Japan has reported a record surge in streptococcal toxic shock syndrome (STSS) cases, with 977 infections and 77 deaths recorded between January and March 2024, the Health Ministry announced on June 2, 2024.

This unprecedented spike in STSS cases, which has already surpassed last year's record numbers, underscores the severe impact of this rare but deadly bacterial infection. Experts are investigating potential causes, with some attributing the rise to weakened immune systems following the COVID-19 pandemic. The alarming increase has prompted calls for heightened surveillance and preventive measures, particularly for those at high risk.

Streptococcal toxic shock syndrome (STSS) is caused by group A streptococcus (GAS) bacteria, which are known for their ability to cause various severe illnesses such as strep throat, scarlet fever, and skin infections. STSS, however, is one of the more dangerous manifestations, characterized by rapid onset and severe symptoms including fever, chills, muscle pain, swelling, and vomiting. The condition can quickly progress to life-threatening complications like low blood pressure, organ failure, and rapid breathing.

STSS poses a significant mortality risk, with an estimated fatality rate of up to 30%. The infection can further complicate into necrotizing fasciitis, often referred to as 'flesh-eating disease,' which can lead to limb loss. Between January and March 2024 alone, 77 deaths were attributed to STSS in Japan, showcasing the disease's lethal potential.

The recent surge in STSS cases is not an isolated event. Japan saw a record-breaking 941 STSS infections in 2023, and the continuing upward trend in 2024 has surpassed this prior record. Japan's National Institute of Infectious Diseases released a risk assessment in March 2024 highlighting an increase in STSS cases since July 2023, particularly among individuals under the age of 50. This report emphasizes the urgent need for preventive and control measures to address the growing threat.

One contributing factor to the rise in invasive group A strep infections, including STSS, could be the relaxation of public health measures previously implemented to curb COVID-19. With the easing of mask-wearing, social distancing, and hand hygiene practices, infectious diseases that were previously suppressed have resurfaced. This phenomenon has been observed not only in Japan but also in several European countries and the United States since late 2022.

Internationally, similar increases have been reported. Five European countries, including the United Kingdom, Ireland, France, the Netherlands, and Sweden, recorded spikes in invasive group A streptococcus (iGAS) infections toward the end of 2022. The Centers for Disease Control and Prevention (CDC) in the United States is also investigating an uptick in iGAS cases, reporting 395 STSS cases so far in 2024.

Professor Ken Kikuchi has provided insights into possible causes for the rise in STSS cases, suggesting that the widespread decrease in immune function following the COVID-19 pandemic may have contributed. The pandemic has had far-reaching impacts on public health, and weakened immune defenses could create a fertile environment for opportunistic bacterial infections like STSS to flourish.

To mitigate the risk of STSS, various preventive strategies have been recommended. Vaccination against chickenpox and influenza, which can predispose individuals to secondary bacterial infections, is crucial. Additionally, providing antibiotics to individuals at high risk or those in close contact with STSS patients can help prevent the spread of the bacteria.

Certain demographics are particularly susceptible to STSS. The condition is most frequently observed in adults over the age of 65, but other risk factors include infections or injuries that break the skin barrier, and pre-existing health conditions like diabetes and alcohol use disorder. These factors necessitate targeted preventive measures to protect vulnerable populations.

The ongoing rise in STSS cases underscores the need for vigilant infectious disease surveillance and control both in Japan and globally. Health authorities and researchers must work together to identify underlying causes and develop effective strategies to curb the spread of severe bacterial infections. Enhanced public health initiatives, awareness campaigns, and adherence to preventive measures can play a key role in reducing the incidence and impact of STSS.

As the investigation into the rising STSS cases in Japan continues, the healthcare community remains on alert. The situation highlights the critical importance of preparedness and adaptability in public health efforts. Robust surveillance systems, prompt medical interventions, and community engagement will be essential in managing and eventually overcoming the ongoing threat posed by STSS.