Despite the prominence in the public mind of China's battle with Severe Acute Respiratory Syndrome, or SARS, many health experts say HIV-AIDS is a greater problem for the country. They also say HIV-AIDS affects far more Chinese than official estimates would suggest.

AIDS in China has been described as a ticking time bomb. Both the Chinese government and the United Nations body, UNAIDS, estimate there are 840,000 to 850,000 Chinese infected with HIV, the virus that causes AIDS. That translates to about 0.1 percent of the country's 1.2 billion people population.

Chinese doctor and longtime AIDS activist Wan Yanhai, the director of the Beijing Aizhixing Institute of Health Education and a visiting fellow at Yale University, says he thinks official estimates are much too low.

"I don't know how the Chinese government gets the figure," he said. "But I do believe the real number is much higher than the Chinese government estimation, and the U.N. estimation."

He points to the scores of people infected with AIDS-tainted blood during the 1990s in a state-run program that used unclean needles in the country's most populous province, Henan.

"There are some figures, that in the 1990's, there were about three million people involved in selling blood," said Wan Yanhai. "So, in Henan, in most of the villages we know, the infection rate among blood donors is about 40 percent to 60 percent. So, just in Henan, the number of people with AIDS just in Henan could be one million or two million."

In China, AIDS is notable for being the disease that has ravaged Africa. But Kevin Robert Frost, with the American Foundation for AIDS Research, or amFAR, says he expects Asia to become the pandemic's next epicenter.

Mr. Frost says his organization has seen some promising signs of increased willingness from the Chinese government to confront its HIV-AIDS epidemic, especially following the SARS crisis earlier this year. But he added that denial of the full extent of the problem still exists.

"Unfortunately, there are no reliable data that accurately assess the scope of the epidemic," he said. "Chinese doctors privately suggest that the epidemic is at least five times, and possibly even 10 times the official estimates."

Mr. Frost says compared to Africa or Southeast Asia, China has a health care infrastructure that functions well. The Chinese government also has shown its willingness to face the problem by offering free AIDS treatment therapy to poor people at public hospitals and clinics in severely affected communities.

But he says just offering the drugs is not enough to effectively combat the disease.

"The mix of insufficiently trained medical staff with poor counseling skills, poorly tolerated drug regimens and lack of testing and laboratory monitoring capacity is a worrisome combination of factors," said Kevin Robert Frost.

Controlling AIDS in China also has a global dimension, a point recently underscored by former President Bill Clinton at an international AIDS meeting in Beijing.

"You can stop this dead in its tracks, you can turn it around and you can manage it now at a small and affordable price," said Bill Clinton. "But if we continue to ignore the implications of AIDS, it will be terrible not simply for China, but for all the friends and partners of China all around the world."

As China continues growing into an economic powerhouse, the country is increasingly in the world spotlight. Chinese AIDS activist Dr. Wan says international attention is important, but incidents like the AIDS blood scandal in the central province of Henan brought the issue home to the Chinese heartland.

"I think international pressure is strong," he said. "It's really important. But I think, without domestic pressure, the Chinese government will not change."

Dr. Wan has been working to help Chinese AIDS patients and publicize the issue for nearly a decade. Because of his efforts, he lost his job at the Ministry of Health in the 1990's and was detained for about a month last year.

This year, though, has been a good year for him and his colleagues working around the country. There has been no trouble from the government and those who were detained have been released from prison. Dr. Wan says he does not know how long this relative leniency will last, but hopes that it is a positive sign the Chinese government is willing to address the problem before it gets out of control.