 Drug users crossed the border into northern Vietnam, where heroin was similarly smuggled in from Myanmar, and shared needles with Vietnamese dealers and users to test purchases before returning to China.Unique to China was the large-scale transmission of HIV through blood donation centers in the early to mid-1990s.The ban on blood product imports from the preceding decade restricted China's blood supply, making blood donation more lucrative, particularly for inadequately funded rural healthcare systems already weakened by privatization.