According to an article in San-Diego's Union Tribune, the Holland American ship Ryndam left San Diego for a 10-day Mexican cruise on February 15th, with 1,226 apparently-healthy passengers and 556 crew members on board. By the time the ship returned to port yesterday, 104 of the passengers and 6 crew members had fallen ill with what is suspected to be Norovirus. One of the stricken passengers, an 81 year-old woman, was taken away by ambulance upon disembarking.
Norovirus is a highly infectious – though short-lived – disease, which is easily spread by hand-to-mouth contact. Victims usually suffer from nausea, vomiting and diarrhea. Symptoms, which can begin abruptly and with very little warning, typically last for 24-48 hours. The virus may continue to be shed by victims in their stools for as long as two weeks after they have apparently recovered.
According to the CDC, the Ryndam is the sixth ship to be hit with an outbreak of gastroenteritis so far this year. Norovirus has already been confirmed as the cause of four of the six oubreaks. In 2007, there were 23 gastroenteritis outbreaks on board ships calling at US ports. Sixteen were caused by Norovirus, including outbreaks during three consecutive sailings of the Ryndam last winter.
Cruise ships that call at U.S. ports are subject to inspection under the CDC Vessel Sanitation Program. The inspection scores and detailed reports are all available on the CDC web site, and it's wise to check this site when contemplating a cruise. The Ryndam was last inspected on December 13, 2007 and received a grade of 97 out of 100 (86 or higher is considered a "pass"). But a successful inspection cannot shield a ship from an embarking passenger who is carrying the virus.
Norovirus particles can survive on dry surfaces, such as deck rails, bathroom counter tops and eating utensils for days and – as I mentioned in my recent post about institutional Norovirus outbreaks – are resistant to many common disinfectants. Moist heat and chlorine bleach are the two most effective ways to kill the virus.
Cruise ship passengers are a captive audience – perfect targets for a virus such as Norovirus. The only protection against becoming infected with this virus during an outbreak at sea is to practice scrupulous personal hygiene. Frequent and thorough hand-washing is a must – before every meal, and after touching door handles, rails, elevator buttons, and other surfaces that might have been contaminated by an infected passenger.
For more information on cruising with Norovirus, check out the CDC's Norovirus web page.