Tokyo, Sep 3 (IANS): The number of patients across Japan who contracted streptococcol toxic-shock syndrome (STSS) -- a deadly condition commonly known as “flesh-eating disease” -- has reached 291, a record high, the National Institute of Infectious Diseases (NIID) said on Thursday.

The infection, which is fatal in almost one in three cases, destroys tissue and can result in death in a matter of days, the Japan Times reported.

The figures show that cases this year topped last year’s 273 patients in less than nine months.

“Researchers are not sure why the number is growing,” an NNID official said, adding “There is so much we still don’t know about this disease.”

When a person is infected with streptococcal bacteria, he or she will normally develop only minor symptoms such as a sore throat or skin infection.The bacteria commonly exists in the body but does not usually spread to certain organs.

Of the 712 patients reported between 2012 and 2014, 207 or 29 percent of the total, died. As many as 76 percent of the fatalities occurred within three days after symptoms emerged, it said.

The majority of patients are aged over 60 but younger people, including children, also contracted the disease, the NIID official added.