hotspot communities, combine the regional characteristics of spatial characteristics, use CVL to accurately locate hotspot communities and highly detected populations, and expand HIV testing for communities and populations with high CVL, in order to discover more and more complete new reports and new infections, and achieve efficient epidemic tracking. Integrating geospatial analysis into routine public health planning will help focus interventions on more precise geographical units for maximum epidemiological impact and effective resource allocation, while more nuanced assessment of the effectiveness of HIV responses.
Several limitations should be noted. First, the HIV transmission potential was analyzed without taking into account the impact of HIV prevalence and behavior in the population. As in different populations with the same CVL, those with higher HIV prevalence and incidence of high-risk behaviours necessarily have higher HIV transmission potential[13]. Based on this, we analyzed the CVL of different characteristic populations. Second, in the time-based longitudinal analysis, the study period is shorter, the trend of viremia prevalence is subtle, and the trend of longer follow-up time may be more significant, considering these factors, extending the follow-up time in future CVL studies, and effectively combining HIV prevalence and high-risk behaviors, the results will be more stable and more critical, and more conducive to analyzing the HIV epidemic and prevention and treatment effects from the population level, achieving accurate prevention and control, and matching resources and needs.
In conclusion, our results show that mean CVL and geometric mean CVL can be better substitutes for PVL, and affirm the utility of CVL as an indicator of HIV transmission potential through time and geography, and can cooperate with ART coverage, viral unsuppression rate, viremia prevalence and other indicators to dynamically monitor the HIV epidemic and evaluate the effect of HIV prevention and treatment in Yining City. At present, the overall CVL in Yining City has decreased year by year, affirming the current prevention and control efforts, which should expand the scope of VL detection in the future, better apply CVL, and monitor the local HIV transmission potential. Combined with spatial geography to accurately locate hot communities and high-detection populations of HIV, and carry out prevention and treatment work more accurately and rapidly, it provides new, efficient and practical monitoring indicators and indicators for reasonable allocation of health resources to the health department.