COVID cases onboard cruise ships are surging, according to the Centers for Disease Control and Prevention Director Dr. Rochelle Walensky.

Walensky said that over the past two weeks, the agency has seen a 30-fold increase in COVID-19 cases on cruise ships due to the highly contagious Omicron variant.

Walensky made the comments during a Senate hearing on Tuesday. She did not provide further details on how many COVID cases were actually being reported on cruise ships to date.

But the CDC has confirmed that cruise ships in U.S. waters had 162 COVID cases in the first two weeks of December, which increased rapidly to approximately 5,000 virus cases from Dec. 15 to Dec. 29 amid the Omicron spread, according to the agency, CNBC reported.

On Tuesday, the CDC said that the Omicron variant now accounts for 98% of all COVID-19 cases in the U.S.

The CDC has placed cruise ships on its highest warning category for travel – Level 4 “very high” risk – saying that “ 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 CDC warning for cruise ships is for all travelers regardless of vaccination status, despite most cruise lines requiring passengers and crewmembers to be fully vaccinated to board vessels, in addition to having a negative COVID test.

Most cruise ships in U.S. waters have been operating under the CDC’s conditional sailing order, which mandates certain safety protocols for ships. The order, which was put into effect in October 2020, is set to expire on Jan. 15.

Walensky said during the Senate hearing that she doesn’t believe the order will be renewed but continued by saying that the CDC does expect the order to become a voluntary program for cruise lines.

She said she hoped “the cruise ship industries will continue to understand that this is a really safe practice for those industries.”

But Walensky did not have any near-term predictions for the cruise industry, saying, “What I can’t predict is what the summer will bring.”

The luxury cruise ship MSC Preziosa, seen at anchor in  Rio de Janeiro on November 26, 2014, is one of three big cruise ships to see Covid outbreaks in late 2021 or the early days of 2022
The luxury cruise ship MSC Preziosa, seen at anchor in Rio de Janeiro on November 26, 2014, is one of three big cruise ships to see Covid outbreaks in late 2021 or the early days of 2022 AFP / YASUYOSHI CHIBA