You’d (well, I’d) like to know the population infection rate, but we don’t have enough random testing to justify a number. Current testing remains biased toward those most likely to be infected, so the 15% cumulative rate (total positive / total tested) is certainly a gross overestimate and the 4% daily rate (new positive today / tested today) is still biased upward..
We figure the real population rate is well under 4%, which means we don’t encounter many infected folks out there.
A number of state are now “opening up” without worrying about the details. Because exponential growth starts very slowly and the dying begins three weeks after the infections, the CNN charts (near the bottom of the page) will be revealing; we’ll witness several large-scale epidemiology experiments in real time over the next few months.
I think if any single action other than a virus killed 100,000 US citizens in three months, there wouldn’t be nearly as much discussion about the correct response. On the other paw, COVID-19 still runs a little under the rate for heart disease, so it seems we can get used to dying, even in bulk, when we do it long enough.
The bulk of the subsequent increase comes from the Fu Mask Templates, although I suspect folks aren’t looking for 3D printed stuff.
As far as my original predictions go, I’m pleased to be somewhat wrong, as the most recent data shows the effect of handwashing, distancing, and general paranoia:
The lowered slope in the Total Cases curve means the cases now increase by a factor of ten every 20 days, rather than every eight, which is a major improvement. Still, it implies whatever seems bad right now will be only 10% of the badness in three weeks.
They assume “full social distancing through May 2020” and, apparently, the virus vanishing thereafter.
The colored area represents the 95% uncertainty range. Among other things, we don’t know what will happen when the (unknown number of) currently infected people need (far) more medical care / equipment / resources than we have available (“open image in new tab” for more dots):
Given our somewhat … erratic … national leadership, keeping everybody tucked in and the economy turned off for any substantial duration seems unlikely, but there’s no other way to reduce the death toll. The vast majority of the population will not have been exposed to COVID-19 and will, therefore, remain vulnerable to any (infected-but-asymptomatic, thus untested) people arriving from other counties / states / countries.
A local hospital contacted Mary’s quilting group to sew up cloth covers to prolong the life of their medical-grade N95 masks. Their recommended pattern, the Fu Face Mask from the FreeSewing group, comes in three sizes:
N.B.: Use their original PDF, because a JPG picture probably won’t come out at the right size.
Also N.B.: Used by itself, this is not a medical-grade filter mask.
The patterns do not include the usual 1/4 inch seam allowance around the outside, so I cranked out 3D printed plastic cutting templates.
If you’re not interested in 3D printing, 2D print the PDF file on cardboard, sketch a seam allowance, and cut it out, as quilters have been doing since slightly after home printers happened.
The plan of attack:
Convert mask outlines into a bitmap image (GIMP)
Create Bezier curves by tracing outlines (Inkscape)
Save curves as SVG files
Convert SVG into solid model (OpenSCAD)
Add stiffening ribs &c
Save as STL solid model
Slice into G-Code file (Slic3r)
Fire the M2!
So, we begin …
Import the PDF into The GIMP, delete the text & suchlike, convert to monochrome, and save the pattern outlines as a PNG file:
It turns out Inkscape can directly import the PDF, but it valiantly tries to convert all the text and the incidental graphic elements, none of which will be useful in this situation. It’s easier to delete them in The GIMP and make a bank shot off a PNG file.
Import the PNG into Inkscape and trace one outline with the Bezier curve tool:
If you squint really carefully, you’ll see Bezier control handles sticking out of the nodes. I laid three nodes along the top arc and four along the right side, but do what’cha like; the Insert key or Shift+I inserts and Delete removes nodes. It’s easier to center a node in the middle of the PNG line with snapping turned off: Shift+drag while mousing or globally with #.
You could unleash the bitmap auto-tracer, but it generates a bazillion uselessly tiny Bezier curves.
When you’re happy, select and copy the path with Ctrl+C, paste it into a shiny new Inkscape document (Ctrl+N) with Ctrl-V, save it with a catchy file name like Fu Mask - Small - nominal.svg, and close that document to return to the document with the PNG outlines and the original path.
Select the original path again, create a dynamic offset with Ctrl+J, open the XML editor with Ctrl+Shift+X (which automagically selects the proper SVG element), and change the inkscape:radius value from 0 to 6.35 (mm, which everyone should use) to get a 1/4 inch seam allowance:
The path will puff out with curved corners:
Copy into a new document, save as Fu Mask - Small - seam allowance.svg, and close.
Repeat that process for each of the three mask sizes to create three pairs of SVG files: the nominal mask outline and the corresponding seam allowance outline for each size.
The OpenSCAD program imports the SVG files, removes the nominal outline from within the seam allowance to leave the outline, adds stiffening ribs, and stamps an ID letter on both sides of the central button:
Choose one of the three sizes with the OpenSCAD customizer, save the resulting model as an STL file, repeat for the three sizes, and you’re done.
This process can convert any outline paths in SVG files into cutting templates, so, should the Fu Mask not suit your fancy, Use The Source.
Gut a new package of wipes: 552 g total weight, with 80 wet wipes weighing 536 g, so the packaging amounts to 15.5 g and each wet wipe weighs 6.7 g.
Hang five wipes in the breeze for a few hours to find they weigh 9.2 g. They’re still slippery, because of all the aloe & Vitamin E & whatever else Amazon specifies for the mix, but they’re dry. One dry wipe weighs 1.8 g, so all 80 weigh 150 g.
The block o’ wet wipes holds 536 – 150 = 390 g = 390 ml of water.
Should you want a 70% (by volume) isopropyl alcohol solution, pour 0.7/0.3 × 390 ml = 910 ml of 99% alcohol into the package and let it settle for a while. Each wipe will emerge dripping wet, but that’s not entirely a Bad Thing. Perhaps it’d be a good idea to start by letting the block dry out for a while, re-weigh, then calculate the alcohol dose from the reduced amount of water.
Bleach dilutions for sanitation seem wildly varied, but the jug of 8.25% sodium hypochlorite on the shelf says 1/2 cup to a gallon, a 1:32 volume ratio. Starting with 390 ml of water-like substance in the package, pour 12 ml of bleach into the hatch, let things settle, then squish it around for good measure.
None of the dosages seem particularly critical, given the slapdash way everybody applies wipes.
You should, of course, conspicuously mark the packages, so as not to apply toxic wipes to sensitive parts of you or your baby …
The penciled lines give an eyeballometric fit, but it’s pretty obvious the USA is now dealing with purely exponential infection rates.
Total Cases, which is the patients tested = people already in the medical system, is growing by a factor of ten every eight days. By next weekend, the USA will have one million Total Cases: average it to 112,000 new cases, every day,over the next eight days.
Which may not happen, if only because we may not have the intake / testing / recording capacity for that number of patients and maybe, just maybe, Social Distancing will have an effect. I expect the Total Cases line bend downward slightly during the week, but it won’t be anywhere near horizontal. Obviously, the extrapolation fails completely within the next 24 days, because we lack a factor of 1000 more people to infect.
The 9,000 patients who will die in the next week are already in the medical system (because you take about two weeks to die) and, at least in downstate NY, have essentially filled all available hospital beds; they’re getting the best care possible from the medical establishment.
Not every new case becomes a patient, but in the USA we seem to be testing only folks with obvious COVID-19 symptoms, so all the optimistic hospitalization estimates of 10% are off the table and 50% seems more believable. Pick any percentage you like.
Eight days from now, the rate will ramp toward 10,000 deaths per day, to reach 100,000 Total Deaths in sixteen days, again, as an average.
The current recommendation: remain home unless and until you develop COVID-19 symptoms requiring urgent medical attention. Should that happen to me, I fully expect there will be no medical attention to be found and, certainly, all available medical equipment will be oversubscribed.
Speaking strictly as an Olde Farte looking at the data, the future looks downright grim.
On the upside, it’s amazing how little an order to remain home changed my daily routine: so many projects, so little time.