Kabul, Afghanistan - They tell her not to come. They warn her she'll be killed. But Laila Haidari keeps returning to the same dingy, dangerous underpass, day after day.

It's a scene of abject misery. The Pol-e-Sokhta bridge in Afghanistan's capital Kabul is home to thousands of heroin addicts. They cram together in this small space, living amid raw sewage and human faeces that covers the ground.

Most Afghans watch this horrific scene from the safety of the bridge above, but Haidari ventures beneath. 

A social activist trying to help addicts get clean, she said she's been attacked twice - once so severely she was hospitalised. But Haidari is determined to reverse the toll illicit drugs is taking on her country.

Afghan film-maker Laila Haidari helps heroin addicts and arranges for bodies to be taken away [Steve Chao/Al Jazeera]

"They are human beings and I want to fight for them," Haidari said. "For as long as I'm alive… I will work to help people overcome their addiction."

Her fight is at times overwhelming. Overdoses are common, and it is Haidari who arranges for the dead to be brought to the nearest street for collection by authorities. Sometimes, the bodies are left there for hours.

Most of the heroin produced in Afghanistan is trafficked out of the country, accounting for 90 percent of the world's supply. But increasingly, more Afghans are falling prey to the drug.

A new survey funded by the US Department of State, the results of which were provided exclusively to Al Jazeera, estimates there are an estimated 2.9 million drug users in the country - one of the highest per capita in the world.

A group of Afghan men get high on heroin under a bridge in Kabul [Steve Chao/Al Jazeera]

Ground zero

In the southern countryside of Kandahar and Helmand, Afghanistan's poppy fields are thriving. Poppy produces opium, the main ingredient in heroin.

Along the roadsides, large, dusty government billboards warn against growing the crop. But deeper into the countryside, authorities have little control - and little say on what farmers grow.

Fazel Rehman, a tall, soft-spoken poppy farmer, said he relies on the crop to feed his family of 10.

"Poppy guarantees cash in your hands. We make 10 times more with the drug than other crops," Rehman told Al Jazeera.

"To be honest, I would prefer to grow something else," he said. "But government officials haven't helped us with alternatives. So what choice do I have?"

Farmer Fazel Rehman said growing poppy is the only way to feed his family [Steve Chao/Al Jazeera]

He alleged officials also profit from the trade, saying he paid local police hundreds of dollars recently to leave his fields alone.

Poor farmers such as Rehman see the current fragile truce between the Afghan government and Taliban in the region as an opportunity to make up for lost time.

For more than a decade, NATO troops fought a fierce ground war against the Taliban in these agricultural areas. Markets and crops were destroyed, leaving farmers with few ways to support their families.

The US has pumped $7.6bn in counter-narcotics spending into the country, but the results have been dismal.

Since the 2001 US-led invasion, Afghanistan's drug production has exploded. Poppy cultivation hit 224,000 hectares in 2014 - a record high.  

Police commander Nasrullah Khan inspects a cache of seized opium and heroin [Steve Chao/Al Jazeera] 

Outmatched and outgunned

Just 10km from Rehman's poppy farm, police commander Nasrullah Khan prepared his men for a dangerous raid. For someone given the daunting task of purging the region of opium poppy fields, he seemed resigned to his role.

His squad is a ragtag bunch of regular cops, with some reassigned to drug duty just for the day.

It's a risky task. Khan said his forces came under fire every time they tried to destroy poppy fields in 2014.

"IEDs were exploding around us," Khan said of his last raid. "Many of my officers were injured or killed."

Because of increasing attacks, police were only able to destroy nine of out of an estimated 5,000 hectares of poppy in the area last year.

Afghan police look on as an angry farmer approaches them during an operation to destroy poppy fields [Steve Chao/Al Jazeera]

Back in the capital, federal drug prosecutors face a similar uphill battle, but it's not for a want of funds.

The US and the UK have spent billions to create a clandestine drug court aimed at prosecuting high-level drug traffickers. Al Jazeera gained exclusive access to the court - the first time cameras were allowed inside.

The location is secret and its staff are handpicked and often trained by foreigners.  

All this is supposed to ensure court officials are free from influence and intimidation.

But Najla Temori, a prosecutor of eight years, said this is far from the reality.

"We face extreme danger every day in our jobs," Temori told Al Jazeera. "Twice thugs working for drug lords showed up at my house."

The court has jailed thousands of traffickers, but the real kingpins continue to elude authorities.

Members of Afghanistan's counter-narcotics force say they face daily threats to their lives [Steve Chao/Al Jazeera]

Pointing fingers 

In 2014, authorities did capture and jail Lal Jan, a trafficker who controlled much of the drug trade in southern Afghanistan. He was sentenced to 20 years in jail.

But insiders say he bought his escape by paying off officials with millions of dollars in drug money.

Today, he is nowhere to be found.

Haroon Sherzad, the country's acting minister of counter-narcotics, admits corruption in the justice system is still a problem and cases such as Jan's harm Afghanistan's reputation and chances of securing international aid.

A billboard warns farmers not to grow poppy [Steve Chao/Al Jazeera]

Yet, in explaining why drug production is skyrocketing despite years of efforts and billions of dollars given to the cause, Sherzad pointed the finger back at the international community.

"Their focus was only on terrorism and other sector development, but counter-narcotics was an isolated and marginalised agenda in their programme," Sherzad said.

Hashim Wahdatyar, a representative for the UN Office on Drugs and Crime, said the Afghan government is equally at fault. After President Ashraf Ghani was elected last September, hopes were high that he would list eradicating drugs as a key government goal in his opening remarks.

This was not to be.

"Afghanistan has 22 national priorities, but counter-narcotics is none of them," said Wahdatyar.

Meanwhile, the criminals are becoming bolder.

One smuggler, who asked to remain anonymous, said his gang makes up to $600,000 a year from the trade.

"They'll never stop us," he said. "We've tasted the profits, so we'll never let go."

For more on Afghanistan's drug war, watch 101 East's full film here.

Follow 101 East Senior Presenter Steve Chao on Twitter: @SteveChaoSC

Follow Lois Nam on Twitter: @loisnam