Returning threat

Syphilis was almost eradicated in China in the 1960s and 1970s thanks strict nationwide efforts to control the spread of the disease.

One contributing measure unleashed in the 1950s was a tough crackdown on the commercial sex industry. Police closed hundreds of brothels, while thousands of prostitutes were treated with penicillin and offered health advice on how to prevent contracting STDs.

"Although syphilis was virtually wiped out at that time, the source of infection lingered in some regions, particularly in ethnic minority areas," said professor Wan.

By the 1980s, as the country opened up and moved increasingly towards a market-orientated economy, a threat also came from the droves of foreigners who were arriving not only with new ideas and technology, but also the syphilis virus. This fact, coupled with an increased demand for sex workers from rich business leaders and migrant workers, has helped steer a sharp upward curve in reported cases over the last two decades.

The number of infections jumped from 1,982 in 1991 to 306,381 in 2009, according to Ministry of Health statistics, putting syphilis third in the nation's list of the most dangerous infections diseases.

Research published in the Lancet indicated there are now about six cases for every 100,000 people in China.

"The bacterial infection reemerged in the 1980s as the economic boom increased migration to cities by rural workers," explained Chen Xiangsheng, deputy director of China's National Center for STD Control, in a recent World Health Organization bulletin. "Migrant workers, mainly young men who have left their wives back in their hometowns, make up much of the clientele of low-tier sex workers.

"It's difficult to promote condom use among these prostitutes because they are poorly educated and some cannot even afford a condom," added Chen, who co-authored the paper on syphilis published in the New England Journal of Medicine.

Infection rates have also soared among farmers and retired people, according to a 2006 report on syphilis and gonorrhea by the STD center of the Chinese Center for Disease Control and Prevention.

"Even if they know they have caught syphilis or another STD, these three groups are often too ashamed to see a doctor because of the stigma, and will most likely pass the virus to their spouses," said professor Gong Xiangdong at the STD center.

Chinese people are still deeply conservative when it comes to discussing sexual health, and discrimination against those diagnosed with STDs, as well as many other conditions, remains a real problem.

Because of this reason, studies that suggest more than half of China's syphilis sufferers do not seek the medical treatment they need.