It sounds like the stuff of horror movies, but Japan is seeing record levels of a highly fatal "flesh-eating" bacterial infection.

Official figures show there have been over 1,000 cases of streptococcal toxic shock syndrome (STSS) since January in the country, surpassing the total number recorded last year.

STSS is a rare but serious disease typically caused by infection with the bacteria Streptococcus pyogenes. It initially causes fever and throat infections but can develop very quickly into a life-threatening emergency, causing "toxic shock” and organ failure within days of infection.

"Even with treatment, STSS can be deadly. Out of 10 people with STSS, as many as three people will die from the infection," say the US Centers for Disease Control and Prevention (CDC) on their website.

Why are STSS cases rising in Japan?

The reason for the sudden rise in STSS cases in Japan remains unclear to health professionals.

"Experts don't know how the bacteria got into the body for nearly half of people who get STSS," according to the CDC.

In March, Japan's National Institute of Infectious Diseases (NIID) also said, "There are still many unknown factors regarding the mechanisms behind fulminant (severe and sudden) forms of streptococcus, and we are not at the stage where we can explain them."

STSS occurs around the world at low levels, but the recent rise in cases in Japan has caused concern among health experts concerned that bacterial infections could spread to other countries. 

Currently, there is no indication that STSS is spreading beyond normal levels elsewhere in the world. In the US, for example, the CDC has counted 395 reported cases so far this year, which is similar to the 390 reported at this time last year.

Why is STSS so deadly?

Many people carry Streptococcus pyogenes on their skin without ever getting sick, but the bacteria can cause serious STSS if they get into the bloodstream or deep tissue. STSS develops when the bacteria spread into deep tissues and the bloodstream and begin to produce exotoxins. Exotoxins are toxic compounds that destroy cells and tissues in our bodies — hence the term "flesh eating bacteria."

If the bacterial infection gets out of control, it can lead to organ failure and turn fatal. STSS is particularly deadly because of the rapidity of organ failure after infection. After the onset of initial symptoms like fever, aches, and nausea , it only takes about 24 to 48 hours for low blood pressure to develop.

Once this happens, STSS quickly turns much more serious. Heart rate and blood pressure change, and organs like the kidneys or liver begin to fail.

STSS is normally treated in a hospital with antibiotics like ampicillin. However, some strains of Streptococcus pyogenes have shown antimicrobial resistance (AMR) to a range of antibiotic agents. 

To prevent the bacteria from spreading further around the body, infected tissues can also be surgically removed.  

Is STSS infectious?

However, the CDC warns that less severe bacterial infections, like a Group A strep infection, can also turn into STSS. Group A strep bacteria are much more contagious, spreading via talking, coughing, or sneezing or via direct contact with infected skin sores.  

STSS is most common in older adults over 65 years old, as well as in people with health factors like diabetes or alcohol use disorders.  

Open wounds also increase the risk of developing STSS. Therefore, it is recommended that people with recent surgeries or those who have viral infections that cause open sores (e.g., chickenpox or shingles) cover wounds to reduce the risk of being infected with Streptococcus pyogenes. 

The CDC also recommends people avoid contact with others who have Group A strep infections, and receive treatment for them as soon as possible.  

Edited by: Derrick Williams