What and why about norovirus

March 1, 2007
What do cruise ships and restaurants have in common? Both have recently experienced widely publicized outbreaks of norovirus infections among their passengers and patrons.

by Mary Govoni, CDA, RDH, MBA

What do cruise ships and restaurants have in common? Both have recently experienced widely publicized outbreaks of norovirus infections among their passengers and patrons. In 2006, there were approximately 35 separate outbreaks of gastrointestinal illness among cruise passengers on various cruise lines. Of these, 28 were determined to be caused by the norovirus. In the remainder of the cases, either the causative microorganism was not yet confirmed or not linked to norovirus. These outbreaks affected hundreds of passengers.

In a number of other instances, several of them in my home state of Michigan, norovirus was determined to be the cause of massive outbreaks of gastrointestinal illness among people who ate at certain restaurants. One particular outbreak was reported to have affected more than 500 individuals who ate at one restaurant. The local health department reported that at least one individual who was preparing food at the restaurant had symptoms of gastrointestinal illness.

Should you be afraid to go on a cruise or eat in a restaurant? Not necessarily, but having a basic knowledge of noroviruses and how they are spread may help you better understand how and why these types of outbreaks take place - and what you can do to prevent them.

What is a norovirus?

Norovirus is a term used to describe a group of viruses called calciviruses, formerly referred to as a “Norwalk-like” virus, which attacks the stomach and intestines and causes gastroenteritis, or what some would describe as “stomach flu.” Symptoms include vomiting, diarrhea, and stomach cramps, which have an acute or sudden onset. Along with the acute symptoms, fever, chills, muscle aches, and headaches may also occur. Although these illnesses are rarely fatal, death can occur from the severe dehydration that may result from vomiting and diarrhea. The virus is said to have an incubation period of 12 to 48 hours, and symptoms typically last 12 to 60 hours.

How is a norovirus transmitted?

The Centers for Disease Control and Prevention states that the most likely primary route of transmission of norovirus is fecal-oral. This means eating food or drinking liquids that have been contaminated with norovirus. Touching surfaces contaminated with norovirus and then placing hands in the mouth can also cause transmission. Individuals can become ill when caring for infected individuals and/or sharing eating utensils with someone who is infected. The CDC also states that individuals who have become ill with gastroenteritis due to norovirus infection can remain infectious for seven days or more after symptoms subside. It was previously believed that a person remained contagious for only 48 to 72 hours after symptoms subsided, but recent tests suggest that it may be much longer. This may explain the number of outbreaks that have been linked to restaurants where employees were said to have returned to work shortly after their symptoms subsided.

Why cruise ships? This may be due to the fact that many cruise ships dock in countries where sanitation levels are inadequate, resulting in contaminated food and/or water. Passengers sailing on cruise ships, as well as the workers on the ships, live in relatively close proximity to each other, making disease transmission more likely. Outbreaks on cruise ships are widely publicized partly because they make good news stories, but primarily because sanitation on cruise ships is closely monitored by health department officials and outbreaks must be reported.

Prevention methods

There are many methods of preventing norovirus infections which include recommendations for food handlers, preparation of foods, caring for sick individuals, and general safety guidelines.

Food handlers should not work in food preparation until they have had no symptoms for at least two to three days. Thorough hand washing and protective gloves are also recommended. In addition, food handlers should be assigned tasks that do not involve food preparation for several days after recovering from their illness, such as cashiering or hostessing.

When caring for an individual with gastroenteritis, it is important to note that their vomit is infectious. Thorough cleaning and disinfection of areas contaminated with vomit is very important. Also, cleaning or disposing of items that have been in contact with contaminated food is critical. Cleaning the bed or linens that may have been soiled by vomit and/or diarrhea in hot water is another important tool for preventing the spread of these types of infections. Washing raw fruits and vegetables is always recommended. And last, but certainly not least, thorough hand washing is always an important infection-control tool. Soap and water and waterless alcohol hand sanitizers are cited by the CDC and other sources as effective in preventing the spread of these and other microorganisms.

For more information about norovirus and related outbreaks, go to www.cdc.gov. You can research the sanitation records of individual cruise lines, gather additional information on diagnosis and prevention of norovirus infections, and much more.

Mary Govoni, CDA, RDH, MBA, is the owner of Clinical Dynamics, a consulting company based in Michigan. She is a member of the Organization for Safety and Asepsis Procedures and is a featured speaker on the ADA Seminar Series. She also writes a column for Dental Office magazine. She can be contacted at [email protected].