Learn more about outbreaks of gastrointestinal (GI) illness on cruise ships in the Vessel Sanitation Program’s (VSP) jurisdiction, including outbreak details and actions taken in response.
Posting outbreaks
We post outbreaks when they meet both of the following:
- Ship is under VSP jurisdiction (on voyages including both U.S. and foreign ports)
- Voyage has 3% or more of passengers or crew reporting symptoms of GI illness to the ship’s medical staff
We may also post other outbreaks of public health significance.
Tracking illnesses
GI illness is a commonly used term for acute gastroenteritis (AGE). Reporting GI illness on cruise ships is important. When passengers and crew tell the medical center onboard about their symptoms, it helps GI outbreaks get detected quickly. This allows steps to be taken to limit the spread of illness. Medical staff evaluate symptoms to see if they meet our case definition for AGE:
- Three or more loose stools within a 24-hour period or what is more than normal for that person OR
- Vomiting along with one of the following symptoms: diarrhea, muscle ache, headache, abdominal cramp, or fever
Cruise ships are required to report these cases to us.
Finding causative agents
Norovirus is often a cause of GI outbreaks on cruise ships, but we don’t always know the cause of the outbreak when we begin an investigation. Finding the agent that caused an outbreak (causative agent) can take time. When an outbreak occurs, people whose symptoms met the case definition are asked to provide stool or vomitus samples. These samples are tested to determine the causative agent.
Sometimes we can’t determine the causative agent. Reasons can include:
- People whose symptoms met the case definition did not provide samples
- Symptoms started after a voyage ended
Content Source:
National Center for Environmental Health
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