April 10, 2021

The alternation of confinements: a measure that flattens the curve to 80%

A woman with a mask looks out a window.

A woman with a mask looks out a window.

Researchers at Israel’s Bar-Ilan University have developed a strategy based on alternating confinements: first the population is divided into two groups and then these groups alternate between confinement and routine activity in weekly succession. Along with isolating symptomatic spreaders, this strategy can help defeat the virus, while maintaining socioeconomic activity at a 50 percent level, as published in the journal Nature Communications.

The social distancing, from mobility restrictions to complete lockdowns, can last for many weeks, possibly even months, a potentially devastating result for social and economic stability.

One of the challenges is that patients cannot be selectively isolated, since many of the propagators remain presymptomatic for a period ranging from several days to up to two weeks: invisible propagators that remain socially active. Therefore, it appears that without confinement of the entire population, it is not possible to effectively isolate carriers.

In this new alternative containment strategy, society is divided into two groups, with little interaction between them: one half active this week and the other only the next. This already slows the spread, but its main advantage is that it helps isolate invisible propagators, such as presymptomatic carriers that are still in the incubation period.

“Let’s consider an individual who became infected during their active week. They are now in their presymptomatic period, the most dangerous stage, where they are invisible propagators. The crucial point is that, according to this alternative confinement, they are now programmed to enter in its confinement phase. If they stay at home for an additional week, they will most likely begin to have symptoms and therefore remain isolated until they fully recover. In fact, if after a week of confinement they do not show symptoms, it is most likely that they are not infected and can participate in social and professional activities during their active week. Therefore, alternating confinement with total isolation of symptomatic propagators ensures that, at all times, the majority of invisible propagators are inactive, as their incubation period is naturally directed towards their confinement phase, “the authors explain. .

Those responsible for the work start from the premise that “most people are extremely cautious and refrain from any contact with someone showing symptoms“.” Therefore, we believe that it is the invisible propagators that are the main contributors to the proliferation of cases. Our strategy addresses precisely this challenge: putting each person in weekly isolation after they have been potentially exposed during their active week. In this way, we effectively isolate not only the sick, but also the majority of presymptomatic carriers, “they say.

This research team simulated the spread of COVID-19 using a detailed epidemiological model. This model tracks the number of individuals in their transition between the different stages of the disease, from the presymptomatic phase to the appearance of symptoms and, throughout the disease cycle, to possible hospitalization, ventilation or even mortality . They found that employing their strategy significantly reduces the spread and helps flatten the curve., with an efficiency comparable to that of a confinement of 80 percent, all this while maintaining a continuous socio-economic activity at 50 percent of its capacity.

“We can achieve more if we also adopt responsible behavior. Specifically, we hope that even during their busy week, people will continue to interact with caution: avoid physical contact, increase personal space and practice hygienic behavior. These additional measures, together to our alternative containment strategy, they can help inhibit the spread, allowing us to overcome COVID-19 with reasonable economic consequences, “they highlight.


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