By Hannah Sampson
The Centers for Disease Control and Prevention said Thursday that all travelers - even those who are vaccinated - should avoid cruises.
In a statement, the agency said cruise lines reported 5,013 coronavirus cases on ships operating in U.S. waters between Dec. 15 and 29, a massive increase from the 162 cases reported over the prior two weeks.
The CDC escalated the travel health notice for cruising from Level 3 to 4, its highest. Previously, the agency advised that people who were not fully vaccinated or those at increased risk of severe illness should not cruise.
"This reflects increases in cases onboard cruise ships since identification of the Omicron variant," the CDC said on its website.
The agency last lowered its warning from Level 4 to Level 3 on June 17.
The update comes as 91 ships carrying passengers from U.S. waters have reported cases over the past seven days and met the threshold for CDC investigation, according to a tally updated Thursday using data submitted by cruise lines.
"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 said in its warning.
Cruise lines have turned to vaccine requirements to create what the industry promotes as a safe haven at sea.
Most operators require everyone 12 and older to be fully vaccinated before they board - though some also mandate vaccines for those as young as 5 - and everyone who takes a cruise must test negative.
As the Omicron variant has fueled surges worldwide, ships have also added rules requiring everyone to wear a mask indoors unless eating or drinking, a requirement that had previously been limited to crowded areas or unvaccinated passengers.
On recent trips, some ports have refused to let ships with sick people on board dock.
In a statement, the Cruise Lines International Association called the CDC's update "particularly perplexing considering that cases identified on cruise ships consistently make up a very slim minority of the total population onboard" and that most cases are mild or asymptomatic.
The cruise industry administers nearly 10 million tests a week in the US, the group said.
"While we are disappointed and disagree with the decision to single out the cruise industry - an industry that continues to go above and beyond compared to other sectors - CLIA and our ocean-going cruise line members remain committed to working collaboratively with the CDC in the interest of public health and safety," the statement said.
The CDC's conditional sailing order, which lays out the rules for cruises during the pandemic, will expire on Jan. 15.
After that, CDC spokeswoman Caitlin Shockey said in an email, the agency "intends to transition to a voluntary program, in coordination with cruise ship operators and other stakeholders, to assist the cruise ship industry to detect, mitigate, and control the spread of Covid-19 onboard cruise ships."
Despite the CDC's warning Thursday - and a plea from one U.S. senator this week - cruise lines show no signs of shutting down. In the earliest days of the pandemic, when ports refused ships as passengers became ill and died, the industry halted operations.
Ships did not start sailing again in the U.S. until late June, more than 15 months after the shutdown.
The coronavirus broke through precautionary measures even in the earliest days of the comeback, though the number of cases was far lower.
From late June to late October, cruise lines confirmed 1 359 cases on ships sailing in US waters, according to the CDC.
The markedly higher number of recent infections has so far resulted in relatively mild cases, according to cruise companies.
"Our case count has spiked, but the level of severity is significantly milder," Calvin Johnson, chief medical officer at Royal Caribbean Group, said in a business update Thursday. "We will remain nimble and in constant contact with health authorities."
The company said the highly transmissible new variant had delivered a blow to business, with a drop in bookings and higher number of short-term cancellations.
But the company said bookings for the second half of 2022 showed "strong demand from the critical U.S. market."
"We are constantly learning and adjusting as Omicron appears to be ushering in a new phase in the fight against Covid-19," Royal Caribbean Group CEO Richard Fain said in the update.
"We expect these factors to have a negative impact in the short term but are optimistic they will lead us to a more pervasive but less severe health environment."