Syphilis patients surging in Japan in 2022

TOKYO -- Cases of syphilis are surging across Japan, with the number of patients so far this year up 1.6 times compared to the same period in 2021 -- a year that saw record-high case figures -- prompting medical specialists to warn that it has become a "common" sexually transmitted disease.

Syphilis patients have been on the rise across the country since 2011, with explosive growth seen from 2013. According to the National Institute of Infectious Diseases (NIID), preliminary case numbers in 2021 reached 7,875, surpassing the previous high of 7,007 recorded in 2018. As of April 10, 2022, 2,592 patients had been reported nationwide according to preliminary figures -- a significant rise from the 1,595 cases recorded during the same period last year.

Infections have spread for more than a decade in Japan, with rising case numbers attributed to an increase in the number of inbound tourists and people hooking up with partners they have met through social media, but the exact cause remains unknown.

The infection rate when a person has sex with a syphilis patient is high, at around 30%. However, it is thought that patients tend to be unaware they are infected and fail to take tests or undergo treatment, which in turn accelerates the spread of infections.

Syphilis is transmitted through sexual intercourse or other bodily contact when the bacterium "Treponema pallidum" penetrates the body through invisible minor cuts in the skin or mucous membrane of the genitals or the mouth. Two to three weeks after transmission, a lump as hard as ear cartilage emerges in the genitals or other parts of the body. After two to three months, a rash appears across the entire body, including the palms and the soles of the feet, mostly without pain or itchiness.

Patients can recover if they take oral medication in the early stages of the disease, but if it is left untreated, patients may die from serious complications after the bacterium affects the brain, eyes, heart and nerves over the course of a period ranging from several to more than 10 years. There is no permanent immunity to syphilis, and the same patient can be infected twice or more.

"Syphilis has become a common venereal disease," said Yukari Kugishima, a doctor and the head of Shinjyuku Ladys Clinic in Tokyo's Shinjuku Ward. The number of patients diagnosed with syphilis at the clinic has shown a pronounced increase since August 2021, with the figure climbing to 19 in January this year and 12 in February -- the highest levels in five years.

Many of the patients who visit the clinic work in the sex industry. While some sex shops require workers to regularly submit their test results, there are establishments that do not take any measures against sexually transmitted infections.

"Not a few people hesitate to undergo testing because of the cost," Kugishima said. "In an industry where workers are at risk of contracting STDs, it is necessary to devise a system that can reduce the cost burden on people taking the tests."

Under Japan's infectious diseases prevention law, doctors who diagnose patients with syphilis are required to report each case to a public health center. Between October and December 2021, the number of syphilis patients reported in Tokyo stood at 675, followed by 247 in Osaka Prefecture and 135 in Aichi Prefecture. In contrast, while Tokyo topped the list of prefectures in terms of reported syphilis cases per million people, at 49.9, Kochi Prefecture ranked second at 30.2, followed by Osaka, Okayama, Fukushima, Hiroshima and Kagawa prefectures at 20-plus each, indicating that the growth in the number of cases is not just limited to urban areas but is also observed in regional areas.

By gender and age, women in their 20s formed the largest group of syphilis patients reported in 2021. Amid the rising infections among women, it is feared that the fetuses of pregnant women could contract congenital syphilis through the placenta, which can lead to stillbirths. Over the past several years, the number of congenital syphilis cases has hovered around 20 per year, with 21 newborns under the age of 1 confirmed to have the disease in 2021.

Says Kugishima, "Just as the transmission risk for respiratory infections such as the coronavirus can be reduced by wearing masks, the risk of contracting STDs can be lowered through the use of condoms." She added, "That said, wearing condoms cannot completely prevent transmission. People who perform sexual acts with multiple individuals should often take tests, and those who have one single partner are advised to take the tests when they change their partner, along with the other party."

(Japanese original by Sooryeon Kim, Lifestyle and Medical News Department)