Fig. 1. The cycles of SARS-CoV-2 and COVID-19 vs. those of the alternating quarantine strategy.

a We collected data on the transitions between the SARS-CoV-2 and COVID-19 states and constructed the characteristic disease cycle. Upon exposure (E) individuals enter an average 5 day incubation period prior to developing symptoms—mild (I_M at a rate of 55%), severe (I_S, 10%), or critical (I_C, 5%). The remaining  ~30% are asymptomatic (AS). Infectiousness begins typically 3 days after exposure for symptomatic carriers, and 4 days for the asymptomatic (AS). The infection window (violet) captures the invisible presymptomatic (PS) spreading phase, in which individuals are infectious, but lack symptoms. Upon the onset of symptoms, infected individuals are isolated and cease to infect others. Consequently, asymptomatic individuals have a longer infection window, which extends until their transition to R. As the disease progresses a fraction of the infected population may require hospitalization (H) or ventilation (V), leading, to some probability of mortality (D). b The compartments of the COVID-19 cycle. We denote by I(t) the unity of all symptomatic individuals (I = I_M + I_S + I_C). This corresponds to the diagnosed case count in each country (Fig. 3), which covers mainly the patients who exhibit symptoms. c While the illustrated cycle in (a) captures the average transition times between all states, in reality, some level of variability exists across the population. This is captured by the distribution $P_i\left(t^{\prime }\right)$. For example, the individual transition time from E to PS, whose average is 3 days, is extracted from $P_1\left(t^{\prime }\right)$ (purple). d Alternating quarantine (AQ) splits the population into separate cohorts that alternate between periods of activity (going to work, blue) and inactivity (staying at home, red). Following their active week, (week 1) individuals in Cohort 1 may become exposed (yellow), in which case they will sit out their suspected pre-symptomatic period at home (week 2). By the end of their quarantine week, they will likely develop symptoms (orange) and remain in isolation until their full recovery. Those who did not develop symptoms during their week of quarantine are most likely uninfected (blue) and can resume activity in their upcoming active shift (week 3). Therefore the AQ cycle behaves as an effective ratchet, consistently quarantining the invisible spreaders, and hence, removing, with each weekly succession, infectious individuals from the active population.