Through December 17, 2025, officials with the Japan National Institute of Infectious Diseases (NIID) report 13,085 syphilis cases after reporting 185 during week 50.
Tokyo reports the most cases with 3264, accounting for 25 percent of all cases nationwide. This is followed by Osaka with 1637 cases, Aichi with 818 cases, Fukuoka with 739 cases and Kanagawa prefecture with 728 cases.
This is the fourth year in a row Japan has recorded at least 13,000 syphilis cases.
In 2024, 14,663 cases were reported, just shy of 2023 case total of 14,906 total cases. In 2022 (the first time eclipsing the 10,000 mark), Japan saw 13,228 cases.
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, 7002 in 2018 and 7,983 cases in 2021.
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In Tokyo, officials say that the increase is likely due to the ease of meeting and hooking up with strangers. Some experts say another cause of the increase is people’s unwillingness to discuss STDs, combined with a general lack of knowledge or belief in erroneous information.
The increase is most marked in men between the ages of 20 and 50 and women in their 20s.
With the rise in syphilis in Japan, congenital syphilis has also increased, hitting a record at 37 in 2023.
In a 2022 survey by the Japan Association of Obstetricians and Gynecologists, one in about 200 pregnant teens was infected with syphilis in 2022, a nearly threefold increase in about six years.
The survey received responses from 1,346 medical institutions nationwide that deliver children.
It found that 18 of 3,504 pregnant teens, or 0.51 percent, were infected, compared with 0.19 percent in the previous survey, which covered six months from October 2015.
Syphilis is a bacterial infection caused by Treponema pallidum, which results in substantial morbidity and mortality. It is a sexually transmitted infection (STI) that is generally transmitted by contact with infectious sores on the genitals, anus, rectum, lips, or mouth; through blood transfusions, or through mother-to-child transmission during pregnancy.
Syphilis can be treated with antibiotics such as penicillin, but if left untreated, it can cause damage to the heart, blood vessels and nervous system after several years or even decades. A patient could become infected again, so early treatment with antibiotics is necessary.
AloJapan.com