With two cruise ships returning to port last week after having been boarded by the Dread Pirate Projectile Vomiting, people are once again referring to cruise ships as "floating Petri dishes." The comparison is both unfair and inaccurate, since Petri dishes don't offer options like karaoke, video slots, skeet shooting, and pool recreation, and Petri dish buffet spreads are notoriously monotonous -- usually some kind of broth and agar mix.
As the passengers return home to recover, the CDC and cruise lines go to work trying to figure out the details of this latest high-profile outbreak of norovirus, aka "the stomach flu" or "the cruise ship virus."
Those two nicknames are misleading, however, because the hallmark flu symptoms -- high fever, severe muscle aches, sore throat and dry cough -- are typically much different than norovirus's profoundly gastrointestinal symptoms. (For clarity in public health messaging, I am lobbying the CDC to rename norovirus as the "Pukes-'n-Squirts virus." No word yet.) And although it's true that norovirus can spread quickly aboard the intimate confines of a ship, "the cruise ship virus" happens to be the predominant cause of pukes-'n-squirts in land-based outbreaks. In other words, this pirate does most of its damage in port. When "it's going around" at school or in a nursing home, "it" is usually the norovirus.
In March of 2011, the CDC published an update on the science of norovirus. Historically, we've never understood this virus very well, because it's been impossible to grow in a culture -- even in a "floating Petri dish" (another way in which the slur is inaccurate). It's difficult to study what you cannot even "see," but newer technology has allowed us to document its presence and therefore investigate its behavior. Points of interest from the update include:
- This sh#t is more infectious than the mood at a Taylor Swift concert: An acutely-infected person can have as many as 100 billion viral copies in a gram of stool, and it takes as little as 18 viral copies to become ill. Virus comes out of both ends, but diarrhea is thought to be more infective than vomit.
- Current CDC guidelines advise passengers and crew who are ill to stay in their cabins until they are feeling better and it's been 24 hours since their last episode of diarrhea or vomiting. This might keep people off the promenade deck during their most miserable, most transmissible period, but peak viral shedding occurs for two to five days after infection, and the virus can be detected in stool for an average of four weeks following infection. To complicate matters, 30 percent of infections appear to be asymptomatic, and asymptomatic persons can shed virus, albeit at lower numbers than symptomatic persons. So it's hard to keep a lid on an outbreak -- be it on the high seas, or at Sunshine Acres -- when you don't know exactly who to quarantine.
- Even though bacteria like E. Coli and Salmonella (King Nut peanut butter) get all the press, it's norovirus that causes the majority of food-related outbreaks of dysentery. Because there is no animal reservoir for norovirus, we can't blame the chickens or the cows or the pigs for contaminating our food. Infected food handlers do us in, particularly if they're preparing raw foods (do you like piña coladas, and getting caught in the rain?) or foods that are presented as "ready-to-eat."
- Although norovirus is highly infective, it cannot drill through your skin. You have to provide round trip transportation to your mouth, either with the food you eat, or the things that you touch with your hands -- and then bring to your mouth. Ever been to a self-service café where the silverware sits mouth-side-up in a bin, with the handles down? That's backwards.
- Hand washing with soap and water for at least 20 seconds is the most effective way to reduce norovirus contamination on the hands; you're not killing them so much as washing them off. The CDC is beginning to move away from recommending the use of hand sanitizers for norovirus. Because the efficacy of sanitizers is questionable for norovirus, they can deliver false assurances to users, and should not be used as a substitute for washing with soap and water.
- Once you've contracted a particular cold virus strain, you won't get it again. Not so with norovirus. You can definitely get re-infected with the same strain somewhere down the line. A few people will develop protective antibodies that last for several months, but many will not.
- And let's end with a fact that I find deeply disturbing: A small portion of the population -- about 20 percent of whites for example -- appears genetically resistant to norovirus infection. This is not even fair. On behalf of those of us who've ever found ourselves lying on the bathroom floor, moaning softly as the coolness of the tile on our face fans the last ember of our will to live, I would ask that these people be rounded up by CDC officials and deported to a remote island, where they will be forced to make tasty, ready-to-eat meals for shipment to recovering norovirus victims. They can be released when they're ready to apologize, or at least empathize, as best they can. After all, they don't know what they're missing.
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