The U.S. Centers for Disease Control and Prevention has announced that an unknown illness sickened several people aboard a cruise ship earlier this month.

The mystery gastrointestinal illness broke out onboard the Navigator of the Seas, a Royal Caribbean ship, on a round-trip to from the US to Mexico. Some 134 of the 3,914 guests fell ill, along with 11 crew members. Symptoms included sickness, abdominal cramps and diarrhoea.

A dream vacation quickly turned into a nightmare for more than 140 people aboard Royal Caribbean’s Navigator of the Seas when a mysterious illness swept through the ship during a week-long cruise.The gastrointestinal outbreak,