Tag Archives: norovirus

5.5 Million Cases of Norovirus are Spread Via Food Each Year

By Kim Smiley

Norovirus outbreaks on cruise ships may make exciting headlines, but the reality is that only one percent of norovirus outbreaks occur on the high seas.  About 20 million people in the US are sickened by noroviruses in the US each year and one of the most common transmission paths is via food.  Food-borne norovirus is estimated to be responsible for 5.5 million cases of norovirus annually in the US.

A Cause Map, a visual method for performing a root cause analysis, can be used to analyze this issue.  The first step in the Cause Mapping process is to determine how an issue impacts the overall goals and then the Cause Map is built by asking “why” questions to visually lay out the cause-and-effect relationships.  In this example, we’ll focus on the safety goal since it is clearly impacted by 5.5 million cases of norovirus transmitted via food.

So why are people getting norovirus from food?  This is happening because they are consuming contaminated food, predominantly at restaurants or catered events.  The food becomes contaminated when a food worker’s hands are contaminated by norovirus and they touch food, particularly food that is ready to serve and won’t be cooked prior to consumption.  (Disclaimer: You may want to stop reading here if you are eating or thinking about going to out to eat soon.)

For those unfamiliar with the illness, norovirus is basically a gastrointestinal nightmare that can cause the human body to do very messy things.  If a food service worker is ill, the virus can get on their hands, especially after using the bathroom.  According to a Centers for Disease Control and Prevention (CDC) report, the transmission of food-borne norovirus is “primarily via the fecal-oral route.”  And that is more than enough said about that.

It is also worth asking why food workers are at work if they are under the weather.  In the US, few food service workers get paid sick leave so they may show up at work sick because they are concerned about the loss of income and the impact on their jobs.  It’s also important to ensure that workers understand the importance of good hygiene and have access to both water and soap and time to effectively wash their hands.

The final step in the Cause Mapping process is to develop solutions to reduce the risk of the problem recurring.  The solutions to this problem are both simple in concept and difficult to effectively implement.  Ideally, food workers should stay home when they are ill and for at least 48 hours afterwards, but this is much easier said than done for many people.  Food workers should also wash their hands after using the bathroom and before handling any food, but it can be difficult to enforce the policy because employers and managers aren’t (and shouldn’t be) closely monitoring what happens during bathroom breaks.

To view a high level Cause Map of this issue, click on “Download PDF” above.

Norovirus Outbreak on Cruise Ship Sickens Over 600

By Kim Smiley 

A cruise ship has once again made national headlines for a negative reason.  A norovirus outbreak on Royal Caribbean’s Explorer of the Seas sickened nearly 700 hundred people during a cruise that ended on January 29, 2014.  Noroviruses are extremely unpleasant and cause extreme stomach cramps, vomiting and diarrhea, not exactly the stuff fantastic vacation memories are made of.  According to the Centers for Disease Control and Prevention (CDC) there have been 56 gastrointestinal outbreaks on cruise ships in the past five years, but this outbreak is notable because it was one of the largest in 20 years.

This incident can be analyzed by building a Cause Map, a visual format for performing a root cause analysis that intuitively shows the cause-and-effect relationships between the causes that contribute to an issue.  A Cause Map is built by asking “why” questions and documenting the answers. ( To view a high level Cause Map of this example, click on “Download PDF”.)

In this example, the initial source of the norovirus is not known and may not be able to be determined, but a Cause Map can still be helpful in understanding how the outbreak spread and how the outbreak impacts the goals of the company.  The CDC did investigate the outbreak, but it can be difficult to determine how the norovirus was brought onboard.   Noroviruses are common, especially during the January through April peak season for norovirus infections, and cruise ships need to have a plan to deal with sick passengers because simply preventing a norovirus from coming onboard isn’t realistic.

Once a person infected with a norovirus is onboard a cruise ship, the illness can spread quickly because is highly contagious.  Noroviruses can be transmitted by contact with an infected person, consuming contaminated food and even touching contaminated surfaces such as stair handrails.  Cruise ships, along with other confined spaces such as nursing homes, are particularly susceptible to fast spreading outbreaks of norovirus because there is a large number of people in a small space and it can be a challenge to isolate sick people.  Many cruise ships also serve meals buffet style which can pass the virus quickly to a large number of people.

The cruise ship did have a plan in place to help mitigate any outbreaks and the number of ill passengers was decreasing by the time the ship returned to port.  Sick passengers were isolated to their cabins and crew increased cleaning and sanitation of the ship during the cruise.  The ship was also given an especially thorough cleaning and extra sanitizing prior to departure of the next cruise.  In order to track and help cruise ships prevent outbreaks the CDC also runs a Vessel Sanitation Program, which monitors illness at sea and provides information about disease prevention.  If plan to take a cruise, the best way you can protect yourself is by frequently and thoroughly washing your hands with soap and water.

Visit our previous blogs if you are interested in learning more about other cruise ship examples:

Engine Room Fire Results in Cruise Ship Nightmare

Cruise Ship Loses Power

The Salvage Process of Costa Concordia