The State Department issued a travel advisory on Sunday urging U.S. citizens not to travel on cruise ships amid fears about the novel coronavirus spreading more rapidly in enclosed spaces. “U.S. citizens, particularly travelers with underlying health conditions, should not travel by cruise ship,” the statement read, while the U.S. Centers for Disease Control and Prevention advised travelers to “defer all cruise ship travel worldwide.” Vice President Mike Pence, however, praised cruise line companies on Saturday, saying that “we want to ensure Americans can continue to enjoy the opportunities of the cruise line industry.” The travel advisory came as the Grand Princess cruise ship confirmed that at least 21 of the roughly 3,500 people on board are infected with the virus. About 1,000 California residents on board the ship are set to be quarantined once it docks in Oakland on Monday. Last month, eight people died and almost 700 people on board the Diamond Princess ship tested positive for the virus in Japan.