Seven days before Japan quarantined a cruise ship near Tokyo early this year, in what became one of the first coronavirus hot spots outside China, another cruise ship docked in southern Japan.For the next five weeks, as the virus took hold in Japan and the Diamond Princess in Yokohama port grabbed global attention, the Japanese authorities issued no warnings to the Costa Atlantica 1,200 km (750 miles) to the southwest.Passengers from the Yokohama ship were dying while people from the other vessel freely got on and off…