If we cannot resume economic activity without causing a resurgence of Covid-19 infections, we face a bleak and unpredictable future of opening and closing schools and businesses.
We can find a way out of this dilemma by exploiting a key property of the virus: its latency period – the time period of three days on average between when a person is infected and when he can infect others.
People can work in two-week cycles, at work for four days and then, by the time they can become infectious, 10 days at home locked out. The strategy works even better when the population is divided into two groups of households working alternately for weeks.
Austrian school authorities will adopt a simple version – with two groups of students attending school for five days every two weeks – from May 18.
The models we created at the Weizmann Institute in Israel predict that this two-week cycle can reduce the number of times the virus reproduces – the average number of people infected with each person infected – below one. A 10-4 cycle could therefore suppress the epidemic while allowing sustainable economic activity.
Even if a person is infected and without symptoms, they will only be in contact with people outside their home for four days every two weeks, not 10 days, as with a normal schedule. This strategy gives another punch: it reduces the density of people at work and at school, thereby reducing the transmission of the virus.
Schools could involve students for four consecutive days every two weeks, in two alternating groups, and use distance learning methods on other school days. Children would go to school on the same days that their parents go to work.
The companies would work almost continuously, alternating between two groups of workers, for a regular and predictable production. This would increase consumer confidence, simultaneously boosting supply and demand.
During lockout days, this approach only requires respecting the level of distancing already demonstrated in European countries and New York. It avoids the economic and psychological costs of opening up the economy and the need to restore full lockdown when cases inevitably re-emerge. Giving hope and then withdrawing it can cause despair and resistance.
A 10-4 routine provides at least part-time employment for millions of people who have been laid off or sent on leave without pay. These jobs prevent the devastating and often lasting, mental and physical effects of unemployment. For those living on money, there would be four days to make a living, reducing the economic need to ignore lockout. Business bankruptcies would also be reduced, accelerating a possible economic recovery.
The cyclical strategy is easy to explain and apply. It is fair to know who can return to work. It applies to any scale: a school, a business, a city, a state. A region using the cyclical strategy is protected: infections from outside cannot spread widely if the number of reproduction is less than one. It is also compatible with all other countermeasures under development.
Workers can and should always use masks and distances when at work. This proposal is not, however, based on large-scale tests, which are not yet available everywhere in the United States and may never be available in large parts of the world. It can be launched as soon as a regular drop in cases indicates that the lock has been effective.
The cyclical strategy should be part of an overall exit strategy, including self-quarantine of people with symptoms, contact tracing and isolation, and protection of at-risk groups. The cyclic strategy can be tested in limited regions for specific trial periods, even a month. If the infection rate increases, it can be adjusted to fewer working days. Conversely, if things go well, additional working days can be added. In some scenarios, only four or five lockdown days in each two-week cycle could still prevent a resurgence.