Awareness campaigns should target the sex industry, the study says

Researchers from the United States and China say they have discovered that a significant number of Chinese adults are infected with chlamydia.

This is due to changing sexual practices, and the researchers warn that the spread of chlamydia - a generally symptomless disease - could also blaze a path for higher HIV and Aids infection rates.

"China is only now beginning to suffer the ravages of HIV, and the unexpected prevalence of chlamydia and attendant high-risk behaviour are critical and instructive warning signs," said researcher Dr Myron Cohen of the University of North Carolina.

In parts of China, men in particular are swiftly becoming more prosperous - and as they get richer, they are paying for sex more and more.

"A lot of businessmen and higher officials use going to sex workers as a part of their doing business," said William Parish from the University of Chicago, also one of the study's authors.

"And therefore these high-income men are bringing the infection home to their wives. The long-term problem of course is that these high-income men are soon going to be picking up HIV, which can't be cured."

Infertility risk

The study, published in the Journal of the American Medical Association, shows that chlamydia rates are as follows:

• overall 2.1% of men and 2.6% of women - similar to developed countries

• 14.6% of men who have sex with prostitutes, and 6% of those men's partners

• incidence highest in the rapidly developing southern coastal region, affecting 16% of men and 9.9% of women

Genital chlamydia, which is usually treatable with antibiotics, is a fairly common sexually transmitted disease (STD), but if left untreated it can lead to female infertility.

China does face a crisis and an opportunity to avert a public health tragedy Chris Beyer John Hopkins Bloomberg School of Public Health China's sex bomb

"The silent chlamydia epidemic may cause many women to be infertile, to have ectopic pregnancies [outside the uterus], and be at greater risk of HIV infection," Mr Parish said.

The researchers are urging the Chinese authorities to implement safer sex programmes, especially aimed at the sex industry.

In an editorial accompanying the study, Chris Beyer of John Hopkins Bloomberg School of Public Health in Baltimore, said action was needed.

"The African experience shows that once HIV is widely transmitted among reproductive-age adults, prevention becomes much more difficult.

"China does face a crisis and an opportunity to avert a public health tragedy," he said.

According to UN figures, 10 million people in China could be infected with HIV by the end of the decade.