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Japanese officials say that syphilis cases are increasing at the fastest pace on record this year. The National Institute of Infectious Diseases (NIID) reports as of August 24, Japan has recorded 7,525 syphilis cases across the country.

Image/Robert Herriman

This number is already close to 7,983 cases for the whole of 2021, the highest annual total since data under the current format began in 1999.

Tokyo leads the country with 2,178 cases, followed by Osaka prefecture with 1,006 and Aichi prefecture with 425.

According to a Japan Times report, Men accounted for 67% of cases confirmed between January and June 2022.

Women in their 20s and 30s comprised about 75% of all female cases. Many men in their 40s and 50s were also found to be infected.

The Japanese government has mandated that all diagnosed cases of syphilis be reported under the Notifiable Disease Surveillance law since 1948. The annual number of reported syphilis cases throughout the country ranged from 500 to 900 between 2000 and 2012. However, the number has indicated a steady and alarming increase since then: 1228 in 2013, 1661 in 2014, 2690 in 2015, 4575 in 2016, 5826 in 2017, and 7002 (5.6 per 100,000; males, 4588; females, 2414) in 2018 and finally hitting 7,983 cases in 2021.

According to a paper published in the Journal of the Japan Medical Association (JMA) in 2019, changes of sexual behavior or commercial sex work, insufficient funding for prevention, and poor education during school years are possible causes of the increase in the number of sexually transmitted infections (STIs), but the true reasons for the current syphilis resurgence in Japan still remain unknown.


Some hypothesize about its association with the abrupt increase in the number of foreign visitors to Japan, a 3.43 times increase in 2017 compared to 2012. Alternatively, we hypothesized that the explosive spread of specific software applications (apps) on smartphones used to locate and connect with members of the opposite sex (also known as mobile dating apps) launched in 2012, and that had gained wide-ranging popularity since 2013, might have contributed to the significant rise in syphilis cases due to their potential to accelerate casual sex among unfamiliar partners.

At least one academic organization is calling for vigilance as annual syphilis cases are feared to exceed 10,000 this year.

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Syphilis is a sexually-transmitted disease (STD) that can cause long-term complications if not treated correctly. Symptoms of syphilis in adults include a painless sore that will go away without treatment followed by a non-itchy body rash. If left untreated syphilis can lead to damage through the body including neurological and cardiovascular complications. Syphilis also increases the risk of HIV infection and, for women, can cause problems during pregnancy and for the newborn.

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