Shuping Wang, a medical researcher who defied Chinese authorities in the early 1990s by exposing the burgeoning HIV epidemic in one of her country’s poorest provinces, where an estimated 1 million destitute farmers sold their blood plasma at collection sites and were infected with the deadly disease, died Sept. 21. She was 59.

She was hiking in a canyon in Salt Lake City when she suffered an apparent heart attack, said her husband, Gary Christensen.

Dr. Wang had lived for the past 18 years in the United States, becoming a naturalized U.S. citizen, but continued to contend with the intimidation by Chinese government officials that had helped drive her from her home.

As recently as last month, she had said, Chinese police called on her friends and colleagues in Zhoukou, the city in Henan province that was the site of much of her whistleblowing work, in an effort to pressure Dr. Wang to halt a play about her story on stage at the Hampstead Theatre in London.

“The only thing harder than standing up to the Communists and their security police is not giving in to pressure from friends and relatives who are threatened with their livelihoods all because you are speaking out,” she said in a statement on Sept. 3. “But even after all this time, I will still not be silenced.”

Among AIDS activists and others who followed her work, Dr. Wang was regarded as a heroine who risked her career and safety to expose the rampant spread of hepatitis C and HIV among poor villagers recruited by the government to sell their blood plasma for medical purposes.

“Extend your arm. Expose a vein. Make a fist. And it’s 50 yuan,” or approximately $7.50, went one slogan. For Henan farmers, that sum represented a considerable windfall.

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Chinese officials had embarked on the collection campaign in an effort to keep HIV, which they regarded as a foreigner’s disease, out of the Chinese blood supply. Instead of relying on foreign blood products as HIV/AIDS spread across the United States and other countries, China would harvest its own.

But, as Dr. Wang began to discern in the early 1990s, poor collection practices — as well as government efforts to cover up their consequences — fueled the wild spread of the disease. Among other unsafe methods, blood was drawn from multiple donors and combined. After the plasma was extracted, the remaining mixed blood was reinjected into the donors. If any one donor had HIV, all the others might contract it.

A specialist in hepatitis, Dr. Wang was assigned to a plasma collection station in Zhoukou in 1991. After confirming her suspicions that many donors there were infected with hepatitis C, she implored officials at the site to change the collection prac­tices.

“This will increase cost,” she said she was told.

Undeterred, Dr. Wang took her concerns to the Ministry of Health in Beijing, which began requiring hepatitis C screening for blood plasma donors in 1993, she wrote in an account of her work published on the website China Change in 2012. Officials at the collection site had her removed, but she continued inspecting facilities elsewhere in the region and found similar cross-contamination.

“My own investigation found hepatitis C antibody positive rate to be as high as 84.3%. Being a doctor, I was very anxious,” she wrote. “I knew that hepatitis C and HIV had the same routes of infection. . . . I didn’t want to sit in the office of the Health Bureau waiting for the arrival of an AIDS epidemic. I wanted to directly monitor it and prevent it.”

She was joined in her efforts by Gao Yaojie, an obstetrician-gynecologist from Henan province, also later exiled to the United States, who became one of the country’s most prominent AIDS activists.

“Together the two women started a campaign — Wang behind the scenes with facts and information and Gao out front with a steely resolve and charisma — that shook China’s faith in its health system and government,” Kathleen McLaughlin, a journalist who covered the scandal, wrote in an account published in the London Guardian last year.

Using her own money, Dr. Wang began testing blood samples for HIV and found an infection rate of 13 percent. After she took the samples to Beijing, she found herself frozen out by local and provincial health leaders, who stood to be embarrassed by her revelations. A man she described as a “retired leader of the Health Bureau” came to her testing site and smashed her sign with a baton. When she tried to stop him from destroying her equipment, he struck her.

In 1996, the collection sites were shut down and reopened with HIV testing for donors. “I felt very gratified,” Dr. Wang wrote, “because my work helped to protect the poor.” But she continued to face intimidation. Her clinical testing center was ultimately closed and the utilities cut off, resulting in the loss of all the samples she had collected.

She found work in Beijing before coming to the United States in 2001, the same year that a senior Chinese government official conceded for the first time that the country had a “very serious epidemic of H.I.V.-AIDS” and that coverup efforts by local officials had contributed to its spread. In an interview after Dr. Wang’s death, Wan Yanhai, a prominent Chinese AIDS activist also exiled to the United States, commended her as a health scientist who “took responsibility . . . to tell the truth.”

Zou Shuping was born Oct. 20, 1959, in Fugou County, Henan province. Her mother was a village physician, and her father was a math teacher.

During the Cultural Revolution, Dr. Wang recalled watching her parents be forced to put on dunce caps because her father had been a soldier in the nationalist Kuomintang forces.

She was expelled from school at 8 and was readmitted only after she was adopted by an uncle, who belonged to the Communist Party, and adopted his surname, Wang. She resumed her studies, ultimately earning a medical degree and a PhD, her family said.

Her first marriage, in China to Honghai Geng, ended in divorce amid her whistleblowing campaign. In the United States, she married Christensen in 2005. Besides her husband, of Salt Lake City, survivors include a daughter from her first marriage, Samantha Geng of Tucson; two children from her second marriage, Julie Zou of Bethesda, Md., and David Zou of Salt Lake City; and a brother.

After Dr. Wang’s death, David Cowhig, a retired U.S. Foreign Service officer assigned to the U.S. Embassy in Beijing from 1996 to 2001, wrote on his blog, “Now it can be told: Shuping Wang . . . was also the single most important source” for U.S. officials seeking to understand and curb the HIV epidemic in China.

“She provided rock-solid, highly sensitive internal information about the HIV epidemic and the Chinese leadership’s disappointingly weak response,” he wrote. “That in turn seized the attention of the Clinton White House.”

In the United States, Dr. Wang did medical research in Milwaukee and later at the University of Utah.

“I have since been working over 10 hours every day,” she wrote in her 2012 account of her life. “Hard as it is, I have learned a lot of new technologies and techniques. I am still hoping that, one day, I will be able to apply my experience and skills to serve the Chinese people.”