SIOUX FALLS, S.D. (AP) — A cluster of coronavirus cases at a South Dakota pork plant has highlighted the susceptibility of meat processing workers, who stand shoulder-to-shoulder on the line and congregate in crowded spaces. The Smithfield Foods plant has reported 518 infections in employees and another 126 in people connected to them. Because the workers who slaughter and pack the nation’s meat are vulnerable, so, too, is the supply of that meat. Union leaders wish more had been done sooner at the Smithfield plant. The company says difficulty in getting masks and thermal scanners led to delays in implementing safety measures. But it added hand-sanitizing stations and was scanning employee temperatures before the plant closed.