Home confinement measures are leading to turning point

If the current social distancing measures are maintained for about ten days, it might be possible to relax the restrictions

The tight restrictions on everyday life appear be having the desired effect. In Germany, the daily case numbers give cause for optimism. And according to a model calculation by researchers at the Max Planck Institute for Dynamics and Self-Organization, this is due to the extreme social distancing measures that have been in effect since March 22. According to the simulation, such measures have curbed the dreaded exponential spread of Covid-19. The simulation of the Göttingen team had already proven the effect of the restrictions of 8 and 16 March; however, these had not yet weakened the exponential curve of the pandemic strongly enough. The Göttingen simulation also shows: To get the coronavirus pandemic under control, we have to keep social contacts to a minimum for another two weeks.

Number of new corona infections (as of 7 April 2020): The simulation of new infections (green dotted line) with Sars-CoV-2 by the Göttingen team shows the actual numbers (blue diamonds) quite accurately to date. This allows the prediction that the number of new infections will decrease continuously from now on (green line) thanks to the contact ban of 22 March. The researchers have also simulated how the number of new infections would have developed if there had been no restrictions in social life at all (grey line) and if the measures around 8 March (red line) and the additional measures around 16 March (orange line) had been maintained. In both cases the number of new infections would have continued to increase, even if it had temporarily decreased in the second case - Covid-19 would have spread exponentially thereafter.

It is an encouraging development, but not yet the all-clear. The number of coronavirus infections in Germany has been growing much more slowly since last weekend. “We are seeing a clear effect of the partial lock-down introduced on March 22, and of course, of the contributions of each individual,“ says Viola Priesemann, who heads a research group at the Max Planck Institute for Dynamics and Self-Organization in Göttingen.“As a society, we can be truly proud that we have achieved this turnaround.“

The team has been simulating the course of the corona epidemic in Germany together with scientists from the Göttingen Campus since mid-March. The model calculations not only make it possible to estimate the effects of the restrictions in public life on 8, 16 and 22 March. According to the model, the measures now in place will cause the number of new cases of Covid-19 to fall further in the next two weeks, apart from statistical fluctuations. As a result, the increase in confirmed infections would be significantly less pronounced, so that those seriously ill with Covid-19 would be able to receive the possible care in Germany. This would perhaps have been more difficult in another scenario: “Our model calculation also shows that we would now have around 200,000 confirmed infections if the mild restrictions of 8 March had remained in place, for example, not to mention if there had been no measures at all,“ says Viola Prieseman

According to the model calculations, the number of cases should be so low in about ten days that home confinement measures could be relaxed

The effective rate of propagation corresponds to the daily growth rate of new infections. It determines how high the case numbers might be about two weeks later after the test results are available The model also takes into account that recovered individuals are initially immune and can no longer contribute to the spread of the infection. “Even with the restrictions imposed around 8 March, which included football matches without fans, and the additional measures taken around 16 March, such as the closure of schools, kindergartens and many shops reduced the propagation rate significantly”, says Michael Wilczek, co-author of the study. “But not yet to zero or below. The dreaded exponential spread of the corona virus had therefore not yet been reduced.”

Number of confirmed corona infections (as of 7 April 2020): The current Göttingen model calculation shows quite accurately (reported number - blue diamonds; simulation - green dotted line) how many people in Germany have been proven to be infected with the corona virus by 7 April, so that the further development of infection numbers can also be predicted. According to this, the spread of the virus is likely to slow down considerably as a result of the contact ban of 22 March (green line). If there had been no restrictions at all (grey line) or if the measures around 8 March (red line) and the additional measures around 16 March (orange line) had remained in place, Covid-19 would have spread exponentially, according to the simulation.

However, in order to allow the contact ban to be relaxed in a few weeks' time, life in Germany must continue to run on emergency mode for the time being. The insight that can be derived from the Göttingen model calculation is obvious, if sobering: “If the restrictions are lifted, we could again run into exponential growth”, says Priesemann. “The number of confirmed cases in two weeks clearly depends on our behaviour today.”

But this also means that if we continue to follow the rules very carefully over the next two weeks, in the best of scenarios there could soon be only a few hundred new cases each days. With so few new infections, most contacts of each patient could identified and isolated. “I find it very encouraging that with stringent restrictions in the next ten days, we could push back the new infections to such an extent that, with caution, we could carry on – and hopefully with significantly fewer restrictions”, says Priesemann

The forecasts are constantly updated

In order to make the measures against the Corona pandemic as effective as possible, it would, of course, be helpful for policy makers to know the effect of individual restrictions. For example, it would be helpful if they knew whether the closure of schools and kindergartens, the restriction of trade, or the ban on private encounters was particularly effective in containing the epidemic. But even the Göttingen model calculation cannot clarify this.“It is difficult enough to estimate the effects of the entire set of measures – let alone the individual measures”, says Priesemann. Although the actual development of infection rates shows whether the assumptions of her team were correct, albeit with some delay, such a reality check for the estimated effects of individual measures is not yet possible.Irrespective of this, Priesemann’s research team is continually monitoring the predictions of the model. “For the past few weeks, my team has been working around the clock to develop the model. We are now able to add a new data point every day and see how the inference becomes more and more precise”, she says.

The Göttingen researchers not only make their data and results available on the Internet, but also make their model available to colleagues worldwide so they can simulate the development of the epidemic for other countries or for individual regions such as Germany. “We have had a few very exhausting weeks. But we are quite pleased that our research work can contribute to a greater understanding of the spread and containment of the corona epidemic in Germany”. 

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