Epidemiological Trends of Syphilis Infections in Japan and South Korea From 2011 to 2019

Background: This study aimed to investigate and compare the epidemiological trends of syphilis infections in Japan and South Korea from 2011 to 2019 and examine the factors contributing to the disparities in the incidence of syphilis between the two countries. Methods: A retrospective analysis was conducted using syphilis data from the National Institute of Infectious Diseases in Japan and the Korea Disease Control and Prevention Agency. Incidence rates were calculated and analyzed by gender and age group, with a focus on annual trends. Statistical analysis was performed using EZR (Easy R), and appropriate tests were conducted to evaluate the statistical significance of the results. Results: Japan experienced a substantial rise in syphilis cases, with an eight-fold increase (from 827 cases in 2011 to 7,007 in 2018) primarily among women aged 20 - 29 years (P < 0.05). In contrast, South Korea underwent a more modest increase, with a 1.82-fold rise in cases (from 965 in 2011 to 1,753 in 2019) predominantly among men aged 20 - 39 years (P < 0.05). The incidence rate in Japan increased by 8.09 times, while South Korea saw a 1.76-fold increase over the same period. In addition, Japan experienced an increase in congenital syphilis cases, whereas South Korea saw a decline. Conclusions: The contrasting syphilis trends in Japan and South Korea highlight the need for country-specific public health strategies. Japan’s sharp increase in syphilis cases, particularly among young women, necessitates an urgent reassessment of current preventive measures. In contrast, the relatively stable trend in South Korea suggests more effective disease management, although further investigation is needed to identify the contributing factors. These findings underscore the importance of tailored public health interventions to address the unique epidemiological challenges in each country.