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COVID, New: Those infected are hospitalized?

SARSCOV2 infection has a very wide and disparate spectrum of clinical manifestations ranging from completely asymptomatic subjects to subjects with ARDS (acute respiratory distress syndrome) that require intensive treatments and with poor prognosis.

The severity of clinical manifestations is primarily related to the age of the subject and, secondly, with its conhorbidity.

We're seeing an increase in cases. How many of these cases will need hospitalization?
Easy question but whose exact answer is extremely difficult.

To try to respond we can try to look at the situation of European countries that declare the daily number of new COVID hospitalizations.
Italy unfortunately declares only the number of patients total hospitalized.
The number of new daily admissions is available for:


First of all we must make some considerations. We want to have the ratio of hospitalizations / cases but
  • cases have been counted extremely differently depending on the epidemic phases (at the beginning of the epidemic almost only the patients to be hospitalized were tested and the asymptomatic ones did not emerge)
  • hospitalizations arrive late compared to cases.
From 25/3 per 2/9 have been hospitalized in France 108883 covid patients, of which 16872 in intensive care.
In the UK they were hospitalized 128899 Patients, in Belgium 16825 and Denmark 2177.
Important numbers.
From 15/8 per 2/9: Francia 3411 (of which 557 in intensive care), UK 1819, Belgium 398, Denmark 69.
We look at the graphs with data from 25/3 per 2/9: the continuous blue line refers to the weekly moving average of new diagnosed cases, the dotted blue line refers to the moving average of daily hospitalizations, the red line is the ratio of weekly hospitalizations to weekly cases.
What considerations can we make:
  • hospitalizations have never been zero, not even in May and June
  • from the curves of France you can see a delay of about 3 weeks between the increase in cases and the increase in hospitalizations (see the graph in detail, on the left there is the scale of cases, to the right of the hospitalizations).
  • at the beginning of the epidemic, almost only the subjects to be hospitalized were swabbed (in March and April the ratio of hospitalizations /cases was higher than 60% in France and UK).
  • the hospitalization/case ratio changes a lot depending on the epidemic and is reduced in correspondence with a marked increase in cases, situation that may suggest a lower virulence of the infection but probably due only to the delay between cases and hospitalizations.
  • looking at the phases in which, in July, cases remained stable for more than two weeks (green tiles) we see how the percentage of hospitalizations settles on values between the 21% of the United Kingdom, 15% of France, 10% of Belgium and 8% of Denmark. In July all 4 countries had good testing capacity and hospitals in full efficiency. It seems to me the ideal period to get an idea of the real share of hospitalized cases on the total.
  • merging all the data of these 4 countries the ratio of hospitalizations / cases, in the stability period of July, is of the 20%.
  • among the countries I have evaluated only France declares the number of new hospitalizations in intensive care. The ratio between hospitalizations in intensive care and hospitalizations in the wards is quite constant and fluctuates around the 12% .
And’ difficult to have precise estimates but it is very likely that 1000 Today's cases will represent 80-210 hospitalizations between about 3 weeks and the 12% of these hospitalizations will need treatment in intensive care.
These percentages are not so far from what we know about SARSCOV2 from the Literature since the beginning of April: