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Vaccine data is from the Centers for Disease Control and Prevention and may differ from data provided by the Alabama Department of Public Health.
Different trackers have different cut-off times and tracking methods, so daily case totals may be slightly different. There are three main tracking methods for Alabama’s case data. (1) Cases by date of infectiousness, (2) cases by date reported to ADPH, and (3) a raw tracking of the cumulative case count.
For most of the pandemic, through the summer of 2021, APR’s dashboard relied on the third method (3), meaning that our dashboard captured the cumulative case count (the total number of cases since March 2020) for each day as publicly posted on ADPH’s data portal. The previous day’s cumulative case count was then subtracted from the current day’s count to arrive at a daily increase. For example, the cumulative case count on Jan. 17, 2021, was 422,598. The count on Jan. 18, 2021, was 424,028. Therefore, the case increase on Jan. 18 was listed as 1,430. Other than some ad hoc accounting for backlogs, the data isn’t revised later.
The second method (2) is similar except that it relies on internal counts provided by the Alabama Department of Public Health. The “date reported” represents when the case was reported to ADPH by a health care provider. If ADPH receives 5,000 case reports on a day, that day’s case increase will be listed as 5,000, regardless of when the case actually occurred. Counts are typically very close to the first method (1), except for some fluctuation caused by delays. ADPH doesn’t adjust this data when backlogs are reported, so some dates have data anomalies caused by that.
The first method (1) tracks cases by the date the case occurred — in other words, when the case became infectious or ill. This count differs from the “date reported” because there are sometimes delays or backlogs between when a case occurs and when a provider reports that case to ADPH. There have been instances throughout the pandemic when labs and other providers have neglected to report cases immediately. For instance, a single lab could report 5,000 cases on Dec. 15. Once inspected, it’s determined those cases occurred in October and November. ADPH will backdate each case to the date it occurred. This method accounts for backlogs better than that second (2) and third (3). However, this method has lag. Data for the last two weeks — and occasionally longer — are often incomplete because of the time it takes providers to report cases to ADPH and for ADPH to determine and record the date of occurence. That’s why on the daily case count chart of cases by date of infectiousness, it frequently looks as if the daily case counts for the last few days have taken a sudden dive. That is usually because the data is incomplete. As time goes on, ADPH receives more reports and updates daily numbers, and the numbers are typically revised upward.
The same three methods are used for deaths as well, i.e. deaths by actual date of death, deaths by date of report, and a raw tracking of the cumulative death count.
ADPH uses the first method (1) for monitoring COVID-19 cases and trends as it is a more accurate representation of disease transmission levels in the community than the second method (2). Beginning in July and August of 2021, APR removed method three (3) from our dashboard. Now, we rely on the data provided by ADPH and provide both method one (1) and method two (2) tracking in several categories. However, we still perform other calculations on our own based on ADPH’s data.