houstonmd

ehfl is correct -- hydrogen peroxide must be stored in an opaque container because light causes it to break down. When you buy it in the pharmacy, it's usually in a brown plastic bottle, usually about 3%. The Clorox product, both spray and wipes (intended for hospital and clinic use) is 1.4%. It is completely safe for putting on skin and environmental surfaces.

I've just been talking about norovirus here. There are thousands of other organisms to be vigilant about, it's just that norovirus has been shown to be a particular problem on cruise ships. This is because of several factors: a very small number of virus particles is sufficient to cause disease; it persists on environmental surfaces for a long time; the usual cleansers (alcohol, quaternary ammonium compounds) don't touch it; and it can be transmitted after being aerosolized.

The posters are correct about norovirus being a problem in lots of settings. A paper in the Feb 2012 issue of American Journal of Infection Control (http://www.ajicjournal.org/article/S0196-6553(11)01210-7/abstract) found that norovirus was the leading cause of hospital-acquired infections (18%) and was most common in behavioral health and rehab units. There is some similarity between that type of unit and cruise ships -- the patients (passengers) stay for a long time, they interact with each other, they wear their own clothing, they eat together, they are not critically ill (so they don't require the attention of nurses), and they take care of their own hygiene.

The posters are, of course, correct that the problem is the passengers, not the ship, because the ship is an inanimate object that does not suffer from diarrhea. However, the ship is the vector of the spread of the virus because it is the repository of virus. The mosquito is not the cause of malaria, it is the vector which passes the malaria organism from one person to another. That is why public health officials eliminate malaria by eliminating mosquitos. We don't want to eliminate cruise ships, so we have to get better at preventing transmission of the virus from humans to environmental surfaces, and back to other humans.

Some posters noted that they have been on many cruises without getting ill. Let's be grateful for that. Neither my wife nor I have gotten ill on a ship, either. That is what we in medical research call (joking), "an n of one," meaning, the experience of just one case or one individual. Norovirus is the sort of problem where lots of data are needed. The vast majority of folks who got sick on that ship recently had never been sick before, either. In 2013, cruise ships out of the US carried 21 million passengers, and there were 1,238 reported cases of norovirus (http://www.cruising.org/regulatory/issues-facts/public-health-medical-capabilities/norovirus), so you have about one chance in 20,000 of contracting it -- pretty small --but those 1238 people all wished they had been more careful. (Of course, that doesn't count the people who were sick but didn't report it, those who had mild cases, those who were sick but not tested, and those who didn't get sick until after they had disembarked. The actual number of cases is a good deal higher.)

Don't let the fear of getting ill prevent you from taking a cruise or enjoying everything on the ship--just take a few precautions, and you will reduce the chances of getting sick.

Prevention of Norovirus Infection

We recently sailed on the Caribbean Princess out of Houston to the western Caribbean, and I thought I would contribute a few specific comments on health and wellness, which is my professional field.

A lot of people are (justifiably) worried about norovirus. It is a nasty virus (also known as Norwalk virus) that causes nausea, vomiting, diarrhea, and fever, general fatigue and listlessness. Just a small number of virus particles are required for transmission—certainly less than 20, and perhaps as few as five. Infected people are most likely to transmit the virus when then are sick, but they can transmit it just before they fall ill and for several weeks afterward. As with other viruses, it is spread from one person who is infected to another, by ingesting the virus. This can be directly, from environmental surfaces, from the air, or via another person. Based on my experience on the cruise ship, here are some of the ways this can happen:

1. An infected person uses the commode and does not scrub the virus off their hands, touches the hand rails, and another person touches the hand rail, picking up virus particles, and later picks up a dinner roll, transmitting the virus to their own hands, and then ingesting it.

2. An infected person drinks from a glass, shedding a few virus particles into the water, then shares the drink with someone else, who ingests the particles.

3. An infected person vomits, spreading virus particles on surfaces and in the air. Anyone who is in the same room ingests the aerosolized virus particles. Anyone who cleans up the vomit is even closer.

Basically, an infected person spreads the virus everywhere.

Alcohol-based skin cleansers (Purell) are great for disinfecting from many bacteria and viruses, but not norovirus. This virus is completely immune to alcohol. However, it is easily killed by hydrogen peroxide, which is available at any pharmacy or dollar store. Clorox sells it in a spray bottle. You can also cut up some high-quality paper towels and put them in a plastic container with hydrogen peroxide, and use them as wipes.

You cannot prevent norovirus from coming aboard, and you cannot control how it is spread around the ship, but you can protect yourself and your cabinmate.

1. Always wash your hands after using the commode, more thoroughly than you think is necessary. The virus sticks to skin and does not come off with just a brief rinse. Half a minute of washing is best, and that’s a long time compared to what we usually do. Consider yourself a surgeon scrubbing before doing an operation.

2. Spray hydrogen peroxide on all the surfaces you usually touch in your cabin – doorknobs, countertops, bathroom fixtures. Don’t forget the doorknob on the outside of your cabin door.

3. When you head off to meals, spray hydrogen peroxide on your hands and rub them together for a few seconds—don’t dry them off, because it takes half a minute for the virus to die. Then, don’t touch any surfaces at all on your way to meals. Carry a tissue to punch the elevator button.

4. If you see someone pick up food at the buffet and put it back, notify a crew member. Don’t provoke a confrontation with someone, but don’t ignore the public health danger, either. Let the crew members deal with it.

5. Even if you are very careful, you will have touched things that other people have touched—serving utensils, trays, the back of the chair. If you want to be absolutely safe, disinfect your hands just before eating with your hydrogen peroxide wipes.

Norovirus is around everywhere, but the confined quarters of a cruise ship allow for rapid spread from one person to others. If you hear that others have fallen ill, increase your level of prevention. If you do fall ill, report it to ship’s doctor and follow instructions, or you will be the agent of a great deal of misery for others.

For more information, here is the CDC link: http://www.cdc.gov/norovirus/about/index.html

and a very good article in Wikipedia: http://en.wikipedia.org/wiki/Norovirus.