How to prevent Norovirus or Norwalk disease in Cruise Ships

by OldSailor on November 6, 2007


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Virus in Cruise ships. What is the relevance? Well. wikipedia lists the following as cases of Noroviruses or Norwalk disease on Cruise Ships so far occurred this year.

  • In January 2007, several cases were discovered aboard the cruise-liner Queen Elizabeth 2 of Cunard Line in what the Center for Disease Control (CDC) called an “unusually large outbreak.” Seventeen percent (276 out of 1,652) of the passengers on board reportedly fell ill. 28 crew members were also ill.
  • On its 1 April 2007 voyage, the Princess Cruises ship Caribbean Princess had at least 79 passenger and 4 crew member cases of norovirus, or Norwalk disease.
  • In late May 2007, nearly 200 passengers and 10 crew members aboard Royal Caribbean’s newest ship, Liberty of the Seas, contracted Norovirus.
  • In late August 2007, in excess of 500 passengers and unknown number of crew members contracted Norovirus aboard the Celebrity Cruises cruise ship Millennium, sailing between Barcelona and Venice (Aug. 17-29, 2007). Outbreak happened before the end of 12-day cruise, mostly older people fell ill, unknown, but considerable number of them were hospitalized in ship’s hospital and after disembarkation around 10 of those patients/passengers were sent home (mostly to the U.S.) on stretchers. Italian ambulances were delivering them to Marco Polo Airport in droves.

1.What is Norovirus or Norwalk disease?

Center for Disease Control (CDC) gives the following facts.

  • Noroviruses (genus Norovirus, family Caliciviridae) are a group of related, single-stranded RNA, nonenveloped viruses that cause acute gastroenteritis in humans. Also described as “Norwalk-like viruses” (NLV),this group of viruses has also been referred to as caliciviruses (because of their virus family name). Noroviruses are named after the original strain “Norwalk virus,” which caused an outbreak of gastroenteritis in a school in Norwalk, Ohio, in 1968.
  • 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 any serious long-term sequelae. Studies with volunteers given stool filtrates have shown that asymptomatic infection may occur in as many as 30% of infections, although the role of asymptomatic infection in norovirus transmission is not well understood.
  • Noroviruses are transmitted primarily through the fecal-oral route, either by consumption of fecally contaminated food or water or by direct person-to-person spread. Environmental and fomite contamination may also act as a source of infection. Good evidence exists for transmission due to aerosolization of vomitus that presumably results in droplets contaminating surfaces or entering the oral mucosa and being swallowed. No evidence suggests that infection occurs through the respiratory system.
  • Noroviruses are highly contagious and as few as 10 viral particles may be sufficient to infect an individual. During outbreaks of norovirus gastroenteritis, several modes of transmission have been documented; for example, initial foodborne transmission in a restaurant, followed by secondary person-to-person transmission to household contacts. Although presymptomatic viral shedding may occur, shedding usually begins with onset of symptoms and may continue for 2 weeks after recovery. It is unclear to what extent viral shedding over 72 hours after recovery signifies continued infectivity.
  • 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. Recent evidence also suggests that susceptibility to infection may be genetically determined, with people of blood group O being at greatest risk for severe infection.
  • Most foodborne outbreaks of norovirus illness are likely to arise though direct contamination of food by a food handler immediately before its consumption. Outbreaks have frequently been associated with consumption of cold foods, including various salads, sandwiches, and bakery products. Liquid items (e.g., salad dressing or cake icing) that allow virus to mix evenly are often implicated as a cause of outbreaks. Food can also be contaminated at its source, and oysters from contaminated waters have been associated with widespread outbreaks of gastroenteritis. Other foods, including raspberries and salads, have been contaminated before widespread distribution and subsequently caused extensive outbreaks.
  • Waterborne outbreaks of norovirus disease in community settings have often been caused by sewage contamination in water.

2.How to battle Noroviruses on Cruise Ships?

An interesting article in webmd throws some light on this.

  • In the semi-confined quarters of a cruise ship, contagious illnesses can spread fast, particularly noroviruses. These viruses cause what many call the “stomach flu.” Typical symptoms of nausea, vomiting, diarrhea, and stomach cramping last for one to two days.
  • Noroviruses flourish in the winter, but also year round.
  • Since 2001, more outbreaks of gastrointestinal illness have been reported. The reasons? More passengers, more ships and an average cruise length of seven days — ample time for people to mingle and come in contact with infectious germs. However, the risk of gastrointestinal illness is still small: less than 1% during an average week-long cruise.
  • Passengers can fall ill if they touch objects or surfaces contaminated with norovirus (doorknobs, railings, elevator buttons, or counters) and then place their hand in their mouth.
  • People can also be infected if they have direct contact with a sick person or consume food or drink that is contaminated with norovirus.
  • If an ill person vomits or has diarrhea in a whirlpool bath or swimming pool, others who come in contact with the water can be infected, too.
  • Some tips to reduce the risk of gastrointestinal illness on a cruise ship:
    • Wash your hands for at least 20 seconds before eating or smoking. Also wash hands after using the restroom, returning to your cabin, changing a diaper, helping a sick person, or touching surfaces that a lot of other passengers have touched, such as doorknobs and railings.
    • After you’ve washed your hands in a restroom, dry your hands with a paper towel and use the towel to turn off the faucet and open the door.
    • Washing with warm water and soap is best, but if you can’t do so during an excursion, use an alcohol-based gel hand sanitizer that contains 62% ethanol.
    • Notify cruise staff about sick passengers.

OldSailor remembers the old saying “Prevention is better than cure”.

Update: June 07, 2008

Norovirus attacks cruise ship Ventura. 20 passengers affected. Read more from Telegraph.

Update: July 07, 2009

Two hundred passengers of Marco Polo cruise liner are showing symptoms of Noro Virus, off the coast of Scotland. Read more from Guardian.

View a video clip from ITN News: Ship passengers in hospital following vomiting bug scare

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