Suspected Norwalk Virus Outbreaks in Cruise Ships in the Caribbean

There have been new reports over the last few weeks of outbreaks of Norwalk Virus infection among passengers and staff of various cruise and cargo ships in the Caribbean.  The CDC’s Vessel Sanitation Program (VSP), which conducts surveillance for acute gastroenteritis on cruise ships with foreign itineraries sailing into U.S. ports, received reports of 21 outbreaks on 17 cruise ships during the period Jan 1^st – Dec 2^nd, 2002.  Nine were confirmed by laboratory analysis of stool specimens to be associated with noroviruses (i.e., Norwalk-like viruses or NLV).    Three of the outbreaks of Norwalk-like virus infection were in vessels in the Caribbean during the period September 28^th to November 16^th.

CAREC has been in touch with the Centers for Disease Control and Prevention (CDC) Vessel Sanitation Program about the situation with the cruise ships and suspected Norwalk Virus outbreaks.   More information is available in the December 13^th, 2002 edition of the Morbidity and Mortality Weekly Review at:   http://www.cdc.gov/mmwr

·        Norwalk-like Virus infection is an intestinal illness caused by consuming contaminated food or water. Common symptoms include nausea, vomiting, diarrhoea and abdominal pain. Headache and low-grade fever may also occur.  Infected people usually recover in 2 – 3 days without serious or long-term health effects.

·        Norwalk-like Virus infection is not considered a Quarantinable illness.  That is, it is not necessary to confine all ship-board persons to their quarters nor to prevent ships from docking at port.

·        The virus is transmitted by hands contaminated through the faecal-oral route, directly from person to person, through contaminated food or water, or by contact with contaminated surfaces or formites (small bits of infected material).

·        Transmission by aerosol from virus particles released by the act of vomiting has been postulated but it is more likely that formites may contaminate the clothes of persons in the immediate vicinity of someone vomiting and cause infection.

·        A very low infective dose (<10 virus particles) can cause infection and persistence in the environment,  contaminated surfaces or objects may act as a vehicle for infection and making transmission difficult to control through routine sanitary measures.   Such conditions occur in ships where there are a high number of persons in a relatively confined space.

·        Norwalk-like Virus is not considered a risk to a general population in an open environment. 

Meanwhile, the following recommendations are suggested:-

§         Any persons who present symptoms and signs like nausea, vomiting, diarrhoea, and abdominal pain should be reported to the Epidemiology Unit, Ministry of Health.

§         Personnel who may have to handle luggage or passports or documents from cruise ships are advised to wear disposable gloves and to pay scrupulous attention to hand washing before eating or drinking.

§         Health personnel who may attend to suspected persons should wear barrier clothing and should inspect clothes for evidence of formites from vomitus.

§         In addition to emphasizing basic food and water sanitation measures, control efforts should include thorough and prompt disinfection of ships during cruises, and isolation of ill crew members and, if possible, passengers for 72 hours after clinical recovery.

Dr. Robert Lee

Manager (Ag), Epidemiology Division