Guinea-Bissau, one of the world's poorest nations, has become a major transshipment hub and the epicenter in Africa for the cocaine trade, according to U.S., European and U.N. officials. The shift demonstrates how the flow of drugs adapts not only to law enforcement pressure but also to the forces of global economics. Officials said some of the world's richest criminal gangs are exploiting barely functioning countries such as Guinea-Bissau, which has 63 federal police officers, no prison and a population that still lives largely in thatched-roof homes on dirt roads with no electricity or running water. The Colombian cartels are responding to the pressure for cocaine in nations such as Britain, Spain and Italy, where demand is soaring as the U.S. market has leveled off, officials said. Antonio Maria Costa, executive director of the U.N. Office on Drugs and Crime, described the strong currencies in Europe, where cocaine sells for twice as much as in the United States, as "a magnet" for the cartels. Police raids in Colombia are increasingly turning up suitcases full of euros instead of the traditional dollars. "West Africa is under attack," said Costa, who recently visited Guinea-Bissau and concluded that it is so overrun by the cocaine trade that it could become Africa's first "narco-state."