The world now also knows very well that many refugees and migrants seeking to reach Europe instead find themselves trapped in Libya in slavery-like conditions, and that for women and girls those conditions often involve sexual violence or exploitation.
But what happens to women and girls who manage eventually to escape traffickers and return to Nigeria?
The story of their struggles after they return remains largely untold. It is especially important for International donors to learn what is happening and to help.
Take the case of a woman I will call Adaura C. whom I met in Nigeria while researching this issue. Her tale is tragically familiar.
In 2013, when she was 18, Adaura met a woman who promised her a job as a domestic worker in Libya.
Adaura, struggling with family violence and lack of money in Nigeria, eagerly agreed, but - as is so often the case - soon learned she had been tricked.
After a dangerous journey through the Sahara Desert, witnessing drivers and other men beat and rape women and girls, she arrived in Libya only to find that her local contact was in fact a "madam."
Adaura tried to protest that she'd been hired to do domestic work, but the madam responded: "This is house help."
The madam locked her in a room without food for four days and threatened to kill her. She told Adaura she had to pay off a "debt" of €3,611 to cover travel expenses.
She brought men to have sex with Adaura without condoms. After a month, Adaura discovered she was pregnant; the madam forced her to have an abortion, and charged her for it.
The madam sold Adaura to a Nigerian man in Libya, who also sold her to another man who also sexually exploited her.
She extricated herself from him and moved in with a man who said he would marry her, but she said ISIS abducted them, killed her boyfriend, and only spared her life because she was pregnant.
They took Adaura to an underground prison and forced her to marry a man who raped her.
Three years into this nightmare, Adaura found her way to the International Organisation for Migration, which helped her to return to Nigeria.
New trauma
Adaura's trauma did not end there, however.
Placed in a shelter run by the national anti-trafficking agency, and then in an orphanage because she could not return to her abusive family, she described suffering from physical and mental health problems, and said she felt powerless to rebuild her life and sometimes thought of killing herself.
Support services to address her needs were wholly inadequate. Several months after she escaped her captors in Libya, she still felt like a prisoner and struggled to see a future for herself.
Her plight is not unusual.
Many have sought to escape dire economic situations at home, where jobs are hard to come by.
Some have fled violent conflicts driven in part by climate change and a scramble over scarce resources.
Some have suffered exclusion and discrimination in their home communities that has left them unable to fend for themselves, while others sought to escape abusive families.
Survivors often experience depression, anxiety, insomnia, flashbacks, aches and pains, and other physical ailments, often limiting their ability to work and take part in society.
They struggle to provide financially for their families or even to have money for food or to get health care. For some, their suffering is made worse by families who blame them for the abuses, ostracize them, or complain that they returned without money.
Nigeria has taken some positive steps to address its widespread problem of trafficking, and with support of international development agencies, the country has also established shelters, assisted with medical care, and created skills training and economic support programs for trafficking survivors.
A network of non-governmental organisations provides services to trafficking victims, including shelter accommodation, tracing their families, rehabilitation and reintegration.
Limitations
However, these efforts are all very limited in terms of both the number of people they service and the scope of services they provide.
A key problem is the government's over-reliance on shelters, as opposed to community-based services.
Disturbingly, the Nigerian authorities are actually detaining trafficking survivors in shelters, not allowing them to leave at will. It's a violation of the country's international legal obligations - and re-traumatises women and girls who have already been locked up in horrific conditions by traffickers and captors.
Some survivors in shelters complained about not even being able to receive visitors or contact their families.
Survivors expressed anxiety about not knowing how long they would be in shelters, or if, and when, they would get help finding a way to earn a living.
Women and girls struggling to regain control of their own lives often found that they had no say in what plan was developed for them of what services they were offered.
Nigerian authorities need to do better.
They should ensure that reintegration services, including counseling, medical care, and livelihood support, are long-term and tailored to meet the needs of individual women and girls, and their families.
And of course, they should stop detaining women and girls who have already experienced the horrors of human trafficking.
EU options
International actors also need to step up.
The EU, an important donor to Nigeria, is keen to support border control measures, efforts to raise awareness about human trafficking, and some measures for the reintegration of survivors.
But EU assistance should do more to help survivors recover and rebuild their lives.
Donors should support victim rehabilitation and reintegration services in Nigeria, and this should include more support for national nongovernmental organisations working to assist survivors.
Brussels and member state capitals should ensure that technical assistance to the Nigerian government includes support for expanding community-based reintegration services, including support for girls to resume and complete their education.
Support for safe migration options is also needed.
Trafficking is an international problem.
Many of the trafficking survivors I interviewed had faced abuse in Europe if they got there, or believed they were on their way to Europe when they began their journey.
The EU should commit resource and expertise to helping to heal the physical, mental, social, and economic scars trafficking survivors bring back with them to Nigeria.
