There are 27 million people serving as literal slaves around the world, and every year 600,000 to 800,000 victims are trafficked across international borders, half of whom are children.

This 9.5-billion-dollar a year industry is hardly limited to the developing world, with 14,500 to 17,500 victims trafficked into the United States every year, according to the U.S. State Department.

"We have to make sure that when we are talking about child trafficking that we include the U.S. victims," says Rachel Lloyd, a survivor of child slavery and founder of Girls Educational and Mentoring Services.

"We have to acknowledge that all children are worthy of the same dignity and respect and that we don't make that distinction within our own judgment and policies and within our services," she said.

At a recent meeting on child slavery by Media 4 Humanity at the Harvard Club, panelists said that teenage girls have been bought and sold on both the Internet auction site E-Bay and the popular classified forum Craig's List.

New York, California, Florida and Texas have the highest rates of slavery in the U.S., and close to 300,000 U.S. boys and girls are at risk of falling into the sex trade.

"Slavery has returned to American soil," said Steve Wagner, the director of the human trafficking programme at the U.S. Department of Health and Human Services.

Wagner added that the estimated number of trafficking victims in the U.S. -- 50,000 -- is most likely much greater. It is assumed that one-third are children.

"In the U.S., victims of human trafficking will not self-report, this makes it unlike virtually any other category of major crime," he said.

In October 2000, the U.S. passed the Trafficking Victims Protection Act (TVPA) to prevent human trafficking overseas, increase prosecution of human traffickers in the United States, and protect victims and provide them with federal and state assistance. Before the TVPA, no federal law existed in the U.S. to protect victims, so many were treated like illegal immigrants under state legislation.

While women and children are particularly vulnerable to trafficking for the sex trade, human trafficking is not limited to sexual exploitation. It also includes people who are forced into marriage or into bonded labour markets, such as sweatshops, agricultural plantations and domestic service.

The spread of HIV/AIDS among victims trafficked into prostitution also makes victim support and repatriation a public health issue. The U.S. government believes there is a link between trafficking in persons and HIV/AIDS, and it has developed programmes to address both, such as rehabilitation efforts for victims of sex trafficking and education about the public health implications of trafficking.

Trafficking is fostered largely by social and economic disparities that create a supply of victims seeking to migrate and a demand for sexual and other services that provide the economic reward for trafficking.

Experts say preventing human trafficking requires several strategies. Criminal punishment is an important element, but addressing the underlying conditions that drive both supply and demand are also necessary. It is also critical to make the socially marginalised groups from whom victims are most often recruited more aware of the reality of trafficking and less likely to be deceived when approached by traffickers.

Trafficking in persons may resemble the smuggling of migrants, but there are several important differences. The smuggling of migrants involves migrants who have consented to the smuggling.

Trafficking victims, on the other hand, have either never consented or, if they initially consented, that consent has been rendered meaningless by the coercive, deceptive or abusive actions of the traffickers, experts say. Smuggling is always transnational, whereas trafficking may not be.

Another difference is that smuggling ends with the arrival of the migrants at their destination, whereas trafficking involves the ongoing exploitation of the victims in some manner to generate illicit profits for the traffickers.

The Global Programme Against Trafficking in Human Beings was designed by the U.N. Office on Drugs and Crime (UNODC) in collaboration with the United Nations Interregional Crime and Justice Research Institute and launched in March 1999.

Activities carried out in cooperation with the national counterparts are based on the assessment of the involvement of organised crime in the trafficking of human beings. On a national level, it aims to create awareness, train law enforcement officers and advise on drafting and revising on relevant legislation.

At the international level, UNODC is establishing a database of effective anti-trafficking strategies that can be used by policymakers, researchers and the NGO community.

"It is not enough to keep providing services," notes Florrie Burke, senior director of international programmes for Safe Horizon, a New York-based non-profit victim assistance organisation. "We need to stop the crime of human trafficking."