Characterising the rate of syphilis diagnosis among people incarcerated in state-level prisons: a cohort study in Washington state 2013-2023.

OBJECTIVE

The syphilis epidemic in the USA has expanded dramatically into new populations, but the overlap with prison populations is unknown. The objective of this analysis was to describe trends in syphilis diagnosis among people incarcerated and released from a state prison system.

METHODS

This was a cohort study of people released from prison in Washington state between 2010 and 2022. Linking prison rosters to Washington surveillance data, we calculated the rate of syphilis diagnosis between 2013 and 2023 when individuals were inside and outside of prison and compared it to the general population of Washington state.

FINDINGS: The rate of syphilis diagnosis increased substantially both in prison (36 per 100 000 person-years in 2013 to 274 in 2022, rate ratio vs general population 1.3 in 2013 to 2.1 in 2023) and out of prison (8 in 2013 to 887 in 2023, rate ratio vs general population 0.3 in 2013 to 6.4 in 2023) over time.

INTERPRETATION: From 2013 to 2023, the rate of syphilis diagnosis among those incarcerated in prison in Washington changed from similar to the general population to being significantly greater. Opt-out syphilis testing and treatment in prisons should be included in prison guidelines and accreditation standards.