There’s no doubt about it:  an outbreak of gastrointestinal illness is the fastest way to ruin a cruise ship vacation.

A recent study, published in the Nov. 1 issue of Clinical Infectious Diseases suggests improperly cleaned ship restrooms as a possible cause of these outbreaks. 

According to researchers, the Centers for Disease Control and Prevention (CDC) identified contamination with norovirus as the problem in almost all of these infections. Norovirus can survive for weeks on surfaces at room temperature, and it is difficult to kill. According to Dr. Philip C. Carling, the lead author of the study and professor of clinical medicine at Boston University, “It isn’t killed by alcohol hand rubs. Chlorine bleach is the only thing that works.”

Carling’s team tested toilets on 56 cruise ships, using an easily removable solution visible only under ultraviolet light. Then they monitored them for five to seven days to see if the solution had been removed by cleaning or disinfecting.  Four of the vessels had perfect or near-perfect scores: the restrooms were thoroughly cleaned nearly every day. But overall, only 37 percent of 8,344 objects were cleaned daily.

Although the survey was not designed to establish the cause of any illness, the restroom cleanliness scores were slightly lower on ships that had outbreaks than on those that had none.  The difference was not statistically significant, but the authors said the findings were consistent with the possibility that restroom contamination contributed to norovirus epidemics.

The study’s authors write that their findings suggest the CDC’s inspection criteria “have a low sensitivity for identifying shortcomings in actual public-restroom environmental hygiene practice.” A similar study of acute-care hospitals published last year found that only 46.5 percent of objects in toilet areas were consistently cleaned.

For more information on surface disinfection to prevent norovirus and kill other micoorganisms that can cause illness, please visit the CDC.

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