By Jim Kavanagh, CNN

Atlanta, Georgia (CNN) - When Christine Caine talks about human trafficking, she speaks without punctuation, the words and sentences and paragraphs pouring out in a rushing stream that reflects the Australian's passion for rescuing victims and eradicating the crime.

In 2007, Caine, a globe-trotting evangelist and motivational speaker, was walking through the airport in Thessaloniki, Greece, and saw numerous handmade posters with pictures of young women who had disappeared.

"I thought, 'How could you have so many kids missing? How could this be possible?'" she told CNN.

And then someone clued her in: These girls were victims of human trafficking.

"I thought, 'Human trafficking? That doesn't happen, that's ridiculous,'" she said. "Then I went online and did some research, and I was stunned."

Estimates of slave numbers today range from about 10 million to 30 million, according to policymakers, activists, journalists and scholars. (Related: The challenges of counting a hidden population)

And according to the United Nations Office on Drugs and Crime, 79% of human trafficking is sexual exploitation.

Caine recounted witness reports of girls being placed on platforms and sold in auctions reminiscent of the slave trade in the U.S. in the 18th and 19th centuries.

"No human being has the right to buy and sell another human being," she said. "People are not commodities for sale."

In some Greek brothels, Caine said, trafficking victims who get pregnant are smuggled across the border to Bulgaria, where they give birth and the babies are sold into pedophile rings.

"You begin to wonder: How depraved can humanity get?" she said.

But rather than sink into despair, Caine, 44, decided to do something about it.

In 2008 she founded The A21 Campaign, which focuses on sex trafficking in southeastern Europe. The name derives from the goal of "abolishing injustice" in the 21st century. The task seems overwhelming, but the focus is on helping one victim at a time, Caine said.

"The kind of girls we work with are girls that are taken, stolen, brutally raped and then often sold into brothels and forced to service up to 35 or 40 men a day," she said. "They are sold for money, and it's slavery. It's modern-day slavery."

'Why didn't you come sooner?'

She related the ghastly story of a young woman from eastern Russia who was one of 60 girls and women duped by a fake employment agency into signing up for non-existent jobs in the Greek islands.

They were crammed into a shipping container, where half of them died en route to Turkey. The survivors were locked in apartments, where men in police uniforms raped them for days.

The victims were put on tiny boats to take them to Greece, but when the Greek coast guard approached, the traffickers tossed most of the women overboard “like excess baggage,” Caine said. They all drowned, she said.

The traffickers got away with five women, who were forced to work in an Athens brothel. Acting on a tip, Greek authorities raided the brothel and rescued the women.

The Russian woman was brought to The A21 Campaign's shelter the next day. She didn't trust Caine or the staff, thinking they, too, might be slick-talking traffickers. She asked why Caine had gotten involved, and Caine told her how the posters in the airport had prompted her to action.

"I'll never forget how she looked at me and, with tears streaming down her face, she said to me, 'If what you are telling me is true, if you really care about us, then why didn't you come sooner?'" Caine said. She could offer no good answer.

The A21 Campaign has shelters and transition houses in Greece and Ukraine, and plans to open a shelter in Bulgaria, Caine said. Each shelter can accommodate 12 victims, and each house can support a total of 12 victims and staff.

The facilities have a "post-trauma restoration process" in which victims receive medical and psychological care, legal assistance, and vocational and life-skills training aimed at keeping them from being re-trafficked or falling back into the sex trade for lack of options, Caine said.

"I really believe there is a life beyond everyone's past, and there is a hope and a future. And if you commit to the process of restoration, you can overcome the obstacles and hurdles and the pain and the suffering and be made whole," she said.

Although Caine is a prominent preacher with an Australian megachurch, The A21 Campaign is not just for Christians, and the shelter staff doesn't try to convert trafficking victims, she noted.

While few people would publicly endorse human trafficking, we assent to exploitation every day by our consumer choices, Caine said.

"It happens when the world closes their eyes and pretends something isn't happening," she said. “We want a whole lot of goods and services and we don't really want to pay, but it's got to come from somewhere.”

Many products are cheap because they’re made by 5-year-old children working 19-hour days for no pay, she said.

"When you no longer care about the process of how something gets to you but you just want the end result, then you close your eyes to what's going on."

Awareness at the local level

The A21 Campaign has almost 16,000 followers on Twitter, and its Facebook cause has more than 46,000 members. The campaign's website lists 21 things individuals can do to fight trafficking and aid victims. These include buying fair-trade products, volunteering, lobbying politicians, and organizing fundraisers and awareness groups.

One such group is Louisiana State University's Tigers Against Trafficking.

The group's first awareness and fund-raising event was a 5K run; the group's members would have been happy if 10 people had registered but were astonished when it ballooned to 360 participants, said LSU fourth-year law student Natalie LaBorde, who co-founded TAT in 2009.

That first effort raised $10,000 for The A21 Campaign, she said. Other events followed, with about 75 to 100 volunteers working every event, LaBorde said.

"I am so passionate about A21," she said. "I mean, that's like my other family."

LaBorde became involved in the movement while spending a year working with another of Caine's ministries in Australia. She was there when Caine returned after seeing the posters in the airport in Greece and conducted some of the early research that led to The A21 Campaign, she said.

LaBorde returned to Baton Rouge in 2008 with a new mission.

"I knew I had to find a way to connect university students with this incredible cause," she said.

"Our thing is to address trafficking on a global and local level," she said. In addition to A21, Tigers Against Trafficking works with a local group called Trafficking Hope, she said.

Tigers Against Trafficking has helped students establish similar groups at four other colleges, as well as Baton Rouge High School, LaBorde said.

"One of the most exciting things about Tigers Against Trafficking is seeing it live on" after she and the other founders graduate, said LaBorde, who hopes to become a human rights lawyer.

Caine: Don't try to do everything

Caine said she was in court recently for the trial of a trafficker. The judge asked the defendant why he engaged in human trafficking.

"People are so much easier (to traffic) than drugs," the man replied. "The sentencing is a lot less, and you can just kick them and they'll do what you say."

"I can't even believe somebody thinks like that," Caine said. "That's the dark side, that's the evil side. But I think, by and large, most people would think that's very evil and say we've got to stop that from happening.

"My job is to help put tools in people's hands and say, 'Yeah. Together we can stop that from happening.'"

"Often, I think, because we think, 'I can't do it all,' we end up being paralyzed. So we do nothing," said Caine. "But if we understand we can't do everything but we all must do something, and we all find the one thing that we can do, then we'll find that together we will all make such a huge difference and we'll be able to put a stop to this."