A few of Smithfield Foods' massive pork-processing plants turned into Covid-19 hotspots soon after the virus reached the United States. Employees at the plants typically work in conditions that make it easy for the virus to spread: close quarters, cool temperatures, and constant air circulation. Social distancing measures are hard to implement without slowing down operations.  By mid-April, employees of Smithfield’s Sioux Falls, South Dakota,  plant accounted for half of its count