Sexual transmission has overtaken drug use as the main cause of the spread of the HIV/AIDS virus in southwest China's Yunnan Province where AIDS has killed up to 11,609 people in the past two decades, local health officials said Monday.

Yunnan neighbors Asia's notorious opium producing region, known as the "Golden Triangle" stretching across the mountainous borders of Myanmar, Thailand and Laos. The sharing of contaminated needles among drug users was the most common cause of transmission in Yunnan in the past.

But about 71 percent of new infections reported to the health authorities in the first 10 months this year were a result of sexual contact, said Xu Heping, vice director of the provincial health bureau.

About 8,670 people living with HIV/AIDS were reported in Yunnan from January to October. More than 2,000 patients died of AIDS in that period.

The number of infections through sex was up 6.7 percent from the same period last year, Xu said. A fifth of new cases contracted the virus from a spouse.

"The epidemic spread among spouses is alarming," Xu said.

The ratio of infections through drug use had been declining steadily since 2005, while infections among prostitutes remained largely unchanged, Xu said.

Health experts say the spread of HIV/AIDS through spouses indicates the virus is spreading from high risk groups to the general public.

About 740,000 people live with HIV/AIDS in China, according to government statistics.