Thailand has seen a 300% increase in the number of new syphilis infections in the past decade. Three thousand cases were diagnosed from January to May this year. Syphilis is a sexually transmitted disease that can also be transmitted via blood. Although it's a sexually transmitted disease that is easy to cure, it is a serious public health concern, not only in Thailand but worldwide due to its global reach. CGTN's Dusita Saokaew has more.

It is a topic rarely discussed freely in Thailand. And inside this high school classroom in Bangkok, sex education class is received with moments of embarrassment, mockery and nervous giggles. But outside these classroom walls, it's a different story. The average age of Thais having the first sexual encounter is getting younger and now at 13-15 years old- 50% without a condom according to the Health Ministry.

DUSITA SAOKAEW BANGKOK "The problem is lessons learned these sex-ed class, for many, does not translate into action. Many teens are complacent about sexually transmitted infections. A serious concern considering Syphilis in Thailand has now reached alarming rates and about 37% of new infections recorded last year were found among those aged between 15 to 24."

We asked this group of 18-year-old students what they know about Syphilis? Their response. You could be forgiven for not knowing much about syphilis. It was after all considered a practically ancient ailment. But its incidence has been rising almost every year for the past 10 years in Thailand from 2-3 cases to now 12 per 100,000 population. That's almost a 300% increase. But this spike is being experienced around the globe. Cases in Japan have hit a 50-year high. Western Europe saw increases of over 50% in new cases. Even in the US, a 73% increase in the rate of infection from 2013-2017.

DR. ROSSAPHORN KITTIYAOWAMARN BANGRAK STIS CLINIC "In Thailand, people mostly used to go and pay for sexual services. Now, society has changed and encounters can happen everywhere and it's becoming more casual."

The disease is curable with antibiotics, but it's a bit of a secret agent, transmissible through almost every sexual means and erupting as a tiny lesion about a month after exposure. At various stages of the infection, it might cause no symptoms or a puzzling array of them. If gone undiagnosed, it can cause everything from disfigurement to seizures. Mond happens to be one of the unlucky ones. He came to Bangrak STI Clinic in Bangkok as rashes started to appear. His tests came back positive for syphilis, a disease he knew nothing about.

MOND SYPHILIS PATIENT "I've never heard about this disease. I came here because I thought I had something else. I only just found out about this on the posters on the wall."

And there lies the problem. Today, syphilis has somewhat been forgotten. And that is what makes it so dangerous. Because after all, it hasn't disappeared. London today, Tokyo or Bangkok tomorrow and a different bedmate at each stopover, and with that, the chance of getting infected with syphilis increases as containment becomes virtually impossible.