It emerged during a 2003 Aids outbreak that 10 per cent of people in a random sample tested in Larkana city in Sindh province were infected.
This news moved the country from a "low prevalence - high risk" category to a "concentrated epidemic".
The virus is concentrated among high risk groups - including injecting drug users and sex workers.
There are also a lot of HIV and Aids cases among migrants returning from Gulf states.
While Pakistan’s general rate of HIV is low - at only 0.1 per cent across the general population - the booming sex industry's overlap with high risk groups is likely to make the epidemic spread to the general population. And experts say the crisis is not being properly addressed.
Asim Ashraf discovered that he was HIV positive when he was 18.
He’d taken a compulsory test for people wanting to take the Haj pilgrimage, but he says the doctor was reluctant to break the news.
"I didn't know anything about it,” he told the BBC. “All the ads used to state that Aids was not curable and it's a death sentence - I thought I would die in a couple of days or hours," he says.
Fortunately Asim found a doctor who explained HIV to him and helped him focus on living life as normally as possible. But when he went back to work, Asim was shunned by his colleagues, who refused to sit and eat with him.
After reading up about the condition, Asim is now the HIV-Aids co-ordinator at Rehnuma Family Planning Association. He is married and has a baby daughter and neither she nor his wife is infected.
But there are hardly any Aids awareness campaigns in the country.
"People avoid going to HIV and Aids clinics because there is such a strong stigma around the epidemic," said Jamshed, an HIV-positive UNAIDS worker.
He says "They don't get themselves registered, least of all get themselves tested for HIV because many argue that we are an Islamic country and we do not have this problem," he says.
In Pakistan, the idea that HIV and Aids are caused by "immoral activities” is widely held.
And the worsening security situation there has exaggerated this cultural mind-set, making it harder for groups trying to raise awareness about HIV and Aids. Groups working to fight HIV and Aids in Pakistan have been threatened and have either moved offices or changed their number.
Palvasha, a 30-year-old woman, who is HIV positive said: "We are afraid to hold awareness campaigns because we get accused of spreading wrong and sinful things - so we have to be very tactful."