[Estimation of newly HIV infection trend by using the back-calculation method in Honghe Hani and Yi autonomous...

Objective: Using the changing patterns of CD(4)(+) lymphocytes (CD(4)) counts of HIV/AIDS cases, we tried to estimate the number of newly infected HIV in Honghe Hani and Yi autonomous prefecture (Honghe prefecture) Yunnan province, and to provide reference for evaluating the trend of local HIV epidemic. Methods: Among diagnosed HIV infections, those who were at ≥15 years old, having available initial CD(4) records of testing, initiating antiviral therapy before the end of 2018, were selected from the case reporting system of Honghe prefecture, Yunnan province. Both Depletion model of the square root on CD(4) and the time of infection were used to back-calculate the seroconversion time of each individual. Both direct probability distribution method and life table method were used to calculate the distribution rates of diagnosis and the weight of delay. The number of diagnoses over the years was used to reversely estimate the total number of newly HIV infections. Results: At the end of 2018, the total number of HIV infections was estimated 35 977 with the rate of diagnosis as 77.50% in Honghe prefecture of Yunnan province. The number of new HIV infections appeared as 23 792 in 2008-2018. Cumulatively, the number of new HIV infections was 12 185 up to 2007. The estimated number of new HIV infections decreased from 2 602 in 2008 to 1 480 in 2018. The weight of diagnostic delay decreased from 5.49 in one year to 1.00 in 20 years, and the diagnosis rate increased from 18.2% to 100.0% during 20 years. Conclusion: In Honghe prefecture of Yunnan province, the number of newly infection showed a declining trend but the diagnostic rate was still far from reaching the "first 90% target" . It is expected to expand the timeliness on detection and case-finding so as to reduce the risk of HIV transmission.