Probability of Getting Sick on a Cruise

The CDC's Vessel Sanitation Program tracks gastrointestinal illness (GI) on cruise ships. On average, about 2% of passengers (20 per 1,000) experience GI illness during a cruise voyage. Norovirus is the most common cause, responsible for about 90% of reported outbreaks on cruise ships.

The CDC defines an outbreak as when 3% or more of passengers or crew report GI illness. While outbreaks receive significant media attention, they are relatively uncommon: only about 10-15 outbreaks are reported per year across all cruise ships visiting US ports, out of thousands of voyages carrying millions of passengers.

The confined environment of cruise ships facilitates disease transmission through contaminated surfaces, buffet-style dining, and close contact with large numbers of people. Prevention measures include frequent hand washing with soap and water (hand sanitizer is less effective against norovirus), avoiding the buffet if ill passengers are reported, and reporting illness promptly to the ship's medical center. The CDC's Green Sheet Program rates cruise ships on sanitation, and most major cruise lines now score above 90 out of 100.