Dödligt virus från Kina orsakar panik (SARS-CoV-2, COVID-19)

Abstract

We develop and apply a simplified SIR model to current data for the 2019-2020 SARS-Cov-
2/Covid-19 pandemic for the United Kingdom (UK) and eight European countries: Norway, Sweden, Denmark, the Netherlands, France, Germany, Italy and Spain. The most important result of the model was the identification and segregation of pandemic characteristics into two distinct groups: those that are invariant across countries, and those that are highly variable. Amongst the
former is the infective period �𝐿 , which was very similar for all countries, with an average value
of �𝐿 = 15.5 +/- 0.6 days. The other invariants were �� , the average time between contacts and
� = 𝑁� , the average number of contacts while infective. We find �� = 3.5 +/- 0.2 days and
𝑁� = � = 4.46+/- 0.17. In contrast to these invariants, there was a highly variable time lag ��
between the peak in the daily number of infected individuals and the peak in the daily number of
deaths, ranging from a low of �� = 4 days for Italy and Denmark, to a high of �� = 17 for Norway.
The mortality probability among identified cases was also highly variable, ranging from low values
3.5%, 5% and 5% for Norway, Denmark and Germany respectively to high values of 18%, 18%
and 20% for France, Sweden and the UK respectively. Our analysis predicts that the number of deaths per million population until the pandemic ends (defined as when the daily number of deaths is less than 5) will be lowest for Norway (45 deaths/million) and highest for the United Kingdom (628 deaths/million). Finally, we observe a small but detectable effect of average temperature on
the probability 𝛼 of infection in each contact, with higher temperatures associated with lower
infectivity.

A comparison of cases and deaths among the countries.

A direct comparison of the cases and deaths among these none countries can be made by plotting
the normalized fractions 2 (&#119905 = 𝑋2 (&#119905/𝑁 and 4 (&#119905 = 𝑋4 (&#119905/𝑁 on the same scale (Figures 8,9), with the parameter 𝑁 obtained from the fits described above. These results show that:

• Among the N-Eu countries, although the pandemic started at about the same time, the initial
normalized case growth rates in Norway and Sweden were higher (Figure 8a), because of the
higher value of 𝛼 discussed previously (Figure 6c).

• In all countries other than Sweden and the UK, 2 (&#119905 is decreasing after reaching a peak.
However, in Sweden and the US, it has merely plateaued (Figures 8a, 9a), suggesting that our
predictions for the total number of cases in these countries (Table I) are likely to be
significantly underestimated. In Sweden and to some extent also in the UK, 4 (&#119905 is not
declining after reaching a maximum value (Figure 8b, 9b), suggesting that our estimates for
the total number of deaths in these countries may also be significant underestimates.

• In the S-Eu countries and UK, the pandemic began first in Italy and last in the UK (Figure 9a).
The peaks in cases in all the S-EU countries happened at about the same time with similar
values for 2 (&#119905 at the peak. However, in the UK, there was no peak in 2 (&#119905 but rather a
plateau, as in Sweden.

• In spite of similar normalized cases 2 (&#119905 for all countries, Germany and Norway had the smallest normalized deaths 4 (&#119905.

• The peaks in 4 (&#119905 happened at significantly different times for the nine countries investigated
(Figure 8b, Figure 9b), verifying the differences in , the time delay between identification
of disease and death (Table I), which was shortest for Italy and Denmark (4 days) and highest
for Norway (17 days).