Retired physician Gao Yaojie, in her 80s, is among China's most prominent and tenacious AIDS activists. She received numerous awards for efforts a decade ago to alert people in her home province of Henan, in eastern China, to an AIDS outbreak being spread by tainted blood transfusions.

Henan authorities warned Gao not to attend the Vital Voices Global Partnership awards ceremony next month but she refused to comply, said Hu Jia, a Beijing-based AIDS activist and friend of Gao's.

Zhengzhou city authorities detained her at home Thursday ahead of a planned trip to Beijing on Sunday to apply for a U.S. visa, Hu said.

He said friends and family who tried to visit Gao at home were being blocked or interrogated before being allowed in, and her daughter was under constant police surveillance.

In the late 1990s when the government was tightlipped about its AIDS problem, Gao spoke openly to the press and distributed brochures about the spread of the disease among poor farmers because of the blood-buying industry. Health officials then accused her of helping "anti-China forces."

Chinese leaders have shifted gears dramatically in recent years, confronting the disease more openly and promising anonymous testing, free treatment for the poor, and a ban on blood sales and discrimination against people with the virus.

But AIDS workers still face frequent harassment by local authorities who fear their activism will reflect badly on them, possibly jeopardizing their jobs or chances for advancement.

Gao was refused a passport in 2001 to go to Washington to accept an award from a U.N. group.

A man who answered the phone at the Zhengzhou Public Security Bureau refused to answer questions about Gao. Like many Chinese officials, he refused to give his name and referred calls to the provincial government.

A Henan government official, who would identify himself only by the surname Wu, said he was unclear about the case.

Gao's and her daughter's phone numbers both rang unanswered yesterday.

Hu said Gao was to be honored for her work promoting women's legal rights in China at a March 14 Vital Voices Global Partnership annual awards dinner in Washington. Clinton is one of the group's honorary chairwomen.

Vital Voices provides global aid and training to women to help them be more active community leaders. The group's board members include businesswoman Carly Fiorina and actress Sally Field.

Gao's activism began in 1996 when she wrote and printed copies of a basic AIDS information pamphlet for distribution at Zhengzhou's long-distance bus stations.

Since then, she has distributed medicine, cared for AIDS orphans, written a book about China's AIDS epidemic and hosted AIDS sufferers in her modest apartment. Funding comes from her own earnings and occasional donations.