For more than a week, Koné, a young Ivorian, has had no news of his half-sister. All he knows is that 15-year-old Mariam is being held hostage by other migrants in Sfax, Tunisia’s second largest city. Mariam is not alone. Since October, there have been worrying reports of a new form of trafficking in the country. Sub-Saharan migrants of various nationalities are being kidnapped and…



