Gao Yaojie, a renowned dissident doctor who exposed the Aids epidemic in rural China, has died aged 95.

Dr Gao died of natural causes in New York, where she had been in exile since 2009, a friend of hers told the BBC.

Her work uncovered how businesses selling blood led to the spread of HIV in the countryside.

She was at the forefront of Aids activism in China and travelled across the country treating patients, often at her own expense.

Born in Shandong province in 1927, she and her family fled to the central Henan province during World War Two.

A gynaecologist by training, she encountered her first Aids patient in the central province of Henan in 1996.

In the 1980s and 1990s, selling blood was common in rural areas such as Henan. Limited economic opportunities among farming communities left them with few other options to make a living - and blood-selling was often backed by local governments. But with few cases of HIV being diagnosed in rural China at the time, and low awareness of Aids, blood was also collected from HIV+ patients, leading to the spread of the disease.

At the time, Chinese authorities thought that HIV was transmitted in either of two ways - through sex or from mother-to-child during pregnancy. Dr Gao had an epiphany when she discovered that one of her patients did not fall into either category but had a history of blood transfusion.

Known as "Grandma Gao", she visited villages in Henan to investigate the scale of Aids cases. She reportedly visited more than 100 "Aids villages" and met more than 1,000 families. She often gave away food, clothes and printed resources on Aids, - mostly at her own expense.

Henan officials initially covered up the blood-selling practice, but eventually shut the businesses down in the mid-1990s. But Dr Gao kept speaking up about the spread of HIV in the country.

"It's bigger. It's nationwide, everywhere. I have seen everything with my own eyes. Blood selling is illegal. In the past, it was open and public. Now, it's underground," she said in an interview with the BBC in 2010.

Dr Gao had claimed that 10 million people were infected with HIV in China, far greater than Beijing's official figure of 740,000. But this was disputed by officials.

While she was not the first Chinese doctor to expose the AIDS epidemic, it was her efforts that made the situation known to the country and beyond.

"After Dr. Gao failed to bring the problem of Aids spread by blood purchase stations to the attention of the Henan provincial government, she brought the story to a reporter for the New York Times," said Professor Andrew Nathan at Columbia university, who helped her to settle in New York. "The story of the Henan blood-sales Aids epidemic (was) on the front page of the newspaper, and it became an international scandal, which then influenced the Chinese government to do something about it."

This led to more media coverage of Dr Gao's findings in the early 2000s. She also received numerous domestic and international awards.

Chinese authorities were initially lenient with her. State broadcaster CCTV extolled her as one of the "figures that moved China" in 2003, and praised her "profound knowledge and rational thinking which dispelled people's prejudices and fears, and her mother-like love and selfless enthusiasm that warmed the helplessness of the vulnerable".

Former US Secretary of State Hillary Clinton said Dr Gao was "simply one of the bravest people I know".

But Henan authorities later grew uncomfortable with her criticism of officials. She left China in 2009, in the face of surveillance and growing pressure from the local government.

She moved to New York and lived there until her death.Her husband Guo Mingjiu died in 2006. She is survived by two daughters and a son.

Despite being celebrated for her work as a doctor, Dr Gao was estranged from her children.

Her eldest daughter once said their mother "saved other people but destroyed our family", according to Shiyu Lin, author of The Oral History of Gao Yaojie.

"Even Grandma Gao herself once told me: I was a good doctor, but not a good mother," Ms Lin recalled.

Although she was long absent from China, her death has been mourned by some Chinese netizens.

"She was a great figure. But young people nowadays may not know about that history," said one user on social media platform Weibo.

"Our generation of news workers or news readers know her and remember her. It [the news] also reminded me of other Chinese doctors' names such as Jiang Yanyong and Li Wenliang," said Chinese journalist Li Weiao on Weibo, referring to the whistleblowers of the Sars outbreak of 2003 and the Covid pandemic respectively.