November 10, 2020 - Probable Cases - A Brief History
Probable Cases - A Brief History
November 10, 2020
COVID-19 finally made the headlines of al.com with the announcement that the Alabama - LSU game is postponed because LSU cannot field at least 53 healthy players due to positive tests and quarantines. When the Auburn - Miss. State game also was postponed, CBS said it will not air an SEC game this weekend. With 1,720 new cases today (incl 577 probables), Alabama surpassed 206,000 cases in all - enough people to fill both Bryant-Denny Stadium and Jordan-Hare Stadium ... with 16,000 to spare.
The addition of just 4,085 tests is the most important news item that will never be noticed.This paltry number means that Alabama is now dead last in the nation in per capita tests for the last 7 days. It also means our one-day positivity rate is a whopping 41.9% and our 7-day rolling average is 20-22%, depending on the tracking service (BamaTracker puts it at 21.22%). There were also 36 more reported deaths.
Hospitalizations continue to rise - 1,206 in 107 reporting hospitals. This is the highest number of patients in Alabama hospitals since August 18. The patients include 190 patients in the Huntsville Hospital Health System (26 in ICU), nearly double the number in early September, and 72 patients at DCH Health (20 in ICU), a 30-patient increase since Friday. The COVID patient populations of both systems are approaching peak levels last seen in July.
Several of you have asked me why the local media are reporting significantly lower positivity rates in Alabama. The answer to this question requires a little background. First, the positivity rate is calculated by dividing positive cases by the number of tests. Second, there are 2 types of tests - PCR tests (examines viral genetic material) and antigen tests (examines proteins on the virus). A PCR test is the gold standard because it can detect the virus before the virus is contagious; however, a PCR test requires the expertise of a lab so it can take longer to get results. The antigen test, developed by Abbott Labs, has a rapid turnaround time and an excellent record for accurately diagnosing positive cases. However, it tends to produce more false negatives than the PCR test.
Over time, antigen tests have grown in popularity because they are less expensive and deliver a rapid result. Last spring, however, the CDC decided that only positive cases confirmed by a PCR test would be deemed “confirmed”; positive cases diagnosed with an antigen test would be classified instead as “probable”. Despite this guidance, most states continued to include antigen positives when calculating positivity.
Then, HHS took over data collection responsibilities from the CDC in July. Almost immediately, HHS began excluding probable cases from the positivity calculation. By excluding “probables” from the numerator of the fraction (reminder: positive cases/ tests = positivity rate) while including the antigen tests in the denominator, the positivity rate was automatically reduced … and, of course, that had the miraculous effect of making public officials look good. Reporters who were too lazy to learn the science simply repeated the artificially low positivity rate they were spoon-fed.
BamaTracker reports the positivity rate both ways - with and without the probables. Johns Hopkins, which is the gold standard data tracker, includes probables, just as I do. Here is the Johns Hopkins site : https://coronavirus.jhu.edu/testing/testing-positivity.
10/28 -1269
10/29 -1443
10/30 -1347
10/31 -1789
11/1 - 1700
11/2 - 907
11/3 - 1037
11/4 - 1848
11/5 - 1381
11/6 - 1556
11/7 - 1768
11/8 - 1205
11/9 - 1190
11/10 -1720
Jefferson County again exceeded 200 cases (229), while Mobile County had 191 and Shelby County 104. Only 5 counties now have 14-day positivity rates under 15% - Bullock (13.0%); Tuscaloosa (13.14%); Lee (13.84%); Elmore (14.68%); and Madison (14.72%).