Tokyo's Syphilis Epidemic Related to Sex Industry

Japan has experienced a dramatic resurgence of syphilis since 2010, reaching epidemic rates again in 2025.

The Japan National Institute of Infectious Diseases (NIID) has reported a significant increase in syphilis cases over the past decade, with the last four years averaging over 13,000 cases annually.

In 2025, the NIID confirmed that this unfortunate trend continued for the fourth consecutive year.

Among Japan's prefectures, Tokyo accounted for 25% of the national total of syphilis cases, followed by Osaka, Aichi, Fukuoka, and Kanagawa.

According to a December 2025 analysis, syphilis risk factors among predominantly heterosexual populations in urban Japan have significantly increased. These findings reveal that casual sexual partnerships and diverse sexual networks facilitated by dating applications and commercial sex services create unique transmission dynamics not adequately captured by previous research.

These researchers stated that promoting preventive measures among sex industry workers and patrons is crucial in Japan's cities.

Syphilis is a sexually transmitted infection (STI) that is generally transmitted by contact with infectious sores, through blood transfusions, or through mother-to-child transmission during pregnancy. This bacterial infection is caused by Treponema pallidum.

Syphilis can be treated with antibiotics such as penicillin. Furthermore, patients can become reinfected, so early antibiotic treatment is necessary.

After decades of clinical trial missteps, a December 18, 2025, study found syphilis vaccine development is beginning to gain momentum due to advances in understanding the outer membrane protein of Treponema pallidum, host–pathogen interactions, and the genomics of syphilis.

Preventing vertical transmission of Treponema pallidum subsp pallidum could be the most consequential target for a vaccine, given the global resurgence of congenital syphilis and adverse pregnancy outcomes.

As of late 2025, the U.S. Preventive Services Task Force and the American College of Obstetrics and Gynecology recommend that pregnant women be tested for syphilis. And in 2026, Alabama, Arizona, Colorado, Georgia, Maryland, Mississippi, Missouri, North Carolina, Tennessee, and Texas require syphilis testing during pregnancy.