How many active Covid-19 cases are there?

Multiple sources quote number of Covid-19 daily cases, but information on actual count of patients active at any given moment is rare. ECDC data set I use does not show number of recovered patients, so it is not possible to subtract cumulative recoveries form cumulative cases to calculate number of ill people at any given moment. However we still can estimate number of Covid-19 infected using number of cases.

Estimation method

Whoever contracts Covid1-19 will either recover or die after some time. Let us make the following simple assumption regarding actual illness duration:

  1. Covid-19 patient is ill 14 days from infection date inclusive
  2. Then 7 day recovery period starts and number of infected patients drops linearly

Above rule will give us a set ow weights (see figure below) to be applied to daily cases in order to calculate current number of Covid-19 patients (cases).

Estimation results

Figure below shows estimated number of active Covid-19 cases for selected countries. Only countries above 1 million population were taken into account. Next to country name, in brackets, country all time rank in number of active Covid-19 cases is shown. In order to compare countries with different populations number of Covid-19 ill people (cases) per million is plotted.

  1. Belgium holds all time top in Covid-19 active cases. Czechia is number 2, its curve (in this scale) is similar to Belgium one, we don;t show it to avoid chart overcrowding.
  2. Israel and Qatar had high readings but they have dropped significantly. Israeli drop may be due to lock down imposed on country. I have no details on Qatar lock down policy.
  3. Sweden 2nd wave is much lower than Belgium and other countries, please note Sweden 1st wave was extended over time and the country had distinct lock down policy.
  4. Belgium number of active cases may have peaked, but since Belgium data are delayed (it takes 3 days before all cases are counted) we need to wait a bit in order to confirm this conclusion.
  5. What is happening now in Europe is very similar to Qatar experience, they have survived it so we will too. Unless health services are better organized there…

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