Estimates of the number of people living with undiagnosed HIV in the UK, released yesterday in Public Health England (PHE)’s annual report (https://www.gov.uk/government/publications/hiv-in-the-united-kingdom), indicate that the UK has become one of the first few countries in the world to have reached the UN’s 90-90-90 targets, i.e. that at least 90% of people living with HIV (PLWH) should be diagnosed; 90% of those diagnosed should be on treatment; and 90% of those on treatment should have viral suppression. In 2017, 92% (credible interval CrI 88-94%) of the estimated 101,600 (CrI 99,300-106,400) PLWH were diagnosed; 98% of diagnosed PLWH were observed to be receiving treatment; and 97% of those on treatment were virally suppressed.

These estimates are reflective of a steady progression towards reaching the 90-90-90 targets over the last decade, and are supported by an estimated decline in HIV incidence in gay, bisexual and other men who have sex with men (MSM), from a peak of 2,700 (CrI 2,200-3,200) new infections in 2012 to 1,200 (CrI 600-2,100) in 2017.

These important estimates of both the numbers undiagnosed and the numbers of incident infections are based on models developed by Dr Daniela De Angelis’ group here at the MRC Biostatistics Unit. A Bayesian multi-parameter evidence synthesis that combines various surveillance and other survey data to estimate the prevalence of HIV, both diagnosed and undiagnosed, has formed the basis of PHE’s annual assessment of the state of the epidemic in the UK since 2005. In more recent years, PHE have also adopted a Bayesian back-calculation approach developed by Dr De Angelis’ group, based on a multi-state model of disease progression towards the clinical endpoint of HIV diagnosis, to estimate HIV incidence in MSM.