Coronavirus cases have been reported on every cruise ship sailing with passengers in U.S. waters.

According to the Centers for Disease Control and Prevention, all 92 ships with passengers have met the threshold for investigation by the public health agency. In every case, the CDC has either started an investigation or has investigated and continues to observe the ship.

The number of ships under investigation had grown sharply in recent days, but it wasn’t until Tuesday’s update, using data submitted by cruise lines Monday, that every ship reached that level.

Last week, the CDC warned all travelers, including those who are vaccinated, to avoid cruise ships. The advice came after the agency said the number of cases skyrocketed from 162 in the first two weeks of December to 5,013 between Dec. 15 and 29.

“The virus that causes COVID-19 spreads easily between people in close quarters on board ships, and the chance of getting COVID-19 on cruise ships is very high, even if you are fully vaccinated and have received a COVID-19 vaccine booster dose,” the agency cautioned.

Cruise lines are requiring all crew and most, if not all, passengers to be fully vaccinated to sail. Passengers also need proof of a recent negative test before boarding.

In addition to the 92 ships with passengers on board, 18 vessels are in U.S. waters with crew only, according to the CDC. Of those, two have met the threshold for investigation, and three have reported cases but not enough to warrant an investigation. Thirteen crew-only ships have reported no cases, according to the data.

“As part of investigating cruise ships that meet the investigation threshold, CDC will obtain additional information from the cruise ship, such as case exposure histories, details about close contacts, traveler vaccination rates, and medical capacities,” CDC spokeswoman Caitlin Shockey said in an email.

She said the agency would work closely with cruise lines and “consider multiple factors” before moving ships from their current status — yellow — to the more serious red status, in which a ship would return to port right away or delay a sailing. To reach that mark, a ship must have sustained transmission of covid-19 or covid-like illness and the potential for “cases to overwhelm on board medical center resources,” the CDC says.

Since late December, several cruises have been turned away from ports because of passengers or crew on board testing positive. Most have continued on their journeys, even when they were forced to skip the stops they had planned.

On Wednesday, however, Norwegian Cruise Line confirmed it was canceling a nine-day Caribbean voyage on Norwegian Getaway that was scheduled to leave Miami that day. The reason, according to the cruise line: “COVID related circumstances.”

The operator gave the same reason on Tuesday for bringing a ship, Norwegian Pearl, back to Miami after it left for an 11-night Panama Canal trip Monday. According to the Miami Herald, passengers were informed that the trip was ending after an unspecified number of crew tested positive; the company would not provide that number to The Washington Post. The vessel is scheduled to return to Miami on Thursday.

“We will never compromise on health and safety and we will of course, continue to take all appropriate action to ensure everyone’s well-being and to protect public health,” the company said in a statement.