Food Protection Connection: Food Safety: Cruise Ship Illness

(reprinted from Dietary Manager, February 2003)

Repeated news stories of foodborne illness (FBI) outbreaks on cruise ships throughout the fall of 2002 have brought startled confusion to many people… most of all, to those of us charged with understanding and managing food protection. What exactly is going on, and why do people keep getting sick? Is there anything we need to know to protect our own institutional foodservice customers? Here are some questions and answers to help make sense of the mysterious "cruise ship illnesses."

What’s been happening?

In the first 11 months of 2002, the Centers for Disease Control (CDC) received reports of 21 FBI outbreaks on a total of 17 cruise ships. Most occurred from July through December, and many received high-profile news coverage, such as several Carnival cruises, Holland America cruises, and the Disney Magic cruise. In some cases, ships were taken out of service, disinfected, and then boarded for new cruises, where both crew and passengers again became ill. Some passengers booked for cruises have cancelled their plans.

How many people were affected?

Numbers vary, but some incidences have involved dozens or even hundreds of people. The CDC Vessel Sanitation guidelines require cruise ships to report illness any time more than 2 percent of those present on the ship complain of gastrointestinal symptoms (e.g. vomiting, diarrhea). Then, scientists investigate. In the 2002 cases, anywhere from 2 percent to 41 percent of crew/passengers have been reported ill.

What caused the illnesses?

Answers are not conclusive for each case. However, about half have been confirmed as Norwalk virus. Today's laboratory procedures allow CDC experts to analyze molecules to identify actual strains of the virus and trace them back to sources, or link them to outbreaks in other locations. One source traced (by statistics only) to a meal eaten off-ship. The virus came on-board through people, and then traveled from person-to-person. Remaining cases seem to be all person-to-person, with no food source identified. Three outbreaks were definitely bacterial illnesses, and another nine remain inconclusive.

OK, but is this really a foodservice problem?

The answer is two-fold: Yes, Norwalk virus can travel through food. But no, not all Norwalk virus cases are transmitted through food. Here are more CDC figures from a five-year analysis of Norwalk illnesses: 39 percent passed through food, 12 percent from person-to-person, 3 percent through water, and 18 percent unknown. Like institutions, cruise ships are subject to routine sanitation inspections, and officials report good scores in recent cases.

How does person-to-person transmission occur?

This can be a situation where one person has the virus. That happens easily, as CDC says there are 23 million cases per year in the US. This person may have the virus on hands due to fecal-oral contamination (not washing hands after using the restroom). Then, this person touches someone else, or touches a surface (e.g. a doorknob or railing) that someone else touches. The second person touches his mouth or food and ingests the virus. Scientists explain this is a common problem when people are contained in closed quarters, such as on a cruise ship.

Are there similar situations on land?

Yes. Nursing homes are a great example. So are hospitals, day care centers, and schools…any place where people tend to stay in one place in large groups. In fact, the virus was first identified when school children and teachers became ill in Norwalk, Ohio in 1968. That’s how the virus got its name. The "closed-quarters" situation is compounded when customers are not able to practice good personal hygiene. In day care centers, for example, there may be more fecal-oral contamination than in other settings. Officials also point out that the virus is problematic in nursing homes, if residents have incontinence, reduced mobility, and/or reduced states of alertness – all of which could contribute to poor hygiene and virus transmission.

So, have there been outbreaks on land, too?

Yes, plenty. In 2002, scientists noted a rise on land as well as on sea. In fact, some speculate that this land-based upsurge may explain the rise in cruise-related illnesses. Passengers boarding a cruise ship are more likely to have the virus, prime for transmission. In addition, CDC provides figures on where Norwalk outbreaks originate: 39 percent from restaurants, 29 percent nursing homes and hospitals, 12 percent schools and day care centers, 10 percent vacation settings (including cruise ships), and 9 percent other settings.

What's the course of the illness?

It begins 12-48 hours after exposure, and of course, not everyone exposed actually becomes ill. Illness, characterized by nausea, vomiting, diarrhea, abdominal cramps, and sometimes headache, fever, and muscle ache, lasts 12-60 hours. For most healthy people, there are no serious complications. For a medically compromised individual, the illness can cause severe dehydration or (rarely) become fatal.

Are there antibiotics or treatments?

No, generally, antibiotics don’t work on viruses. There is no known drug to “cure” or prevent a Norwalk illness.

Can a person develop immunity?

Yes, some people develop short-term immunity. Furthermore, scientists suspect some people become "shedders," transmitting the virus for long periods of time, even while experiencing no symptoms of illness.

What are the food-related issues?

For those cases spread through food, common vehicles are shellfish, salads, and deli sandwiches. Food may be contaminated at its production source. For example, oysters grown in contaminated water or raspberries irrigated with contaminated water may contain the virus. In addition, a foodservice worker who has the virus and does not practice thorough, frequent handwashing may pass the virus from hands to a raw food, such as lettuce or cake frosting. The food is not cooked (heated), so the virus survives. Others eat the food and become ill.

OK, let's say I run a cruise ship and we have a Norwalk outbreak. What do I do to control it?

As the news stories suggest, the answers are not as easy as we’d like. CDC officials advise quarantining ill passengers and crew members, and practicing very vigorous, frequent handwashing. Note that passengers need to play a role to protect themselves by washing hands before eating and after using the restroom. When CDC officials find the virus on a ship, they typically suggest disinfection to remove contamination. This is not necessarily very effective, though. One ill person boarding the pristine ship can start the cycle all over again.

How about if I work in an institution?

Institutional managers need to be alert to symptoms of foodborne or gastrointestinal illness and call in local health officials for help when there is a possibility of outbreak. (Remember, that’s just two or more people with the same symptoms, which may ultimately trace to a common source.) Throughout any closed-quarters institution, sanitation and hygiene are critical controls.

How about food service?

As a dietary manager, you can continue to insist on immaculate personal hygiene among your staff. Realize the likelihood that an employee will come to work one day with Norwalk virus is actually pretty high. Handwashing can prevent transmission. More than that, though, you want to enforce policies about employee illness, and prevent employees experiencing diarrhea or vomiting from working with food. As for food itself, you want to cook shellfish to time and temperature standards, and use reliable sources for all food. For any food that does not undergo cooking – such as salad and cold sandwiches – you can enforce very stringent hygiene standards for preparation staff. Keeping public areas that people touch clean and sanitary can help, too.

What about staff and customer education?

As a dietary manager, you may empathize with the dilemmas faced by cruise ship operators. Part of the Norwalk issue lies beyond their direct control due to person-to-person transmission. In an institution, you may experience the same dilemma. In fact, statistics suggest Norwalk-related illness is a much bigger problem in institutions than it is on cruise ships. However, you can help through education. You can encourage staff and customers to recognize that everyone needs to take responsibility, particularly with personal hygiene and illness reporting.

The high-profile cruise ship illnesses rightfully raise concerns among food protection professionals. While we would like to hear clear answers and know we can totally contain the Norwalk virus threat, solutions are not simple. They involve customers as well as foodservice and other staff. They are especially challenging in closed-quarters institutions, such as nursing homes and schools. With cautious management, however, a dietary manager can play a critical role in helping to prevent and contain Norwalk-related illness.

By Sue Grossbauer