Syphilis Cases Hit Record High for 3rd Straight Year in Japan

The Yomiuri Shimbun file photo
National Institute of Infectious Diseases

Tokyo (Jiji Press)—An epidemic of syphilis is a serious concern in Japan, with the number of reported cases in 2023 hitting a record high for the third consecutive year on a preliminary basis.

Additionally, the number of congenital syphilis cases, which result from bacterium transmission from infected pregnant women to their fetuses through placentas, has reached an all-time high.

Syphilis is an infectious disease caused by a bacterium called Treponema pallidum. Primarily transmitted through sexual contact, infection can result in the formation of lumps or sores in the genitals or the mouth, accompanied by swollen lymph nodes and a rash that spreads across the body. Diagnosis of the infection typically involves blood tests.

Even if symptoms appear mild, untreated syphilis can cause severe complications, particularly affecting the brain or heart. Also, the disease can be transmitted by infected individuals who show no symptoms themselves.

While the use of condoms is effective for prevention, it does not guarantee complete protection, and individuals can be reinfected even after recovery. Early treatment with penicillin antibiotics is effective and can completely cure the disease.

“Syphilis can be cured quickly if detected promptly,” an expert said. “If you have any concerns, it’s important to undergo testing.”

According to the National Institute of Infectious Diseases, the reported number of syphilis cases in 2022 totaled 13,228,

surpassing 10,000 for the first time since 1999, when the current survey method was first used. In 2023, reported cases surged to 14,906.

A breakdown by prefecture shows that Tokyo reported the highest number, at 3,658, followed by Osaka at 1,967, Fukuoka at 939, Aichi at 817 and Hokkaido at 677. These statistics underscore the ongoing trend of cases occurring predominantly in urban areas.

Congenital syphilis can cause premature births and stillbirths, as well as intellectual, visual and hearing disabilities. The reported number of cases had remained around 20 per year since 2018 before jumping to 37 in 2023 on a preliminary basis. Some experts speculate that the surge may be linked to the overall increase in the number of patients.

Historically, the annual number of syphilis patients exceeded 10,000 in the second half of the 1960s but declined later, standing at between 500 to 900 cases in the 2000s. Since the 2010s, however, the number has been on the rebound, with a spike observed during the COVID-19 pandemic from 2020 onward.

By age, prevalence is notably high among men in their 20s to 50s and women in their 20s.

While the precise reasons for the surge in reported cases remain unclear, experts have identified several potential contributing factors. These include increased promiscuity linked to encounters with many people through social media, as well as the utilization of sex-related businesses. In addition, there may be missed diagnoses by doctors with limited experience in treating the disease. These concerns were highlighted by Hiroshige Mikamo, a professor at Aichi Medical University who leads anti-syphilis measures at the Japanese Society for Sexually Transmitted Infections.

One survey suggests that the actual number of patients may be five times higher than the reported number, underscoring the seriousness of the situation.

Mikamo strongly encourages people to undergo testing if they or their partners have engaged in sexual activities that pose infection risks, or if they have acquired new partners. “To prevent the further spread of infections, we urge people not to hesitate in getting tested if they have even the slightest concern,” he said.