1. Portada
  2. Notificación de casos de covid-19 en la Comunidad de Madrid
  3. Distribution of delayed notifications

Distribution of delayed notifications

Figures 1-3 make it clear that the number of positive covid-19 cases occurred in CM on any given date between the beginning of the pandemic and the end of the third wave (mid-December 2020) was only known weeks or months later. One other way to look at the pace of notification consists of identifying the date to which newly-added old cases are assigned in the report published by CM on any given date. Figure 4 shows a prototypical example pertaining to the case-to-date assignment of newly-added cases in the Dec 10th, 2020 report. Although the largest numbers occur over the 7–10 days immediately preceding the date of the report, the vast majority of the 1005 newly-added cases were assigned to dates broadly spread across the entire pandemic period since early March 2020. This particular report also removed four of the cases included in earlier reports.

 

 

Figure 5 shows analogous graphs for the case-to-date assignment of newly-added cases in each of the reports published by CM between May 14th, 2020 (the date on which CM published its second report) and the date on which this page was last updated. This series of graphs reveals four distinctly different periods as regards the assignment of dates to newly-added cases:

  • Between May 14th and June 18th, 2020. Over this period, newly-added cases are relatively scarce and they are assigned approximately evenly to dates across the preceding two or three months.
  • Between Jun 19th and Dec 24th, 2020. Over this period, newly-added cases are numerous and they are mainly assigned to dates far back along the entire pandemic period, as shown in Figure 4. Removal of cases included in earlier reports is relatively scarce, with some remarkable exceptions (see the graphs pertaining to Aug 31st and Sep 1st, 2020 on pages 23 and 24 in Figure 5).
  • Between Dec 26th, 2020 and Apr 16th, 2021. Over this period, newly-added cases are mainly assigned to dates within the 15 days prior to the date of the report. Each report also adds and deletes a meaningful number of cases on dates far back along the entire pandemic period.
  • From Apr 17th, 2021 onward. Over this period, a meaningful fraction of newly-added cases are assigned relatively evenly to dates ranging from 15 days to two months prior to the date of the report. Addition and deletion of cases far back along the entire pandemic period continues. Figure 6 shows three prototypical examples.

 

 

The daily addition and deletion of old cases in CM reports published since late Dec 2020 seems to affect past dates haphazardly (see Figures 5 and 6). Nevertheless, these small but daily modifications produce a non-negligible aggregated effect. Figure 7a shows how modifications introduced in the CM reports published during the 90 days prior to the latest update of this page have changed upward (in blue) or downward (in red) the count of cases acknowledged on dates 120 or more days back from the date in which this page was last updated. The weekly summaries tab describes the distribution of the relatively large numbers of old cases added or deleted by CM on a week-by-week basis. Figure 7b shows the number of cases altered more than 90 days after their nominal date of occurrence throughout the pandemic period.