More than 85 percent of new cases of HIV and AIDS in Guangdong province resulted from unprotected sex, a senior health official has revealed.

The figure has risen sharply from 57.4 percent just two years ago, and is well up on the 37.6 percent of 2008, according to the Guangdong Center for Disease Control and Prevention.

"The steady growth in HIV and AIDS is a serious threat," said Lin Peng, head of its HIV/AIDS prevention center.