"On the last night/morning, many people were stricken with a gastrointestinal illness that caused diarrhea and vomiting. A great deal of vomit was on the stairs, elevator and other public areas by Friday morning." So a passenger from Canada, on December 30, 2005, sailing on the Zuiderdam in the Holland America Line, reported to the website cruisejunkie.com.

Norovirus is a highly contagious gastrointestinal virus where the potential for someone who is sick to infect others exists from the moment they become sick, to at least 3 days after they get better. Disturbingly, some people remain contagious for up to 2 weeks after recovering. This may be a factor in successive cruises becoming infected. And it remains questionable whether sick passengers and crew are confined to their cabins for 3 days after they get better.

Whilst norovirus outbreaks are by no means confined to cruise ships, the nature of a cruise increases the likelihood of an infection spreading. This is similar to the potential for infections spreading in other closed communities like nursing homes. The 'cruise ship virus' can be spread through contaminated food and drink, which is particularly concerning if the crew members who serve or prepare food become sick.

Passengers can pick up the virus from touching infected surfaces like handrails, walls and mirrors. When a suspected norovirus outbreak occurs on a cruise ship, crew will spray disinfectant on all common surfaces, and sick passengers are confined to their staterooms.

Sick passengers and crew have acute symptoms of nausea, vomiting and diarrhea. Some also have stomach cramps, headaches, a low grade fever, and chills. One 21 year old man actually died two days after disembarking from his ship. The cause of death was cited as being complications from a norovirus infection.

This isn't common however. Norovirus infections are usually not significant health risks, though they are highly unpleasant, both for passengers and cruise ship companies. For passengers, what is meant to be a relaxing holiday turns into a retching and wretched nightmare at sea. For cruise companies with ever increasing ship capacities, it is a public relations nightmare.