Lacking a drug or a vaccine we are forced to battle COVID-19 by means of social distancing, from mobility restrictions to complete lockdowns. Most projections indicate that this may take many weeks, possibly even months, a potentially devastating outcome for social and economic stability. One of the challenges is that we cannot selectively isolate the sick, since many of the spreaders remain asymptomatic for a period ranging from several days to as much as two weeks - invisible spreaders that continue to be socially active. Hence, it seems that without a population wide lockdown we cannot effectively isolate the carriers. To bypass this we offer a strategy based on Alternating lockdowns: first we split the population into two groups, then these groups alternate between lockdown and routine activity in weekly succession. Together with isolation of the symptomatic spreaders and the adoption of everyday prophylactic behaviors this strategy can help us defeat the virus, while sustaining our socio-economic activity at a 50% level.
In the Alternating lockdown routine, society will be partitioned into two groups, with little interaction between them - one half active this week, and the other only active the next. This will already slow the spread, but its main advantage is that it helps isolate the invisible spreaders, i.e. the asymptomatic carriers who are still in the incubation period. To understand this consider an individual who became infected during their active week. By the end of that week they will enter their lockdown phase, then staying at home for another week, they will most likely begin to exhibit symptoms, and therefore remain in isolation until their full recovery. Indeed, if a person, following a week of lockdown, shows no symptoms, they are most likely uninfected and can partake in social and professional activities during their active week. Therefore, Alternating lockdown with full isolation of symptomatic spreaders ensures that at all times, the majority of invisible spreaders are inactive, as their incubation period is naturally directed towards their lockdown phase.
At present, most people are extremely cautious, and will refrain from any contact with someone showing symptoms. Therefore, we believe that it is the invisible spreaders that are the main contributors to the proliferating case count. Our strategy is precisely directed at this challenge - placing each person on weekly lockdown after they were potentially exposed during their active week. Hence, we effectively isolate not just the sick, but also the majority of the asymptomatic carriers.
To examine this we simulated the spread of COVID-19 using the SEIR model, assuming that only the invisible spreaders (E state) contribute to the infection. We find that employing our strategy significantly reduces the spread and helps flatten the curve. But we can achieve more if we also adopt responsible behavior. Specifically, we expect that even during their active week, people will continue to interact with caution: avoid physical contact, increase personal space and practice hygienic behavior. These additional measures, when coupled with our Alternating lockdown strategy can help inhibit the spread, allowing us to overcome COVID-19 with reasonable economic consequences.
Sustaining restrictive measures such as lockdowns is always a challenge, since some percentage of the population may not cooperate, especially in democratic and individualistic societies. We therefore, allowed, in our simulation for a fraction of defectors who continue to be active even during their lockdown phase. This can also represent exempt individuals, who hold essential positions and cannot be under lockdown. We find that even under 30% of non-cooperators we still overcome the viral spread.
The proposed weekly succession is aimed to sustain a functional economy in these challenging times. We believe that, providing an outlet for people to continue their social and professional activity, at least at 50% capacity, will, in and of itself encourage cooperation, as it relaxes some of the individual stress endured under lockdown.
Do we call for the immediate implementation of this policy? No. Not yet. However, we think this idea must be under consideration, and further examined against real-time data. We are happy to accept comments, critique, or help advise policy makers on implementing this solution.
Our detailed mathematical analysis and numerical results, including all our codes, will be soon published on the Arxive.