Rima Himelstein, M.D., an adolescent medicine specialist at Crozer-Keystone Health System, wrote this for the "Healthy Kids" blog, www.philly.com/healthykids.

Remember the big news at the Super Bowl? FBI agents rescued 16 teens from sex trafficking. It was part of the Innocence Lost National Initiative. They were mostly girls 13 to 17; 45 traffickers and their associates from three states were arrested. Big fumble for the traffickers . . . great catch for the FBI.

What is sex trafficking? Sex trafficking, sexual exploitation - same thing. It is the commercial exploitation of children through buying, selling, or trading their sexual services. Individuals under 18 used in commercial sex acts are victims of trafficking, regardless of their willingness or desire to engage in the behaviors, including stripping, prostitution, pornography, and other sexual acts.

Who are the traffickers? Traffickers, pimps - same thing. They are predators who prowl where children are easily found - schools, malls, parks, bus stops, shelters, group homes, and social-media websites - and target the vulnerable ones. They might be strangers . . . or they might be friends, neighbors, or family.

Who are the victims? Kids. The average age at which children are first exploited through sex trafficking is 13. They are not criminals; they're victims. But they're often treated like criminals. FBI data show that 1,200 to 1,600 children were arrested yearly from 1992 to 2009 for prostitution-related offenses. The most vulnerable children are those who have been physically or sexually abused, runaways or homeless kids, and victims of war or social discrimination.

Traffickers are sex offenders. At first, they lure children by giving gifts, compliments, and sexual and physical intimacy, and by promising high-paying jobs. After earning their trust, they use various control tactics, including physical and emotional abuse, sexual assault, confiscation of money, isolation from friends and family, identity stripping, and even assignment of new names. The victims might receive threats of violence against their families. The abusers break the children down emotionally and physically so they become completely dependent. The phenomenon, known as "trauma bonding," results in pathologic loyalty - as in cults, incest, and kidnappings. Child sex-trafficking victims rarely cry for help and will often deny having a trafficker.

It's second only to drug dealing. Estimates are that 100,000 U.S. children are victims of sexual exploitation every year. Of the more than 1.68 million young American runaways each year, an estimated one in seven is a sex-trafficking victim.  And they are here: I-95 enables traffickers to easily move victims up and down the East Coast to large cities.

"It takes a village." We all need to help. Be on the lookout for warning signs:

Chronic episodes of running away.

Homelessness.

Trouble with the law.

Signs of trauma.

Significantly older boyfriend.

Travel with older male (not guardian).

Tattoos that look like a brand of ownership.

Substance abuse.

Contact the National Human Trafficking Resource Center: 1-888-373-7888 or www.traffickingresourcecenter.org.