Misc 03/04/2020

The curve is starting to get flatter

Mathematical models indicate that the number of new cases might fall next week

Toni Pou
3 min
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It looks as if the curve is getting flatter. That is the conclusion reached by the researchers who monitor the COVID-19 pandemic on a daily basis using mathematical models. Daniel López, a researcher with the computational biology and complex systems group at Universitat Politècnica de Catalunya has confirmed that “some days we get more cases and other days we get fewer, but the rise is not nearly as sharp as it was some days ago”. “We’re doing a good job”, says Àlex Arenas, the director of the research group in complex systems algorithms at Universitat Rovira i Virgili (URV). This trend is apparent in the number of new cases in Catalonia and Spain, as well as in the progression of the transmission rate, the average number of newly infected people from a single case. In early March the rate in Catalonia hovered at around 2 and then shot up, only to decrease gently down to the current level, which is nearly 1. Once the rate drops below 1 an epidemic is considered to be in check because —in principle— the number of infected individuals isn’t growing anymore. However, reality is not as perfect as the ideal mathematical curve, where the rate rises until it peaks and then proceeds to fall at the same pace.

Daniel López explains that it is “more fitting to talk about a sawtooth than a peak” and “that’s where we probably are in Catalonia at the moment”. The researcher believes that “round about April 23 we should be seeing a lower number of daily new cases than we have today”. The UPC group has developed a model based on the data gathered about the epidemic rather than on its working mechanism, which indicates that in Catalonia, Madrid and Spain as a whole the communication rate is fast approaching 1. The URV researchers’ model is based on the epidemic’s working mechanism, but also yields a communication rate of nearly 1 and, according to Àlex Arenas, they expect that “this rate to drop below 1 by next week”. The researcher explains that “next week we should see that the number of new cases levels off and even dips down”.

A slow return to normality

Nevertheless, scientists agree that it will be a slow journey back to normality. “The looming threat of a fresh outbreak will always be there because only a small part of the population has been infected by the virus”, López warns. “This is not the time to point fingers, but to stop making mistakes because the number of cases could rise again”, says Arenas. Furthermore, the data from China suggests that the drop in the number of new cases is more gradual that the rise, especially in densely-populated regions.

According to López, the priorities for next week should be “to ensure that the public health system stays in good shape, unlike now, when the situation is untenable” and when the time is right “to ease off the lockdown with a great deal of discipline”. Arenas believes that “much testing will be required to keep the disease in check” during the new phase. In order to prevent new outbreaks, the URV researchers also notes that “we will likely need a few additional weeks of seclusion following the total lockdown”. At the moment researchers are studying how we should go about progressively restoring mobility whilst avoiding new outbreaks.