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Number, severity of acute gastroenteritis outbreaks on cruise ships declining
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The frequency of acute gastroenteritis decreased among cruise ship passengers from 2008 to 2014, and only a small percentage of reported cases were part of a norovirus outbreak, according to a new report from the CDC.
“The number and severity of cruise ship outbreaks of acute gastroenteritis varied during the study period, but were lower than rates reported during 2001 [to] 2004,” the authors wrote.
CDC investigators evaluated data from Vessel Sanitation Program reports submitted by 29,107 cruise ship voyages in the U.S. jurisdiction from 2008 to 2014 to ascertain recent rates of acute gastroenteritis, and also assessed laboratory data to identify the causes of outbreaks.
Acute gastroenteritis (outbreak and non-outbreak cases combined) was reported in 0.18% of 73,599,005 passengers and in 0.15% of 28,281,361 crew members. Only 14.9% of passenger cases and 4.6% of crew cases were part of an outbreak, of which 70.4% and 67.7%, respectively, were caused by norovirus.
The rates of acute gastroenteritis among passengers decreased from 27.2 cases per 100,000 travel days in 2008 to 22.3 cases per 100,000 travel days in 2014, while rates among crew stayed about the same (21.3 vs. 21.6 cases, respectively).
“The rate of illness demonstrated a decreasing but not statistically significant trend for either passengers … or crew members,” the authors wrote. The rate did spike significantly in 2012 for passengers and crew, however, which was “likely related to the emergence of a novel strain of norovirus, GII.4 Sydney.”
Overall, 133 outbreaks were reported and 71% of them had specimens available for testing.
Available specimens showed 97% of outbreaks were caused by norovirus, and 73.8% of the genotyped norovirus specimens were GII.4 strains.
Outbreaks ranged from 15 per year in 2011 and 2014 to 27 per year in 2012 (3-6.5 per 1,000 voyages) among passengers, and from one in 2008, 2011, 2012 and 2013 to four in 2009 and 2014 (0-0.8 per 1,000 voyages). “These differences exhibited a decreasing, although not statistically significant, linear trend,” the authors wrote.
“Fewer and less severe outbreaks are likely the result of earlier detection of acute gastroenteritis, along with cruise industry efforts to identify and control outbreaks by developing and implementing required Outbreak Prevention and Response Plans, using processes and chemical disinfectant known to be effective against a norovirus surrogate and proactively seeking strategies to limit acute gastroenteritis spread,” the authors wrote. – by Adam Leitenberger
Disclosures: Infectious Disease News was unable to confirm relevant financial disclosures at the time of publication.
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