A team of researchers has revealed a pioneering model that aims to predict the rate of propagation of Covid-19 in each country in Europe.
It was battle stations on September 24 when Brussels demanded European countries immediately tighten their control measures in the face of the spread of Covid-19, in order to avoid a second wave of the pandemic. The European Centre for Disease Control and Prevention singled out 13 European countries with alarmingly rising rates of infection, including France and Britain.
Although the race against a second wave of Covid-19 is well underway on the continent, a team of scientists has set about modelling the future trajectory of the virus's spread in Europe. Their simulations, published on September 23 in the scientific journal Nature, predict that all European countries will have reached the peak of the second wave of the pandemic by January 2021 at the latest.
Model borrowed from particle physics
France may not have long to wait as the next peak is predicted for the beginning of October. In the United Kingdom, the number of new infections looks set to continue to rise until mid-November. Poland and Sweden, two countries relying on herd immunity to fight the virus, are expected to keep rising until the beginning of next year.
To achieve these predictions, a team of scientists, led by French National Centre for Scientific Research physicist Giacomo Cacciapaglia, has adopted an innovative approach to simulate the temporal evolution of the epidemic: particle physics. Researchers have applied an equation typically used to predict the interactions between tiny physical elements to the trajectory of the coronavirus.
"We found that by applying this model, we obtained a result that was consistent with what happened during the first wave and we wanted to test it to try to anticipate what might happen," says Cacciapaglia, speaking with FRANCE 24.
The advantage of this method lies in its simplicity. Compared to mathematical models traditionally used in epidemiology, "there are far fewer parameters that need to be included in the equation in order to carry out the simulations", explains Cacciapaglia.
In this case, the researchers only took into account the total number of Covid-19 infections in each country and also any movements within a territory and between European States from March to July 2020. There was no need to take into account factors such as levels of social distancing, the average number of people per household or other criteria that are required in other models.
It is this simplicity that made it possible to construct projections at a wider European level. "The more parameters we integrate, the more variations are possible in each territory and this is what can make large-scale modelling difficult," says Cacciapaglia.
Virus spreading faster in France than expected
The other side of the coin is that this model, because of its simplicity, only allows "one aspect of the epidemic to be controlled, that is the speed of spread of the virus", Cacciapaglia points out. It gives no indication of the scale of the epidemic, as in the precise number of cases, or the mortality rate.
It was also necessary for scientists to assume that the same protective measures used during the first wave, such as social distancing, limits on the number of people allowed to gather, quarantines, lockdowns, would also be applied to contain this second wave.
Despite the apparent simplicity of this, it has already begun to demonstrate its relevance. The team's projections, which began in June, proved to be "broadly in line" with the reality of the virus’s progress in Europe over the summer months.
Some countries have so far fared even better than predicted. In Finland and Italy, for example, the virus seems, for the time being, to have gained less ground than expected. "One possible explanation is that the measures decided by the authorities [since this summer, editor's note] have been more effective than what was done during the first wave, and the population has also been more vigilant," says Cacciapaglia. In other cases, such as in France, "the virus is spreading slightly faster than according to our calculations", notes the researcher.
Initial observations confirm the importance of social distancing and border control measures in the fight against the spread of Covid-19.
For Cacciapaglia, this model could prove useful to anticipate future periods of high contamination or new waves. It is for this very reason that one hopes we don't have to pull this model out of the drawer too often.
This article has been translated from the original in French.