Streoptoccocal Toxic Shock Syndrome cases in Japan are already higher in 2024 than the year-end total for 2023.
Japanese health officials have noted a record increase in a dangerous and potentially fatal bacterial infection without a clear explanation for the rise.
By early June, Japan’s Health Ministry had counted just under a thousand cases of Streoptoccocal Toxic Shock Syndrome (STSS)—already higher than the year-end total for 2023. This represents Japan’s highest number of STSS cases since the ministry began tabulating statistics over two decades ago. The ministry recorded nearly a hundred STSS deaths in 2023—nearing record levels.
STSS is also present in the United States but at a much lower, stable levels. The U.S. has reported 395 cases so far this year versus 390 at the same time last year—an infection rate some two and a half times lower. The United States has three times the population of Japan.
The United States Centers for Disease Control (CDC) considers STSS a “rare, but serious bacterial infection” that “can develop very quickly into a life-threatening emergency.” People diagnosed with STSS require immediate hospital care. Symptoms include fever and chills, muscle aches, nausea, and vomiting. Advanced symptoms can include low blood pressure and, ultimately, organ failure.
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Japanese health officials are uncertain what caused the increase in cases or how those cases were being spread. The CDC notes that the cause of about half of STSS cases in the United States don’t have an identified transmission source, meaning doctors aren’t able to determine how their patients acquired the bacteria. However, they’ve observed that risk factors are higher for those with open sores or adults over the age of 65.
In late 2022, five European countries reported an increase in invasive Group A streptococcus to the World Health Organization (WHO), with children under 10 years old most affected. Many other countries also noted a rise in cases but also cautioned that the results could have been related to a rollback in COVID-19 controls such as masks and social distancing.
Neither the CDC nor the U.S. State Department have issued travel warnings for Japan. The State Department currently ranks Japan at its lowest risk category, Level 1: Exercise Normal Precautions. Japanese medical facilities are of a high standard, and the State Department does not note any specific health concerns for U.S. travelers intending to travel to the country.
Japan welcomed nearly a quarter of a million U.S. visitors in June 2023.
Although the immediate impact to travel is low, some clinicians in Japan’s medical community are concerned by the increase. Tokyo Women’s Medical University Professor Kikuchi Ken told local news outlet NHK that the surge in patients is alarming because it indicates something new is happening.
Most bacterial infections can be treated with antibiotics, but fast-moving infections can quickly deteriorate systems. With STSS, organ failure can onset quickly. One patient, Tabata Toshinaru, told NHK he developed fever and fatigue, followed by shoulder swelling and pain. By the third day, he noticed a decrease in his kidney function and reported to a local hospital on the third day, where doctors performed life-saving surgery to remove necrotic tissue.
Tabata was relieved at his choice to visit the hospital. “I could have died if I had stayed home to wait and see how things went.” Doctors later told him that the cause of the infection was unclear because he was in his 40s without evidence of a recent wound or surgery.
Kikuchi also says pandemic precautions may be to blame for the spike in bacterial infections.
“We can boost immunity if we are constantly exposed to bacteria. But that mechanism was absent during the coronavirus pandemic,” Kikuchi says. “So, more people are now susceptible to infection, and that may be one reason for the sharp rise in cases.”