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Illness on cruise ship in Caribbean - norovirus suspected

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  • Illness on cruise ship in Caribbean - norovirus suspected,81484

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

    ************************************************** ***********
    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.

    communicated by:
    HealthMap Alerts via ProMED-mail

    [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]