Louisiana was quickly becoming another smoldering hotspot. The number of new cases there jumped by more than 500 Thursday, for a total of over 2,300, with 86 deaths, including a 17-year-old, the health department said. The higher infection numbers reflected an increase in testing. New Orleans was gearing up for a possible overflow at hospitals, with plans to treat as many as 3,000 patients at the city’s convention center.