A flock of seagulls?
A flock of seagulls?

One thing that cruise ships are known for is their food. Studies suggest that passengers put on half a kilo in weight a day over the course of a 14 day cruise*. Twenty-four hour buffets mean that you can get whatever your heart desires, from pizza to freshly shucked oysters, at 2am. Outbreaks of infectious diarrhoea and vomiting are common in the cruise industry but no more common than in nursing homes or schools. The only real difference is that there is no escape. People often think that cruise ships are rife with disease though the fact is that their kitchens are probably cleaner than your local fast food joint. Random inspections by either the CDC, AQIS or the UK Port Authority can occur any time the ship is in port and so the onus is on the shipboard company to keep the food service areas clean.

So where do the outbreaks come from? Passengers. On embarkation day every passenger has to fill in a health questionnaire regarding the presence, or absence, of symptoms suggestive of vomiting or diarrhea. Unfortunately passengers commonly lie if they think you might deny them boarding. Once they have set sail the infected are free to wander around touching things – lift handles, slot machine arms, poker chips – and spreading their dirty love to their fellow travelers. Your only chance to stop the plague then is to rely on the honest passengers, confine them to their quarters and hope you have countered the spread. Norovirus, however, is highly contagious. It even had a strain named after a cruise ship, though this has since been changed after lobbying from Princess. If one patient with Noro vomits in a crowded lift 50% of those struck will be vomiting before sundown. All cases of gastroenteritis that present to the medical centre have to be reported to the local authorities and once a threshold level is reached an outbreak is declared.

200 cases of gastro require 200 cabin visits and 200 follow up phone calls and contact tracings to be done as well as food diaries for all. Just like most apocalyptic zombie horror movies the contagion can often be traced back to one or two individuals or shoreside restaurant.

So other than looking after the individual patient the ships doctor has to also consider the public health of the passengers. We would regularly monitor the levels of gastroenteritis and influenza-like illness on board. All patients with pneumonia would get urine Legionella antigen testing and rapid influenza tests (though not accurate) were used to limit spread of the disease. Each ‘flu season the medical team had to coordinate the on board vaccination program. At the time of SARS and avian influenza we would even have to use thermal imaging cameras to check the body temperature of every passenger before they were allowed ashore.

In my time onboard I have had to deal with a number of public health menaces  from TB, influenza, legionella and malaria to the more mundane gastroenteritis. None were more problematic onboard than gonorrhoea. But that is a tale for another time…

*not an actual study

Dr. Andrew Tagg left the shipboard life in 2009 to settle down and lose weight.  He is currently an advanced trainee in EM working in Melbourne’s western suburbs.  He still has the uniform. Contact him via Twitter @andrewjtagg

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