The Centers for Disease Control and Prevention extended its “No Sail Order” for all cruise ships by at least 100 days — or until Covid-19 is no longer considered a public health emergency.

The CDC said there are 100 cruise ships at sea off U.S. coasts, with 80,000 crew members on board. Twenty ships at port or anchorage in the U.S. have known or suspected Covid-19 among crew, according to the agency’s statement Thursday.

The industry suspended operations in mid-March after a series of dramatic coronavirus outbreaks raised questions about the safety of cruising. Some ships caught at sea at the time have struggled to find ports to welcome them back, though all but at handful have now done so.