Chinese women's vulnerability to contracting AIDS has almost doubled in the past 11 years, the latest figures show.

By the end of 2009, women accounted for more than 30 percent of the estimated 740,000 cases of HIV in China, compared to 15.3 percent in 1998, according to the latest research by the UNAIDS, announced on Tuesday.

Of these, approximately one-third of newly infected women contracted the disease from their husbands, who were exposed to the virus either through contact with prostitutes or by engaging in homosexual activity, according to the research.

"Women became increasingly vulnerable over the period of research, with sexual transmission accounting for most cases of exposure to the disease," Guo Ruixiang, a China Program Officer for UNAIDS, said on the sidelines of a forum organized by the All-China Women's Federation in Beijing on Tuesday.

Guo said China had 48,000 new cases of HIV infection in 2009, of which 74.7 percent contracted the virus through sexual contact, though it may also be transmitted through blood transfusions, the use of contaminated hypodermic needles and by mother to child transmission (MTCT) during pregnancy or breastfeeding.

The proportion of women among those who contracted HIV through sexual contact rose from 44.1 percent in 2001 to 55 percent in 2004.

"The MTCT ratio increased in line with the number of female infections," Guo said.

The latest reports from the Ministry of Health show that MTCT transmission accounts for 1 percent of total cases of infection in recent years, while China did not have any MTCT cases 15 years ago.

"We should root out societal expectations regarding sex if we want to reduce women's vulnerability," said Min Ziping, head of the women development department of the Hubei Provincial Women's Federation.

"Women traditionally have less say over condom use, which has made them more vulnerable to infection," she said.

The federation conducted research on female HIV infection, in which 90 percent of respondents said women were unable to assert their right to protect themselves.