The US Centers for Disease Control and Prevention (CDC) has reiterated a warning that it issued in March against boarding cruiseships, despite allowing the vessels back into US waters.

On 30 October, the CDC issued a Framework for Conditional Sailing Order that lets passengerships sail again in US waters as long as they pass an application process that requires simulated voyages.

"At this time, CDC still recommends avoiding any travel on cruiseships, including river cruises, worldwide, because the risk of Covid-19 on cruiseships is very high," it said, repeating a notice it issued in mid-March when the pandemic first took hold.

"It is especially important that people with an increased risk of severe illness avoid travel on cruise ships, including river cruises."

The CDC said passengers who decide to go on a cruise should get tested three to five days after the voyage and stay home for a week.

"CDC recommends that travelers avoid cruise travel worldwide," it said.

"For most travelers, cruise ship travel is voluntary and should be rescheduled for a future date. "

The CDC recommended several precautions to those who do step on cruiseships, including wearing a mask, washing hands and staying away from infected people.

"If you get sick with Covid-19 symptoms, stay in your cabin and notify the on-board medical center immediately," the CDC said.

Calls to cruise majors Carnival Corp, Royal Caribbean Group and Norwegian Cruise Line Holdings were not immediately returned.

Carnival delays sailings on yet another brand

Carnival has extended suspension of sailing for its P&O Cruises brand to April 2021, having delayed sailings for its North American brands until at least February 2021.

“With hopeful news headlines clearly we do not want to extend our pause in operations any further than absolutely necessary, but given the ever-changing guidance around international travel and the varying regulations in many European ports of call we felt it prudent to cancel these additional dates," president Paul Ludlow said.

“In addition, as the final payments are due for these cruises very soon we felt it was the right thing to do for our guests.

“We are so sorry to disappoint those who were due to travel but really hope they will re-book for later in the year or for our new programme of 2022 holidays which went on sale earlier this month with strong demand, showing great confidence in cruising in the future.”