The number of syphilis cases in Japan totaled 13,251 this year as of Sunday, hitting a record high for the third consecutive year, national data showed Friday.

The total exceeded the previous annual record of 13,228 cases reported in the entire year of 2022, according to the data released by the Tokyo Metropolitan Infectious Disease Surveillance Center.

While the exact cause is unknown, the number of syphilis cases has surged since 2021 during the COVID-19 pandemic.

Syphilis is an infectious disease caused by the bacterium Treponema pallidum, which is mainly transmitted through sexual contact. After a lump appears on the genitals or other body parts, symptoms such as rashes appear all over the body. If left untreated, it can cause serious complications for the brain and heart.