How may Covid19 Tests are conducted daily? Are infection rates in dorms going up or down?



The daily confirmation numbers in Singapore has been going on a yo-yo.



Over the past 8 days from 27 Apr to 4 May, we had daily cases as high as 932 (May 1) and as low as 447 (May 2). On some days, it had created an impression that the situation is improving, while on other days, it seem like the problem would never go away.



Due to the process of testing, the numbers on a daily basis may not reflect the actual state of the infection cases in Singapore. Instead, it will be better to take the number of infection vs the number of tests done as a gauge. Using this measurement, have the infection rate gone up or down in the past weeks?

Let's take a closer look

Analysis
Apr 14 - Apr 27 
Source: MOh
Apr 14 2020
Total Swap Tests: 94 796
Total Unique Person Swap: 59 737
Source: MOH













Apr 27 2020
Total Swap Tests: 143 919
Total Unique Person Swap: 99 929

Between Apr 14 to Apr 27, the number of Swabs Test was at 49,123. That is an average of 3508 tests per day. While the number of tests is useful, the true number of infection would be base on the unique persons swabbed. There are 40,192 unique persons swabbed with an average of 2870 cases per day

Let's take a look at the number of confirmed cases during this period

Apr 14: 224
Apr 15: 447
Apr 16: 728
Apr 17: 623
Apr 18: 942
Apr 19: 596
Apr 20: 1426
Apr 21: 1111
Apr 22: 1106
Apr 23: 1037
Apr 24: 897
Apr 25: 618
Apr 26: 931
Apr 27: 799

Total: 11 485
Total Unique Tests: 40 192
% of infection : 28.5%

Apr 27 - May 4

Source: MOH
May 4 2020
Total Swap Tests: 175 604
Total Unique Tests: 123 525

Between Apr 27 to May 4, the number of Swabs Test was at 31 685. This is an average of 3960 tests per day. There are 23596 unique persons swabbed with an average of 2949 cases per day.

Apr 27: 799
Apr 28: 528
Apr 29: 690
Apr 30: 528
May 1: 932
May 2: 447
May 3: 657
May 4: 573

Total: 5154
Total Unique Tests: 23 596
% of infection: 21.8%


As seen from the numbers, the rate of infection is seen as coming off from 28.5% to 21.8%. However, it had been pointed out that the test focus has shifted from the highly infectious dormitories to dorms with emerging cases.

Some interesting points

  • Testing capacity is said to have increased to 8000 per day. However, base on the numbers presented, average test rates are half of capacity.
  • Average numbers of individual swaps remain similar from 2870 cases from Apr 14-27 to 2949 cases from Apr 27 to May 4.
  • Positive test rates are still high at over 20% over the past weeks. This indicated that the situation at the dorms is not abated.


While we have additional information, a more accurate way to interpret the infection rate would be base on the number of individual tests administered daily. It will be more representative of the trend of infection. For this reason, looking at the numbers on its own on a daily basis would not yield any conclusive analysis on the situation on the ground.


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