In a nation where AIDS has been shrouded in silence, China's Dr. Wan Yanhai speaks loud and clear -- sometimes at his own peril.

Wan has been an outspoken critic of the way the Chinese government has handled the AIDS epidemic in the world's most populous country, and a tireless advocate for public health and AIDS patients in China. For his work, he has been harassed, accused of leaking state secrets and arrested. An international outcry helped get him out of jail.

Wan's AIDS work and his public fight have come at a crucial point for curbing the epidemic's spread in Asia. Reports of a growing problem in China's countryside -- where most of the country's people live -- have been denied by officials for years, until the central government surprised the world by formally acknowledging the scope of the HIV/AIDS epidemic in China this fall and asking for international help.

The timing of that political shift could not be more critical. International health experts say the two largest countries in Asia -- China and India -- face an AIDS crisis similar to that of sub-Saharan Africa unless massive public health campaigns can bring the epidemic under control.

If they do not, the already heavy local and global costs -- in lives, in international aid and in the worldwide spread of HIV/AIDS -- will be enormous. In a visit to China last month, United Nations Secretary-General Kofi Annan warned that ``China stands on the brink of an explosive AIDS epidemic.''

Wan, the coordinator for an influential health effort in China known as the the Aizhi (Beijing) Action Program, is a former Chinese government health official. At 39, he speaks with the frustrated voice of a doctor who has seen too many people fall ill.

He says the government-controlled newspaper China Health News has covered up the growing AIDS epidemic. He is particularly angered by the large-scale, uncontrolled and illegal sale of blood plasma in many villages in eastern and southern Henan province, which has fueled the spread of AIDS in this poverty-stricken area.

The government has tried to suppress news of the growing epidemic, he said. In November, officials in Suixian County detained poor farmers with AIDS, as well as Chinese journalists who had come to interview them. In Chengguan Township, 11 HIV-infected peasants and three journalists were held at a government facility.

``Issues are still covered up by local and central governments,'' Wan said in an interview in San Francisco last week. ``There are no social resources. People are not allowed to be prepared.''