% Positive New Cases Per Day
It’s time to show some numbers of my own!
Thanks to The Seattle Times and the Washington State Department of Health (DOH), I have built a table that summarizes COVID-19 case statistics since late February. Data before March 10 is somewhat spotty and lacks the number of tests per day, etc. The raw numbers are shown in the table below.
Cum Cum Cum
Date Positive Negative Tests New Cases New Tests Ratio Notes
------ -------- -------- ------- --------- --------- ----- --------
Feb 28 1
Feb 29 7
Mar 2 18
Mar 4 39 SnoEmerg
Mar 5 70 Pence
Mar 6 83
Mar 7 102
Mar 8 136
Mar 9 162 1149 1311
Mar 10 267 105
Mar 11 366 3037 3403 99 Ban>250
Mar 12 457 4350 4807 91 1404 6.48%
Mar 13 568 6001 6569 111 1762 6.30%
Mar 14 643 7122 7765 75 1196 6.27%
Mar 15 769 9451 10220 126 2455 5.13%
Mar 16 904 11582 12486 135 2266 5.96% HomeRec
Mar 17 1012 13117 14129 108 1643 6.57%
Mar 18 1187 15918 17105 175 2976 5.88%
Mar 19 1376 19336 20712 189 3607 5.24%
Mar 20 1524 21719 23243 148 2531 5.85%
Mar 21 1793 25328 27121 269 3878 6.94%
Mar 22 1996 28879 30875 203 3754 5.41% Everett
Mar 23 2221 31712 33933 225 3058 7.36%
Mar 24 2469 248 StayHome
Mar 25 2580 111
Mar 26 3207 43173 46380 627 12447 7.92%
Mar 27 3700 49015 52715 493 6335 7.78%
Mar 28 4300 54896 59196 600 6481 9.26%
Mar 29 4896 60566 65462 596 6266 9.51%
Mar 30 5515 DOHIssues
Mar 31 5984 68814 74798 1088 9336 11.65%
Apr 1 6585 72833 79418 601 4620 13.01%
Apr 2 6966 75633 82599 381 3181 11.98%
Apr 3 7591 80327 87918 625 5319 11.75%
Apr 4 7984 393 DOHIssues
Apr 5 8384 400
Apr 6 8682 298
Apr 7 9097 415
Apr 8 9609 512
Apr 9 9887 278
Apr 10 10224 337
Apr 11 10411 187
Apr 12 10538 127
Apr 13 10694 112160 122854 166
Apr 14 10783 113500 124283 89 1429 6.23%
Apr 15 11152 117748 128900 369 4617 7.99%
Apr 16 11445 120182 131627 293 2727 10.74%
Apr 17 11802 135706 357 4079 8.75%
Apr 18 11790 126852 138642 2936 DOHCorrection
Apr 19 12085 128926 141011 295 2369 12.45%
Apr 20 12282 132749 145031 197 4020 4.90%
Apr 21 12494 135459 147953 212 2922 7.26%
Apr 22 12753 140623 153376 259 5423 4.78%
Apr 23 12977 147347 160324 224 6948 3.22%
Apr 24 13319 157275 170594 342 10270 3.33%
Apr 25 13521 161956 175477 202 4883 4.14%
Apr 26 13686 165993 179679 165 4202 3.93%
Apr 27 13842 168673 182515 156 2836 5.50%
Apr 28 14070 173730 187800 228 5285 4.31%
Apr 29 14327 179654 193981 257 6181 4.16%
Apr 30 14637 184087 198724 310 4743 6.54%
May 1 15003 192312 207315 366 8591 4.26%
May 2 15185 196820 212005 182 4690 3.88%
May 3 15462 200858 216320 277 4315 6.42%
May 4 15594 203859 219453 132 3133 4.21%
May 5 15905 208908 224813 311 5360 5.80%
May 6 16231 214449 230680 326 5867 5.56%
May 7 16388 219447 235835 157 5155 3.05%
May 8 16674 226315 242989 286 7154 4.00%
May 9 16891 231984 248875 307 5886 5.22%
May 9 16891 231984 248875 307 5886 5.22%
May 10 17122 234986 252108 231 3233 7.15%
May 11 17330 238991 256321 208 4213 4.94%
May 12 17512 243568 261080 182 4759 3.82%
May 13 17773 250158 267931 261 6851 3.81%
May 14 17951 255352 273303 178 5372 3.31%
May 15 18288 262705 280993 337 7690 4.38%
May 16 18433 266810 285243 145 4250 3.41%
May 17 18611 270524 289135 178 3892 4.57%
May 18 18811 274309 293120 200 3985 5.02%
May 19 18971 278971 297942 160 4822 3.32%
May 20 19117 283810 302927 146 4985 2.93%
May 21 19265 289093 308358 148 5431 2.73%
May 22 19585 296691 316276 320 7918 4.04%
May 23 19828 306765 326593 243 10317 2.36%
May 24 20065 310533 330598 237 4005 5.92%
May 25 20181 312610 332791 116 2193 5.29% George Floyd
May 26 20406 315395 335801 225 3010 7.48%
May 27 20764 322327 343091 358 7290 4.91%
May 28 21071 327162 348233 307 5142 5.97%
May 29 21349 333005 354354 278 6121 4.54% SEA protests
May 30 21702 339197 360899 353 6545 5.39%
May 31 21977 343295 365272 275 4373 6.29%
Jun 1 22157 346642 368799 180 3527 5.10%
Jun 2 22484 354843 377327 327 8528 3.83%
Jun 3 22729 360858 383587 245 6260 3.91%
Jun 4 22993 367870 390863 264 7276 3.63%
Jun 5 23442 377146 400588 449 9725 4.62%
Jun 6 23729 381327 405056 287 4468 6.42%
Jun 7 24041 386249 410290 312 5234 5.96%
Jun 8 24354 390700 415054 313 4764 6.57%
Jun 9 24642 --- --- 288 --- ---
Jun 10 24779 400433 425212 137 10158 4.18%
Jun 11 25171 414691 439862 392 14550 2.69%
Jun 12 25538 424608 450146 367 10284 3.57%
Jun 13 25834 436768 462602 296 12456 2.38%
Jun 14 26158 445107 471265 324 8663 3.74%
Jun 15 26531 453495 480026 373 8761 4.26%
Jun 16 26784 408232 435016 253 --- --- DOH no sero
Jun 17 27192 419707 446899 408 11883 3.43%
Jun 18 27601 428340 455941 409 9042 4.52%
Jun 19 28225 437844 466069 624 10128 6.16%
Jun 20 28680 446258 474938 455 8869 5.13%
Jun 21 28870 448334 477204 190 2266 8.38%
Jun 22 29386 457673 487059 516 9855 5.24%
Jun 23 29869 465629 495498 483 8439 5.72%
Jun 24 30367 475428 505795 498 10297 4.84%
Jun 25 30855 483573 514428 488 8633 5.65%
Jun 26 31404 494398 525802 549 11374 4.83%
Jun 27 31752 502691 534443 348 8641 4.03%
Jun 28 32253 515967 548220 501 13777 3.64%
Jun 29 32824 524451 557275 571 9055 6.31%
Jun 30 33435 538529 571964 611 14689 4.16%
Jul 1 34151 550838 584989 716 13025 5.50%
Jul 2 34778 565197 599975 627 14986 4.18%
Jul 3 35247 572029 607276 469 7301 6.42%
Jul 4 35898 576808 612706 651 5430 11.99%
Jul 5 36985 592271 629256 1087 16550 6.57%
Jul 6 37420 598104 635524 435 6268 6.94%
Jul 7 37941 607131 645072 521 9548 5.46%
Jul 8 38581 621749 660330 640 15258 4.19%
Jul 9 39218 629248 668466 637 8136 7.83%
Jul 10 ---
Jul 11 40656 645349 686005 1438 17539 8.20%
Jul 12 41757 666517 708274 1101 22269 4.94%
Jul 13 42304 675930 718234 547 9960 5.49%
Jul 14 43046 690840 733886 742 15652 4.74%
Jul 15 44313 708861 753174 1267 19288 6.57% Yakima backlog
Jul 16 45067 722590 767657 754 14483 5.21%
Jul 17 46026 745760 791786 959 24129 3.97%
Jul 18 46946 762393 809339 920 17553 5.24%
Jul 19 47743 778611 826354 797 17015 4.68%
Jul 20 48575 792609 841184 832 14830 5.51%
Jul 21 49247 805905 855152 672 13968 4.81%
Jul 22 50009 820754 870763 762 15611 4.88%
Jul 23 50824 833158 883982 815 13219 6.17%
Jul 24 51849 851825 903674 1025 19692 5.21%
Jul 25 52635 866712 919347 786 15673 5.01%
Jul 26 53321 879983 933304 686 13957 4.92%
Jul 27 54205 891029 945234 884 11930 7.41%
Jul 28 54985 903322 958307 780 13073 5.97%
Jul 29 55803 917851 973654 818 15347 5.33%
Jul 30 --- DOH outage
Jul 31 57541 943987 1001528 1738 27874 6.24%
Aug 1 58173 950107 1008280 632 6752 9.36%
Aug 2 58715 --- 542 DOH issues
Aug 3 59379 --- 664
Aug 4 60084 --- 705
Aug 5 60917 --- 833
I have tried to make this table as accurate as possible. Please forgive any transcription errors. The Washington Department of Health has suffered technical issues, so there are gaps in the data. Their database has been overwhelmed and they have had trouble tallying negative test results and the number of tests.
Don’t forget about the University of Washington Virology Laboratory COVID-19 dashboard as another reliable data source.
The State DOH reports the cumulative number of positive cases (tests) negative test results daily — the second and third columns in the table. The fourth columb, cumulative number of tests, is the sum of the cumulative positive and negative results each day.
From these numbers, we can compute the number of new positive cases and the number of new tests for each 24 hour period:
Tests.Today = Positive.Today + Negative.Today
New cases = Positive.Today - Positive.Yesterday
New tests = Tests.Today - Tests.Yesterday
Ratio = (New cases / New Tests) * 100.0
The seventh column, ratio, is the percentage of positive new cases per day. I believe that this percentage is an appropriate measure for tracking COVID-19 over time. The ratio normalizes the number of positive cases for the number of tests performed. Thus, it makes daily results comparable even as our test capacity and number of daily tests grow.
Update: Washington State calls this ratio/percentage “Positivity Rate.”
The bar chart below is a quick and dirty plot of the daily percentage of positive cases over the last ten days. Be sure to check the vertical scale when interpreting the chart!
I hope this trend declines. Please remember that any measurements taken today show what COVID-19 was doing 10 to 14 days ago. The delay is due to the time required for COVID-19 incubation, worsening of symptoms, clinical presentation and testing.
The last column in the table, Notes, are my mental notes marking significant events along the COVID-19 timeline in our area. The events are:
- Snohomish County (my home) declares a state of emergency.
- Vice President Pence visits the State of Washington.
- Governor Inslee bans groups of more than 250 people.
- The State advises people to stay at home, especially the elderly.
- The City of Everett (a stone’s throw away from home) imposes a stay at home order.
Up to today, Governor Inslee has not imposed a blanket “stay at home” order. Suggestions made by the state are similar to a stay at home order, but do not have the force of law.
Don’t do this
Here is the egregious chart of the day by way of Cleveland.com. I still check in with my original hometown. Hope the Cavs can hit the court again.
To be fair, the author did put a few caveats about number of tests, etc. in the article. The caveats are lost in the TL:DR age. Please don’t publish meaningless charts and comparisons.
If I were teaching a math or science class today, I think I would use this chart in class about critical thinking and interpetation of the graphs thrown at us by the media.
No one (CNN, etc.) should compare state-by-state number at this point in time. There isn’t a standard for reporting and test capacity is, literally, all over the map.
Stay distant and stay healthy — pj