Background: Zimbabwe estimated a decline in HIV incidence from 4.6% (1993) to 0.88% (2015) using Spectrum model. The country has made significant investments in HIV prevention, care and treatment in the last decade. Zimbabwe conducted a Population-Based HIV Impact Assessment (PHIA) that measured HIV incidence in 2015/16.
Methods: A total 22,496 adults (15-645 years) consented to both a face-face questionnaire and biomarker testing in the nationally-representative household survey which had 83.9% response. Home-based HIV testing was performed using the national serial rapid test algorithm of Determineä, First Responseä and Stat-Pak (tie-breaker). HIV positives were confirmed in a satellite laboratory using Geenius HIV-1/2ä, viral load using Roche Taqman and Biomerieux nuclisens and recency using Limiting Antigen Avidityä (LAg). Recent was confirmed by an algorithm of LAg normalized optical density < 1.5 + viral load >1000 copies. We calculated weighted annual HIV incidence.
Results: Overall, 36 of 3,503-(1.03%) HIV positive cases were confirmed as recent infection. Among these, 11 were male and 25 female. The weighted annual incidence was 0.45% (95% CI 0.28 -0.62) and 0.48% (0.29-0.66) for adults 15-64years and 15-49years respectively. The observed incidence (0.48%) is nearly half that reported by Spectrum (0.88%) The point-estimate for incidence was more than twice as high among women (0.67% [0.37-0.97]) compared to men (0.28% [0.06-0.50]) in the 15-49 year age-group. Young men (15-24 years) had lowest incidence, 0.13% (0.00-0.34), while it was three-times high (0.54% [0.14 - 0.94]) in women of similar age-group. By residence, overall incidence for adults (15-49 years) was higher in urban, 0.63% (0.25-1.01) compared to 0.38% (0.18-0.59) in rural setting. The majority of respondents (15-49 years) with incident infections (26/31, 83.9%) had previously been tested. The point-estimate among those ever tested was 0.56% (0.32 -0.80) compared to 0.25% (0.00 -0.52) for participants without prior HIV testing.
Conclusions: HIV incidence remains high among women especially in young women. The high incidence in urban setting may be a signal for increase in high risk behaviours and emergence of sub-epidemics. High incidence among previously tested cases suggest the need to strengthen prevention messaging. Additional exploration, focused interventions should be prioritized.