One of the fastest growing Aids problems in China is hidden from view in the far north-western province of Xinjiang.
Xinjiang sits at the crossroads of ancient trade routes like the old silk road which bore caravans of silk and spices to central Asia.
Now juggernauts shuttle across from Pakistan and Afghanistan, and north from the Golden Triangle bearing a modern commodity - heroin, and with it deadly disease - Aids.
Aids and sexual diseases are stigmatised in much of China
Zhang Shun has seen eight friends die of Aids. A former drug user, he has asked for his name to be changed.
Many of Xinjiang's drug users are ethnic Uighurs. Unemployed and poverty stricken, they take drugs because they fear they have no future. And now Aids is cutting a swathe through this community. The first case of HIV was diagnosed in Xinjiang in 1996.
By the end of September this year, there were 7,893 reported cases. But officials estimate the real figure to be between 20,000 and 60,000, and tests in government detoxification centres indicate around 70% of intravenous drug users to be HIV positive.
Zhang Shun suspected he was an HIV carrier after his blood was tested twice in a detox centre. But he says no-one told him the test results.
"After I came out of the detox centre, I asked them why they checked my blood twice and didn't tell me the results. They said, 'You didn't pay for your own test, the state paid for you, so we can't tell you the results. You're just a subject in our experimental testing programme.'"
So he paid for a third blood test, which confirmed his fears. But he says many others do not want to know their HIV status and are not willing to change their risky behaviour.
Mawlam Mamtimin, a Uighur outreach worker with a US-funded project tracking drug users to see if they become HIV positive, agreed.
"They know that it's dangerous to share injecting equipment," he said. "But they can't stop. Drug users often indulge in risky behaviour. For example they often change sexual partners, and very seldom use condoms. So we give them condoms as part of the programme."
Many simply do not know how to protect themselves. Twenty-one year old Fatima was infected by her boyfriend, a drug user. She knew he was HIV positive, but did not realise that using condoms would protect her.
"We Uighur people don't know about these kinds of things," she said. "We don't know how Aids is passed."
For some in Xinjiang, life - and sex - is cheap
And sex, like drugs, is also an industry here. Many of the smart skyscrapers in the city of Urumqi house karaoke bars. And the girls at those bars often provide extra services - condoms optional.
Just outside the city, a row of one-storey huts serves as a roadside brothel, where passing truckers stop for sex. It is at places like these that China's Aids epidemic could gain momentum.
"If you wash after sex, it disinfects you," one Uighur sex worker told me. "Then you won't get so many women's diseases."
She became a prostitute to support her family after her husband died in accident. Now she makes her living having sex with men for $12 a time. She may end up paying for her ignorance with her life. And she is not the only one.
Even some medical professionals are badly informed. In one backstreet clinic, a Uighur doctor told me: "There's no Aids in Xinjiang. None at all."
When I asked him what the symptoms were, he said: "Headache, heart pain, it's like having a cold."
His ignorance was shocking, but hardly surprisingly. Medical students here only get two hours of lessons about Aids.
The local health bureau admits it is struggling to deal with HIV/Aids. Deputy director Wang Shaohua says there are no functioning Aids wards, no Aids specialists and no anti-retroviral drugs in Xinjiang.
"In my opinion, our main problem isn't just one of resources," he says. "From the point of view of technology and capabilities, we're extremely weak. Even if you gave us money we wouldn't know how to spend it. We're really lacking in experience."
What this means is that even some doctors and nurses are scared of Aids. So people with HIV - already shunned by society - are sometimes also turned away from hospitals where they seek treatment.
HIV carrier Zhang Shun described what happened when he fell ill.
"Last year I got sick, I got pancreatitis," he said. "I went to the hospital and I hid my HIV status. But the doctor suspected me, so he did an HIV test and found out my status. Then the hospital turned me away. If I get sick again, I won't go back to hospital."
There are, however, signs of change. The fact that government officials agreed to be interviewed on Aids in Xinjiang signals a new openness. International agencies and non-governmental organisations are running projects in Xinjiang educating healthcare professionals, officials and schoolchildren about the disease. And HIV carriers like Zhang Shun are encouraged that the central government has pledged to provide free anti-retroviral treatment for poor people.
But education is a slow process, and the free treatment will be rolled out over a period of several years. In the meantime, life for HIV carriers in Xinjiang is characterised by stigma, discrimination and fear.