If the pandemic’s first wave burned through dense metro hubs such as New York City, Chicago and Detroit, the highest percentages of new cases are coming from places with much smaller populations: Lincoln County, Ore., an area of less than 50,000, has averaged 20 new daily cases; the Bear River Health District in northern Utah has averaged 78 new cases a day in the past week, most of them tied to an outbreak at a meat processing plant in the small town of Hyrum.