WASHINGTON (XINHUA) - The United States Centres for Disease Control and Prevention (CDC) on Saturday (Nov 21) advised against cruise ship travel, as the risk of Covid-19 on liners is very high.

"For most travellers, cruise ship travel is voluntary and should be rescheduled for a future date," the CDC said in a statement on its website.

The agency raised its warning to Level 4 from Level 3, citing "very high" risk of Covid-19 on cruise ships. It also advised liner passengers to get tested three to four days after the travel and stay at home for seven days, even with negative test results.

In March, the CDC issued a no-sail order in response to the Covid-19 pandemic. Last month, the agency came up with a framework for a phased resumption of liner operations. Every ship must be certified by the CDC before travellers can board.

According to the CDC, from March 1 to Sept 28, there were "a total of 3,689 confirmed cases of Covid-19 or Covid-like illness cases on cruise ships and 412 deaths".