The Centers for Disease Control raised its warning level just weeks after it lifted its months-long ban on cruise ships operating from US ports.
The CDC says the warning also includes river cruises and applies worldwide.
And they also warned travellers with “increased risk for severe illness” to avoid cruises.
Anyone who does board a cruise ship should get tested three to five days after the trip and isolate at home for seven days regardless of the result, says the CDC.
And they advise travellers who do not get tested to isolate for 14 days.
Most major cruise lines had already cancelled trips through 2020 but there had been hope they could begin again in earnest next year.
Despite the “no-sail” order being lifted at the end of October cruise operators now have to go through a string of detailed steps before they can begin voyages again.
These include crew testing and “simulated voyages” to test “real world onboard conditions of cruising.”
Earlier this month SeaDream 1 became the first ship to leave from a Caribbean port since the pandemic began.
Despite pre-boarding testing the ship was hit with seven positive tests after one passenger fell ill and had to return to Barbados.
That ship was operating outside of US waters and did not have to follow CDC guidelines.
Despite the virus cruise line Royal Caribbean has been inundated with interest from passengers.
Michael Bayley, president and CEO of Royal Caribbean, said on Facebook that 100,000 people had registered interest in a “mock cruise."