Archive Number 20100223.0607
Published Date 23-FEB-2010
Subject PRO/EDR> Gastroenteritis, cruise ship - Caribbean: norovirus susp

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A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases

Date: Mon 22 Feb 2010
Source: USA Today, Cruise Log [edited]

Celebrity Cruises ship in Caribbean hit by major outbreak of stomach illness
A Celebrity Cruises ship sailing in the Caribbean is experiencing an
unusually large breakout of a norovirus-like illness, with more than 15 per
cent of passengers having fallen ill. Spokeswoman Cynthia Martinez told USA
Today that about 300 out of 1800 passengers on the Celebrity Mercury are
suffering from stomach upset, vomiting, and diarrhea. The ship set sail out
of Charleston on 15 Feb 2010 on an 11-night voyage to the Caribbean that is
scheduled to end in the city on Fri 26 Feb 2010.

Martinez told the Associated Press that the ship's medical facilities have
been overwhelmed, and the vessel brought on an extra doctor and nurse
during its latest port call. Martinez told USA Today that samples from
infected passengers would be dropped off on Tuesday [23 Feb 2010] at a
laboratory for testing to determine the exact cause of the illness. The
outbreak isn't expected to have an impact on next week's [week of 1 Mar
2010] cruise on the ship, she said. "We have already begun extra cleaning,
in an abundance of caution," Martinez said. "We do not expect a delay at

Such outbreaks are becoming increasingly rare. The number of outbreaks of
gastrointestinal illness on cruise ships sailing from US ports has been
dropping sharply in recent years and is at its lowest level in nearly a
decade. The Centers for Disease Control and Prevention (CDC) in Atlanta
recorded just 13 outbreaks of illnesses such as norovirus [infection] on
cruise ships operating out of US ports in 2009, down from 15 in 2008, 21 in
2007, and 34 in 2006.

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[A norovirus is assumed on basis of symptoms and duration of illness to be
the etiologic agent in this outbreak of gastroenteritis. Cruise ships
arriving in US ports must report all cases of gastrointestinal illness
treated by on-board medical staff to CDC's Vessel Sanitation Program
division, and a separate notification is required when the number of cases
exceeds 2 per cent of passengers and crew. When the number of cases exceeds
3 per cent of passengers and crew CDC issues a public report.

According to the Cruise Log of USA Today an analysis of the public reports
for 2009 shows that, as in past years, the majority of the outbreaks -- 7
out of 13 -- were due to norovirus infection. There also was one outbreak
caused by _Cyclospora cayetanensis_, on Holland America's Amsterdam cruise
ship in April of 2009, and one outbreak that was the result of both
_Shigella sonnei_ and _Escherichia coli_ (on Princess Cruises' Island
Princess ship also in April 2009). CDC lists the cause of 4 of the 13
outbreaks in 2009 as unknown or pending. Of the 13 outbreaks, 6 were on
ships operated by Holland America -- a line that has had a disproportionate
share of the industry's gastrointestinal illness outbreaks for several
years. Only 2 other lines had more than one outbreak: Princess Cruises (3)
and Celebrity Cruises (2). Two other lines -- Norwegian Cruise Line (NCL)
and Carnival -- each had a single outbreak.

Holland America has led the industry in gastrointestinal illness outbreaks
reported to the CDC for 4 straight years with 6 in 2008, 5 in 2007 (tying
with NCL), and 7 in 2006, according to CDC data. Notably, a number of major
lines in 2009 -- including Royal Caribbean, Disney, and Cunard -- did not
report a single outbreak to CDC. The number of outbreaks recorded by CDC in
2009 was lower than in any year since 2001, when there were just 4 outbreaks.

Sometimes called the "24-hour flu", norovirus is the commonest cause of
stomach illness in the United States and elsewhere in the northern
hemisphere, accounting for around half of all cases, according to CDC. It
breaks out regularly in schools, nursing homes, hospitals, offices, and
other places where people congregate.

Noroviruses (genus _Norovirus_, family _Caliciviridae_) are a group of
related, single-stranded RNA, non-enveloped viruses that cause acute
gastroenteritis in humans. This group of viruses has also been referred to
as caliciviruses (because of their virus family name) and as small round
structured viruses, or SRSVs (because of their morphologic features).
Noroviruses are named after the original strain "Norwalk virus", which
caused an outbreak of gastroenteritis in a school in Norwalk, Ohio, in
1968. Currently, there are at least 5 norovirus genogroups (GI, GII, GIII,
GIV, and GV), which in turn are divided into at least 31 genetic clusters.

The incubation period for norovirus-associated gastroenteritis in humans is
usually between 24 and 48 hours (median in outbreaks 33 to 36 hours), but
cases can occur within 12 hours of exposure. Norovirus infection usually
presents as acute-onset vomiting, watery non-bloody diarrhea with abdominal
cramps, and nausea. Low-grade fever also occasionally occurs, and vomiting
is more common in children. Dehydration is the most common complication,
especially among the young and elderly, and may require medical attention.
Symptoms usually last 24 to 60 hours. Recovery is usually complete and
there is no evidence of serious long-term sequelae. Mechanisms of immunity
to norovirus are unclear. It appears that immunity may be strain-specific
and lasts only a few months; therefore, given the genetic variability of
noroviruses, individuals are likely to be repeatedly infected throughout
their lifetimes. This may explain the high attack rates in all ages
reported in outbreaks. Further information can be obtained at
<>. - Mod.CP

Maps of the Caribbean Islands are available at
<> and
<>. - Sr.Tech.Ed.MJ]