Based on a simple analysis of the reports of Sant\'e Public France , we show that the real incidence during the second wave of the Covid-19 outbreak is around 60\% of the mean positivity of virological tests realized week after week in France. The fraction of the French population infected at the beginning of September is about 3\% (2 million people ). Both intensive care units (ICU) admission and death rate , which dropped by more than one order of magnitude since March, are currently 0.017\% and 0.015 \% respectively. Simulations of the outbreak evolution based on the hypothesis of negligible reinfection probability are performed for France, Ile de France, Puy de Dome and Bouches du Rhone . The incidence peak of 3.5 \% is expected at week 39 for France. These values are 4.5 \% at week 37 for Ile de France (for which the peak already passed), 4.2 \% at weeks 41-42 for Puy de Dome, 7\% at week 38 for Bouches du Rhone. The calculated total number of ICU admission and deaths during the second wave are both found around 3000. The cumulative incidence over the two waves is computed close to 50 \% for France and 80 \% for Ile de France. We conclude that Covid-19 is much more spread than previously thought, but its severity became very limited since the end of the first wave . The level of spreading raises doubts in the large-scale testing strategy which anyway detects only a few percents of infected people. It also raises doubts in the efficiency of the closing of school classes, where a pupil is tested Covid-positive by chance. Finally, determining the probability of reinfection by making a large-scale testing of persons already found positive several months ago would strongly help to get a better visibility of the future outbreak trajectory .
Large scale virological testing of SARS-Cov2 is implemented since May 2020 in France. We assume that the positivity of asymptomatic people not being contact cases (ANBC) is representative of the positivity of the whole French population, which allows estimating the real incidence. We estimate, using Sant\'e Public France reports, that the incidence at the beginning of August was about 0.8\% and rose to about 2.4\% of the total population at the beginning of September . This corresponds to about 1.6 million people simultaneously infected and 230.000 new infections each day. These evaluations allow to deduce that intensive care units (ICU) admission rate and infection fatality rate (IFR) dropped by one order of magnitude since March, and are currently 0.036\% and 0.027 \% respectively. Basic simulations of the outbreak evolution based on the hypothesis of negligible reinfection probability are performed for France, Ile de France, Puy de Dome , Bouches du Rhone and Grand Est. These simulations are using a reproduction rate (R) constant over time ranging from 1.3 to 1.45 (1.15 in Grand Est). They use an estimation of the number of infection which occurred during the first wave. These simulations also use the estimated incidence, which by reducing the susceptible population weeks after weeks induces a saturation of the otherwise exponential growth of the outbreak. An incidence peak of 3.5 \% is expected at week 39 for France. The calculated total number of ICU admission and deaths during the second wave are 9000 and 7000 respectively for R=1.3. The cumulative incidence over the two waves is computed close to 60\% for R=1.3 and 70\% for R=1.4. This suggests that if individual immunity exists, herd immunity is likely to be achieved in France by the end of October 2020. We conclude that Covid-19 is much more spread than previously thought, but its severity became limited since the end of the first wave .
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Based on a simple analysis of the reports of
Large scale virological testing of SARS-Cov2 is implemented since May 2020 in France. We assume that the positivity of asymptomatic people not being contact cases (ANBC) is representative of the positivity of the whole French population, which allows estimating the real incidence. We estimate, using
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reports, that
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Covid-19 outbreak is around 60\% of the mean positivity of virological tests realized week after week in France. The fraction of the French population infected
incidence at the beginning of August was about 0.8\% and rose to about 2.4\% of the total population
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is about 3\% (2 million people ). Both
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are currently 0.017\% and 0.015
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Basic simulations
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and Grand Est. These simulations are using a reproduction rate (R) constant over time ranging from 1.3 to 1.45 (1.15 in Grand Est). They use an estimation of the number of infection which occurred during the first wave. These simulations also use the estimated incidence, which by reducing the susceptible population weeks after weeks induces a saturation of the otherwise exponential growth of the outbreak. An incidence
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These values are 4.5 \% at week 37 for Ile de France (for which the peak already passed), 4.2 \% at weeks 41-42 for Puy de Dome, 7\% at week 38 for Bouches du Rhone.
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both found around 3000.
9000 and 7000 respectively for R=1.3.
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50 \% for France and 80 \% for Ile de France.
60\% for R=1.3 and 70\% for R=1.4. This suggests that if individual immunity exists, herd immunity is likely to be achieved in France by the end of October 2020.
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. The level of spreading raises doubts in the large-scale testing strategy which anyway detects only a few percents of infected people. It also raises doubts in the efficiency of the closing of school classes, where a pupil is tested Covid-positive by chance. Finally, determining the probability of reinfection by making a large-scale testing of persons already found positive several months ago would strongly help to get a better visibility of the future outbreak trajectory