With strict infection control measures in place in most countries, the question is how long these measures will have to last. Will we have to live with contact restrictions and closed schools, universities and businesses for months? Two research teams examined this question using model simulations. Both come to a less edifying conclusion: as soon as the social distance is removed, the corona virus will gain ground again. A second, even worse wave of Covid 19 cases could then occur.
The Sars-CoV-2 coronavirus is still spreading. While the number of new infections in South Korea, China and Iran has now decreased significantly, the number of cases of Covid 19 in Europe and especially in the United States is still rising sharply. In order to avoid overloading health systems, most countries have now introduced strict infection control measures. This includes the 14-day quarantine of Covid sufferers and suspected cases, but also the ban on events, the closure of schools, universities, non-essential shops and restaurants. In addition, the principle of social distancing applies; in some countries and particularly affected areas, curfews have even been imposed. Epidemiologists agree that it is only with such drastic interventions in everyday life that the number of new infections can be reduced and the infection curve kept flat.
Contact blocking necessary for months
However, these measures against the pandemic have serious negative consequences for public life, society and the economy. The question therefore arises as to the duration of this state of emergency: How long must we remain in this “standstill” in order to contain the pandemic? And what happens when the strict measures are relaxed again? A team of researchers led by Neil Ferguson from Imperial College London recently provided a first clue using a model simulation. Using the example of Great Britain and the USA, they had examined how effective quarantine, school closures and social distance are, either only for the risk groups at risk or for the entire population. It was shown that quarantine and the social isolation of the pre-ill and the elderly reduce the number of seriously ill people in the intensive care units by around two thirds. However, this alone would not stop the further spread of the corona virus.
This will only succeed if the entire population avoids contact and the schools remain closed, as the researchers report. Then around three weeks after the start of the measures, the number of cases drops and the transmission rate – the so-called reproductive number – falls below 1. This means that each infected person infects less than one other person and the spread of the virus stops as a result. However, the model simulation unfortunately also showed that these strict measures must last at least three months – and that at least some of the measures must remain in place until a vaccine against Sars-CoV-2 is used. Because the number of cases is increasing again after loosening the widespread social distancing, this strict ban on contacts probably has to be introduced from time to time.
Explosive rise at the end of the measures
A research team led by Niki Popper from the Vienna University of Technology and their spin-off dwh Simulation Services comes to similar results. They have developed a complex model that depicts the population structure in Austria, the infection behavior of the corona virus and the typical extent of contact between people at work, at school and in other social situations. The population of the city of Vienna served as a real model for this scenario. “In the model, every real person is represented by a virtual image, that is, a digital twin,” the researchers explain. “The concept of the digital twin now gives the modeler
complete freedom to be different in this virtual Vienna
Evaluate (forecast) scenarios. ”The basic scenario shows the current state: schools, universities, many shops and around 25 percent of the workplaces are closed, and contact restrictions apply. This has reduced leisure contacts by around 50 percent.
The simulation showed that if these measures continue, the number of Covid cases will continue to decrease over the summer. A similar situation would occur if workplaces such as shops were reopened after Easter, but contact closings and school closings continued. The decline in the number of diseases would then be slower, but the health system would not reach its limit, as the researchers report. On the other hand, the consequences would be completely different if all measures were to be abolished after the initial successful decline in new infections: “It would be wrong to return to everyday life immediately,” emphasizes Popper. “If the number of contacts immediately rises to the level that used to be the case, the number of illnesses will increase again very quickly, similar to how a compressed sponge expands again when the pressure is removed.”
Second wave looms
The consequence of such premature and too extensive loosening would be a second corona wave, which could be even more serious than the current one, as the researchers warn. Such a second wave of outbreaks would threaten if the workplaces in Austria were reopened from Easter and the schools in Austria from May 4th. Even if the other contact restrictions remain in effect, this could lead to an increase in Covid cases that exceeds current levels. Popper and her team therefore recommend a kind of driving on sight: in the next few weeks and months, the measures could be gradually withdrawn and tightened again immediately if a new increase in the number of cases is announced. “Of course, long-term forecasts are always subject to a certain degree of uncertainty,” emphasizes Popper. “It is important to improve the models every week and to adapt them to the latest data. The more we learn about the spread of Covid-19, the more reliable our view of the future will be. “
Source: Imperial College London, doi: 10.25561 / 77482; technical University of Vienna