Hundreds of passengers and crew members on board a Princess Cruises ship fell ill in a single week, according to the Centers for Disease Control and Prevention (CDC).

On the Ruby Princess cruise ship from Texas to Mexico, which departed on February 26 and arrived back on March 5, more than 300 passengers fell ill. Investigators from the CDC claim that 284 of the ship’s 2,881 passengers were unwell.

Thirty-four of the 1,100+ crew members also mentioned feeling sick with vomiting and diarrhea.

The CDC sent a team of epidemiologists and environmental health officials from their Vessel Sanitation Program when the ship berthed in Texas on March 5 to look into the unexplained outbreak.

The cruise ship cleaned and disinfected the ship more frequently than usual in an effort to stay ahead of the infections. Additionally, officials gathered stool samples for CDC examination.

A Princess Cruises spokesperson said that staff members also requested that passengers stay in their rooms. In a statement about the outbreak, the company suggested that norovirus was most likely the cause.

Norovirus causes vomiting and diarrhea and is extremely contagious. Because it causes more than 90% of all diarrhea outbreaks on cruise ships, it is frequently referred to as the “cruise ship virus.”

According to the cruise line, the ship set out on a new journey, a seven-day Caribbean cruise, after a few days. The new passengers were informed about the outbreak by the cruise line company.

It’s not the first time an outbreak on the Ruby Princess has received media attention. In 2020, at the start of the Covid-19 pandemic, the ship berthed in Australia with hundreds of passengers who had tested positive for the virus.

The CDC is examining stool samples to identify what caused the outbreak.