As the global death of Covid-19 nears 400,000, U.S. health officials are keeping a close eye on caseloads and hospitalization rates as states continue to relax their lockdown measures and reopen different types of businesses. U.S. cases have been climbing since Memorial Day, but New York City this week reached an optimistic milestone: on Friday, the city, the epicenter of the U.S. outbreak, reported zero coronavirus death for the day. That hasn't happened since March.