Syphilis is spreading in Japan faster than it has in more than two decades. Experts say cases of the disease are likely to exceed 10,000 in one year.

Syphilis is a bacterial infection that is mainly transmitted through sexual contact. Those who get the disease may show no symptoms or symptoms that disappear soon. It is curable, but if not treated, it can cause serious problems in the brain or heart.

Japan's National Institute of Infectious Diseases says 7,013 cases were reported nationwide from January through August 7. That's 1.7 times the figure reported for the same period last year.

If cases continue to grow at the current pace, the total for this year could exceed 10,000 for the first time since 1999, when comparable data first became available.

Of the cases reported by July 3, 67 percent of the carriers were men.

Regarding the female carriers, those in their 20s and 30s accounted for 75 percent of the total. Infections in men were more widely distributed, with those in their 20s accounting for 22.4 percent, their 30s 25.4 percent, their 40s 25.8 percent and their 50s 16.4 percent.

Syphilis treatment experts say it is important to use condoms to prevent infection, but that condoms are not 100 percent effective. They urge those who have had risky sex to get tested for the disease even if they have no symptoms.