Noroviruses - A Cruise Ship Owner's Nightmare

Dr Tim Wreghitt explains how noroviruses spread themselves through projectile vomit and use cruise ships as the perfect culture vessel.
13 May 2007

Interview with 

Dr Tim Wreghitt, Addenbrookes Hospital


Noroviruses have been receiving media attention recently after causing a major outbreak of illness on amongst passengers and crew alike on the Queen Elisabeth II cruise ship in January. Dr Tim Wreghitt, consultant virologist at Addenbrookes Hospital in Cambridge, came to the studio to let us know the extent of the problem.NorovirusChris -   As a Consultant Virologist, norovirus must be a major problem for you.Tim -   It certainly is.  Every year we see major outbreaks of diarrhoea and vomiting throughout England, some years we have more, some less.  That's largely to do with whether or not 'there's a new strain going around' as they say.Chris -   So what actually is norovirus, and why is it such a problem?Tim -   Well norovirus is a small RNA virus which originated, or was first discovered in a town called Norwalk in Washington state.Chris - So nothing to do with Norway?Tim -   No, and nothing to do with "Nor-a-lorravirus", Cilla Black is completely blameless.  The virus was known as Norwalk virus originally, and is now known as Norovirus officially.  It's really very common in the community.Chris -   So how does it actually spread from one person to the next? Does it come to us from animals? What sort of problems does it cause?Tim -   The biggest problem with Norovirus is it causes projectile vomiting.  I shouldn't have to say more about that, many of you have probably experienced it too, I know I certainly have. You have no warning that you're going to be sick at all;  Someone goes "Bleugh" and they're sick, they didn't know they were going to do it and wherever they are, be it a hospital ward, a school, a cruise ship, that's it.  That means their whole environment around them, for about 10-20 feet, is contaminated and all you can do then is to try and cope with that contamination.Chris -   Is it just on surfaces, or is the air littered with these tiny viral particles so anyone standing in that blast zone could breathe it in.Tim -   Yes, the air is contaminated with 'bounce-backs' and particles, but the most important problem is that it gets into carpets and curtains and all that kind of thing.  This is one of the reasons why we don't like a lot of carpets and curtains in hospitals, they're very difficult to decontaminate as you literally have to take them all down, clean them and then put them back.Chris -   How long does the virus stay in the environment?Tim -   In the air, for very short periods of time.  It settles down into the carpet and onto the walls, but then once it's settled it will stay there for a long time, which is why you simply have to remove it.Chris -   So that's the only way to clean it up?Tim -   Yes.Chris -   So could you just talk us through what would be the scenario;  You're running a cruise, lots of people join your boat at Portsmouth, very excited about their holiday... What would happen next?Tim -   The interesting thing about cruises is that they're ideal culture vessels for viruses, because you have a new lot of humans coming in every week or 2 weeks and one group gets it, contaminates the area, so the next group gets it...  It's fantastic for viruses.Chris -   So what's the time scale?  Are you going to see people beginning to get sick 2 days after you set sail?Tim -   First of all, you need someone who's incubating the infection, they will come on board and be sick in a public area.  "Bleugh!"  And then whoever is in that area will be contaminated.  Not only do you have the original area of the ship that 's contaminated, which will stay an area where people can pick up infection for many days, but then a day or so later those exposed people will contaminate other areas.  It's just amplifying the whole time.Chris -   So why aren't we all having this all the time? If it's as infectious as that, as easy to catch as that and as nasty as that, why aren't we all continuously having this?Tim -   Well, you know Chris a lot of people listening will have probably had this in the last year or two.  I've had it just last December, and knowingly twice in my life.  I think if you talk to people they will know of a hospital ward or a school outbreak...  I think there is quite a bit there in the community, in households as well as in hospitals.  One thing I do want to say, is despite criticism of hospitals, it's very difficult once it gets into a ward.  The only thing you can do is batten down the hatches, restrict access and try and remove symptomatic patients from asymptomatic patients, and then clean very carefully afterwards.This is happening in households throughout the country all the time.Chris -   So if I brought this home, would my family automatically catch it? What could I do to make sure the rest of my family didn't catch it?Tim -   Well it's the old adage of hand washing, largely.  A lot of infections are spread by hands.  All you can do if you are having diarrhoea and vomiting is to try and use, if you have the luxury, a second toilet, or be very careful how you clean the toilet, particularly the lavatory seat.  Generally try to decontaminate the environment and keep other family members away from you if you can.  It's easier said than done, and usually it's not possible.  Even if you're very careful, you'll often find that a whole family will go down with this thing.Chris -   And once you've had it, are you then immune, or are there lots of different types?  Does it change so other people can catch it?Tim -   There are a few problems here; once you've had it, you're only immune for a few months.  Equally the virus, like the influenza virus, is very clever; the RNA mutates so that every year or two a brand new virus will emerge that no one is immune to.  This virus has got it sussed.  It will make sure that it's got a life span forever; mutating slightly, infecting a new group of people...  It's like influenza, it's very difficult to get rid of unless you have a vaccine and we don't have a vaccine against norovirus.


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