Creek Running North

Sorry I haven’t posted much the last few days: I’ve been busy with a project. You know about RNA, right? Ribonucleic Acid, the substance we use as a template to translate information from genes into proteins? Well I got a hold of a short, very dangerous sequence of RNA — only about 7,000 base pairs long, nothing really — that’s really hard to destroy once it gets out into the world, and for the last few days I’ve been replicating it, making millions of copies, and releasing them into the environment. 

Of course, I didn’t want to.

That single strand of RNA belongs to a norovirus, the main culprit responsible for what’s often called “stomach flu,” which is not at all related to influenza. At least I think that’s what it was. I didn’t run the necessary tests, which involve detecting viral proteins in the patient’s stool. I was kind of distracted at the time. Still, widespread outbreak of norovirus in the country the past few months, enough cases in the Bay Area lately that Becky brought a related public notice home from school, and the symptoms matched well enough — though thankfully the nausea was mostly limited to a an unsettling queasiness, as if someone had just given me a Qiana shirt for the holidays.

At least with gastroenteritis not involving nausea, you can catch up on your reading. If you don’t have a week-long headache from dehydration and caffeine withdrawal. Which I did. At least by Thursday, I was able to persuade Zeke he wanted to go down to the park for a little while, and then I was almost able to carry him back. Don’t you tell me I didn’t accomplish anything this week.

Noroviruses are one of four genera in the family Calicivirus, which also includes the milder-gastroenteritis-causing Sapoviruses, which I will ask for instead next time, and the fatal-hemorrhagic-fever-inducing Lagoviruses that Australian farmers use to wreak genocide on rabbits, and the Vesiviruses, which cause swine vesicular exanthema, in which pigs grow little hard painful carbuncles all over and lose their foot pads. Which grow back when the pigs recover. Caliciviruses are so-called because their crystalline protein covers, which protect the RNA inside from stray enzymes, often have little depressions in them: “chalices.” Those protein covers are sturdy, withstanding freezing, heating to 140°F for half an hour, and easily allowing the viruses to survive the chlorination levels found in most tap water. Vesiviruses in pork can even survive the meat being smoked. You know all those barbecue joints in the South with signs showing happy pigs in chef’s hats getting ready to eat a rack of ribs? Probably not the best idea from a pig health viewpoint.

I mention the survivability of viruses, but “survive” isn’t really the right word: there’s dispute as to whether viruses are actually alive. In order to reproduce, viruses must commandeer the metabolic machinery of living cells and use them to replicate their own genetic information and crunchy outer shell. When the viruses kill the cell in the process — which doesn’t always happen — and the process is repeated enough times, disease results.

Noroviruses invade cells deep in our gut lining, resulting among other things in damage to the mucous lining of the intestinal portion GI tract, which causes fluid to leak into said tract and prevents it from being reabsorbed, with predictable results. (The same damage upsteam in the stomach causes nausea.)

But surprisingly, given the fact that norovirus-related gastroenteritis is one of the most common pathogenic diseases of humans in the developed world, the precise route by which the viruses get to those gut cells is a mystery. This is partly because unlike other pathogenic viruses, caliciviruses are really difficult to culture in the lab. Noroviruses weren’t cultured successfully until 2004.  The norovirus used in that experiment, a strain that infects mice, had only been discovered the year before. The researchers who were able to grow Murine Norovirus 1 (MNV-1) in the lab found that the virus seemed to target dendritic cells, immune-system cells found in the lining of the intestines and stomach. If human noroviruses do the same, the dendritic cells may provide entrance to the interior of the GI lining. MNV-1 also went for macrophages, another type of cell involved in the immune system. If you think of them as white blood cells that have rooted out into the surrounding terrain, you won’t be too far off.

However the virus gains entrance to the gut lining, the effects are unpleasant, and we start shedding millions of viruses out both ends of our GI tracts.* Ingest as few as 100 individual viruses — and that’s how you contract it, mainly: by eating them — and one or two days later, you’re thinking a couple days without eating sound like a very good idea, and savoring the delicious coolness of the bathroom floor on your forehead.

But I’m feeling much better now.

* Look, I know reading about vomit and loose stool is less than pleasant, but look at it this way: I could be writing about the latest pile-on blowup in the progressive feminist blog world. Projectile vomiting is kind of a nice respite from those, I’m thinking.