Shares of cruise operators fell Wednesday, after the number of ships being investigated and observed by the Centers for Disease Control and Prevention as a result of COVID-19 cases reported has increased, fueling fears that the CDC could call for another pause in sailings. Shares of Carnival Corp. CCL, -0.71% dropped 0.9% in premarket trading, Norwegian Cruise Line Holdings Ltd. NCLH, -0.46% slid 1.4% and Royal Caribbean Group RCL, +0.08% slumped 1.1%. Meanwhile, futures ES00, for the S&P 500 SPX, +0.14% slipped less than 0.1% ahead of the open. The CDC said as of Dec. 28, the number of Carnival ships that have reached “yellow” status, which indicates reported cases of COVID-19 have met the threshold for investigation, rose to 32 from 25 on Tuesday. For Norwegian, the number of “yellow” status ships rose to 15 from 12, while the number of Royal Caribbean’s “yellow” status ships grew to 25 from 20.