Despite issuing a Conditional Framework for cruise lines to return to operations at the end of October, the U.S. Centers for Disease Control (CDC) raised its warning to avoid going on any cruise ship on Saturday to Level 4.

Upped from Level 3, the new Level 4 warning means a “very high level of COVID-19.”

“CDC recommends that all people avoid travel on cruise ships, including river cruises, worldwide, because the risk of COVID-19 on cruise ships is very high. It is especially important that people with an increased risk of severe illness avoid travel on cruise ships, including river cruises,” the agency said, in a statement on its website.

The CDC said that passengers who decide to go on a cruise should get tested three to five days after their trip and stay home for seven days after travel.

The CDC said that even if someone tests negative, they should stay home for the full seven days.

The CDC also said if a guest doesn’t get tested, it’s safest to stay home for 14 days after travel.