Cruise ship passengers face a growing risk of getting sick to their stomachs, new study findings show.
The expected incidence of diarrheal diseases per seven-day cruise has increased from two cases between 1990 and 2000 to three cases in between 2001 and 2004, the report indicates.
"Despite good environmental health practices on cruise ships, and high performance scores on environmental health inspections, gastroenteritis likely associated with person-to-person spread of illness caused by noroviruses is difficult to predict and prevent," study author Dr. Elaine H. Cramer of the U.S. Centers for Disease Control and Prevention told Reuters Health.
What's more, added the Vancouver, British Columbia-based researcher, the findings can be generalized to airplanes and trains where there's a high density of travelers.
In 2000, the incidence of diarrheal disease among cruise ship passengers was 16 cases per 100,000 passengers, down from 29 cases per 100,000 passengers in 1990. Just a short while later, however, diarrheal disease outbreaks on cruise ships increased. According to the CDC, 29 outbreaks occurred in 2002, compared with just 3 in the previous year.
Cramer and her colleagues, members of the CDC's Vessel Sanitation Program Environmental Health Inspection Team, evaluated the incidence of gastroenteritis on cruise ships that docked in U.S. ports and carried at least 13 passengers from 2001 through 2004. They also explored whether the ships' performance on health inspections was associated with the frequency of outbreaks.
The number of gastroenteritis outbreaks per 1,000 cruises increased from 0.65 to 5.46, they report in this month's issue of the American Journal of Preventive Medicine. What's more, the total number of gastroenteritis outbreaks increased to a median of 15 per year from 2002 to 2004, up from 2 in 2001.
Yet, the ships continued to perform well on regular, unannounced health inspections throughout the study period, with half of the vessels scoring above 95 on a scale of 1 to 100, study findings indicate.
Inspection scores were not associated with either increased or decreased rates of gastroenteritis and they also did not appear to predict more or less frequent outbreaks of the illness, the researchers note.
"The increase we have seen at sea is paralleled by an increase in the prevalence of norovirus-associated gastroenteritis on land," Cramer said. The illness is common in Scandinavia, the UK, Europe and North America.
Norovirus is a frequent cause of gastroenteritis and its symptoms -- including diarrhea and vomiting -- are unpleasant but rarely dangerous. The virus is transmitted through person-to-person contact, contaminated food or water, or by touching a contaminated surface, such as elevator buttons and stair handrails.
However, prospective cruisers need not abandon their plans. Cruisers have less than a 1 percent chance of contracting gastroenteritis while spending an average seven days at sea, the researchers note.
"The most important preventive strategy against gastroenteritis associated with person-to-person transmission of disease is hand washing," Cramer told Reuters Health. "Travelers should wash their hands for 20 seconds frequently, using soapy water and using hand sanitizers only as an adjunct to handwashing, not as a substitute for handwashing," she added.