By Jill McGivering
A new report published in a leading medical journal suggests China is seeing alarming and rising rates of the sexually transmitted disease, syphilis.
Syphilis is most prevalent amongst those in high-risk groups
The Lancet reports that China - which virtually eliminated syphilis in the 1960s and 70s - is now seeing the disease return with alarming intensity.
It reveals that reported rates have risen from 0.2 cases per 100,000 in 1993 to 5.7 cases per 100,000 in 2005.
Dramatic intervention is now needed, one of the report's authors says.
The study involved doctors from China's National Centre for STD Control in Nanjing and from the University of North Carolina's School of Medicine.
Dr Myron Cohen, a co-author of the report, described the spread of the disease as "fantastically rapid".
The disease is most prevalent amongst those in particular high-risk groups, like commercial sex workers and men who have sex with men. In those groups, as many as one in ten to one in five has syphilis, according to some of China's top specialists.
But syphilis is also spreading quickly in the general population. An area of particular concern is the surge in congenital syphilis - the number of babies born with the disease, after contracting it in utero from infected mothers.
It is reported that about 3,400 Chinese babies are being born each year with congenital syphilis. The figure has risen dramatically since 1991 - by more than 70% each year.
Syphilis is an aggressive and dangerous disease in itself - but Dr Cohen says its rise also has wider implications, giving a sense of the rapid spread of other sexually transmitted diseases (STDs) too.
"If we are seeing syphilis spread, we have to be concerned that other STDs are spreading as well," he told the BBC.
"Also we have reason to believe that syphilis helps to drive HIV. So we have to be concerned that untreated syphilis will amplify the spread of HIV as well."
So why is there such dramatic spread? It is being fuelled in part by rapid social change.
The large numbers of migrant workers in China, increasing prostitution and more extramarital sex - along with low condom use - are all key factors.
The need to pay for health care now may deter people from getting early tests and treatment.
Chinese society is still deeply conservative with little open discussion about sex at any level.
That severely inhibits the exchange of information at all levels, from within families and sexual relationships to information campaigns in schools, universities and in the media.
There may even be a biological reason too for the rapid rise.
Chinese adults, who are sexually active now, had no exposure to syphilis for decades. Some scientists say that has left today's population with very little immunity to it.