Anton Qiu plans to roll up his sleeve this morning and have a blood test technician slip a needle into his arm. Within two weeks he will learn whether he is a carrier of hepatitis B, the leading cause of liver cancer in the world.

A quarter century after the first hepatitis B vaccine became commercially available, rates of acute infection with the liver-scarring virus have plummeted in the United States, but the disease remains endemic in Asia - and 1 in 10 of the estimated 10.3 million Asian adults living in the United States are believed to be chronically infected.

About 1 in 4 of those chronically infected people - known as hepatitis B carriers - will eventually die from scarring of their liver tissues, or from liver cancer. San Francisco, where one-third of the population is of Asian descent, has the nation's highest rate of liver cancer.

"I've had cousins and distant relatives who died of this," said Qiu, 48, a real estate investor who came to the United States as a student from Shanghai in 1980.

Today, he'll join at least 1,000 others attending the Asian Heritage Festival in Japantown who are heeding a call from civic leaders in their communities to get tested.

Among those leaders is Assemblywoman Fiona Ma, D-San Francisco, who learned when she was 22 years old that she is a hepatitis B carrier.

The silent epidemic

"In the Asian community, it is taboo to talk about any flaws, to talk about anything health-related," Ma said in a recent interview. "But this is a silent epidemic. You don't have symptoms until it is too late. The more we talk about it, the more we can share stories, and encourage their families and friends to talk about it."

Two-thirds of the estimated 1.25 million hepatitis B carriers in the United States do not know they are infected and are unlikely to find out until they show signs of potentially life-threatening illnesses. Ma was infected at birth, but didn't know she was a carrier until she took a blood test during a job application process.

She was born in the United States, but her parents are from China. Her mother is a hepatitis B carrier, as is her brother. But their youngest sister, born after the vaccine became available, is immune. All in Ma's family remain healthy, and with regular blood testing to find any signs of liver damage, they expect to remain so.

The hepatitis B virus is about 100 times more infectious than HIV, the virus that causes AIDS. Like HIV, it can be transmitted sexually, during childbirth or by the sharing of needles. Unlike HIV, it is preventable with a vaccine. It is also treatable.

The hepatitis B vaccine, initially derived from human blood but now produced in yeast through genetic engineering, has the potential to eliminate the disease among the youngest Americans. Since 1991, the federal Centers for Disease Control and Prevention has recommended that all newborns be vaccinated against the virus, and state law requires it - although parents can seek a waiver to opt out of the requirement.

The vaccine has helped to lower the number of acute hepatitis B infections - a condition marked by fatigue, nausea, abdominal pain and yellowing of the skin and the whites of the eye. In San Francisco, where hepatitis B was circulating among gay men as well as in the Asian community, the rate of new infections has fallen nearly 90 percent since it peaked in 1987.

In addition, treatments using immunoglobulin and vaccine have reduced the risk of mothers transmitting the virus to their babies in childbirth by up to 95 percent, said Dr. Sandra Huang, director of communicable diseases for the San Francisco Department of Public Health.

Tracking and treating chronic hepatitis B infections is a more difficult challenge, because the disease does not reveal itself in most chronic carriers unless and until they become ill. Newborns and children are most susceptible, yet show few if any symptoms of infection. Huang said that, for now, San Francisco health officials can make only a rough estimate that there are 20,000 residents living with chronic hepatitis B infection in the city.

Bay Area concentration

The Bay Area has a high number of hepatitis B chronic infections because the region is a gateway for immigration from China, where an estimated 120 million are carriers. "China alone accounts for 50 percent of liver cancer deaths in the world," said Dr. Samuel So, a surgeon and director of the Asia Liver Center at the Stanford University School of Medicine. "Every day, over 1,000 people in China die of this disease."

So has been working with the federal Office of Minority Health on development of a nationwide strategy to control hepatitis B. Currently, the agency is spending $500,000 of its $50 million annual budget on hepatitis programs for Asians and Pacific Islanders.

"A lot of folks just don't know how important this epidemic is," said Dr. Garth Graham, director of the agency. "Half of the 1.5 million affected in the United States are Asian Americans."

So is also trying to drum up interest at the World Health Organization and other international bodies to develop a comprehensive strategy to roll back this vaccine-preventable disease. Hepatitis B is also a major health problem in Africa, Southeast Asia and India. Worldwide, an estimated 370 million are infected with the virus, and each year 700,000 die of its complications.

If signs of liver disease begin to emerge, there are drugs that can reduce the amount of virus circulating in the bloodstream and tests that can spot liver cancer before tumors become almost invariably lethal.

"A lot of people who are walking around with hepatitis B have a very treatable disease," said Dr. Alex Monto, director of the liver clinic at the VA Medical Center in San Francisco. "There are medications that are quite new and very effective, and a lot of people do not know about them."