Syphilis in people living with HIV does not account for the syphilis resurgence in Japan

Abstract

Objectives: This study aimed to determine whether the current syphilis resurgence in Japan is attributable to incident syphilis in people living with HIV (PLWH).

Methods: This observational, retrospective, population-based study used data from the Japanese National Database. Data were extracted for PLWH who received antiretroviral treatment between January 2009 and December 2018. Using these data, along with the annual number of PLWH and syphilis diagnoses in the total population of Japan acquired from the National Institute of Infectious Diseases, the fraction of PLWH with syphilis compared to the total number of syphilis patients reported each year was calculated.

Results: There was a dramatic increase in syphilis cases during the study period. However, the incidence of syphilis in PLWH was stable during 2010-2018; the fraction of PLWH with newly diagnosed syphilis remaining at approximately 2% of the total PLWH cases in Japan each year. The proportion of newly diagnosed syphilis cases in PLWH decreased during the study period and accounted for <10% of the total syphilis cases in Japan since 2016 (14.9% in 2015 to 9.5% in 2016 and 5.9% in 2018). An increasing trend in the number of newly diagnosed syphilis cases in PLWH aged >50 years was observed (7.4% in 2010 to 10.4% in 2014 and 14.9% in 2018).

Conclusions: The recent dramatic increase in syphilis cases in Japan was not seen in PLWH. Thus, the resurgence of syphilis in Japan cannot be attributed to its transmission in the PLWH population.

Keywords: Administrative claims database; HIV; National Database of Health Insurance claims of Japan; Population-based study; Sexually transmitted diseases; Syphilis diagnosis.