Hundreds passengers and crewmembers on two cruise ships were struck with norovirus last week, according to the Centers for Disease Control and Prevention.

On Friday, the CDC reported that more than 600 passengers and crewmembers were struck by the illness on Royal Caribbean’s Explorer of the Seas cruise ship. It was the largest such outbreak reported in the last 20 years.

Explorer of the Seas returned to port two days earlier because of the outbreak. The CDC reported that no specific source had been identified yet.

Also last week, 178 passengers and 11 crewmembers came down with norovirus on Princess Cruise’s Caribbean Princess vessel. The cruise was also cut short due to the illnesses, but the cause was officially reported to be a forecast of dense fog in Houston, the port of call for the cruise, rather than the outbreak.

The cruise ship injury lawyers at Schechter, Shaffer & Harris, L.L.P., Accident & Injury Lawyers help passengers and crewmembers who have been injured or fall ill on cruises.