The Centers for Disease Control (CDC) reports numerous outbreaks of norovirus on cruise ships operated by Celebrity Cruises, Cunard, Holland American Lines, and Royal Caribbean.
Every time there is an outbreak, the cruise lines blame the passengers who board the cruise ships. The media picks up in this theme and often reports that the problem is not with the cruise ships but the passengers who board the ships already infected with norovirus. For example, in a recent article in the New York Times Travel Section "Stomach Bug Hits Cruise Ships," respected journalist Michelle Higgins writes " . . . the contaminated ships have since been disinfected . . . but such measures can’t prevent a sick passenger from coming aboard and infecting others." Ms. Higgins suggests that " the best defense is simple: wash your hands."
Unfortunately, the issue is not so simple.
According to the U.S. Food and Drug Administration (FDA), whereas "person to person" transmission of norovirus has been documented, "norwalk gastroenteritis is transmitted by the fecal-oral route via contaminated water and foods."
Contaminated Water Supplies On Cruise Ships?
The FDA indicates that contaminated water is one of the most likely causes of norovirus. The FDA reports that "water is the most common source of outbreaks and may include water from municipal supplies, well, recreational lakes, swimming pools, and water stored aboard cruise ships.
So whereas you always hear reports of extra cleaning of the bathrooms and cabins on infected cruise ships, there is never a mention of whether the potable water is tested and the results of the testing.
Contaminated Food Supplies On Cruise Ships?
In addition to water supplies on cruise ships being a potential source of the virus, food supplies on cruise ships can also sicken the passengers.
The FDA reports that "shellfish and salad ingredients are the foods most often implicated in norwalk outbreaks. Ingestion of raw or insufficiently steamed clams and oysters poses a high risk for infection with Norwalk virus. Foods other than shellfish are contaminated by ill food handlers."
It would be interesting to determine the job positions of the crew members infected with norovirus. For example, the CDC reports that sixty-nine crew members were reported ill on Celebrity's Mercury and Millennium cruise ships during recent cruises. How many of these crewmembers were cooks, waiters or food handlers?
The issue of eating oysters and other shellfish on cruise ships presents a double whammy. Cruise ships dump sewage 12 miles from shore, and the fecal material can contaminate shellfish which filter-feed. Both cruise passengers and people ashore can then be infected by eating contaminated shellfish.
Uncertainty Regarding Cause of Virus and Transmitting Agent
Although the CDC tries to determine the "causative agent" of the outbreak, this means that they are trying to determine the nature of the pathogen (i.e., whether it is norovirus or some other virus). But the CDC does not report whether the virus came from a person boarding the cruise ship or, the more likely scenario if the FDA is correct, from contaminated food and water on the cruise ship.
The issue arises where do the cruise lines obtain their potable water? From U.S. based vendors or from the Caribbean islands? What testing is done at the ports before the water is brought aboard? Where do the food products come from? Is any of the food inspected by the FDA before it is loaded on the cruise ships?
The CDC reports that around 600 passengers became ill on Celebrity's Mercury cruise ship on the last two cruises alone. Are we to believe that all 600 people simply failed to wash their hands? Or is there something in the food and water?
Cruise lines should be required to publicly report the test results of the cruise ship's water samples, so that the U.S. public can determine the true cause of cruise ship illnesses.
If contaminated water is the culprit, all of the external cleaning of cruise ship surfaces is not going to solve the problem.
Passengers can track the reported outbreaks on the CDC web page which tracks "Outbreak Updates for International Cruise Ships." Not all norovirus outbreaks are required to be reported to the CDC and the CDC website is incomplete.