Country-specific Optimization Strategy for Testing Through Contact Tracing Can Help Maintain a Low Reproduction Number (R_0) During Unlock
Abstract In response to the COVID19 pandemics, many countries have implemented lockdowns in multiple phases to ensure social distancing and quarantining of the infected subjects as a first step to contain the infection spread. Subsequent unlocks to reopen the economies started next waves and imposed extra burden on quarantine to keep the reproduction number ( R0<1 ). Even with initial strict lockdowns and recent launching of vaccination programs, many countries are still struggling to contain the infection which suggests that revisiting the mechanism of lockdown-unlock implementation and simultaneous underpinning of the potential sources diluting the effort of such lockdowns could help better contain the spread of infection. Here, building epidemic models and analyzing the metadata of 50 countries, we first found that the estimated values of R0, adjusted w.r.t the distribution of medical facilities and virus clades, correlates strongly with the testing rates across countries. However, testing capacity of a country is limited by its medical resources, hence, as we demonstrate, optimizing a cost-benefit trade-off between testing rate and unlocking extents implemented in a country specific manner can help in devising the strategies of unlocking the economy. Our study delineates a strategy to optimize this trade-off by utilizing country specific infection spread parameters estimated in the epidemic models and implementing them in a stochastic agent based contact tracing models. The analysis provides a quantitative estimate of testing rates required to maintain a low for different extents of unlock. We further found that a small fraction of superspreaders can drastically increase the number of infected individuals even during lockdowns, primarily due to a switch-like response stemming from the implicit systems-level positive feedback loop driving the spread of infection. Our model suggests that with a country specific optimal combination of unlock extents and testing rates, R0 <1 can be stabilized during a pandemic like COVID19. To harness the benefit of improved testing rates and minimize the infection spread, strict social distancing norms to restrict the movement of superspreaders is necessary, such that onset of the positive feedback loop mediated exponential infection spread can be avoided.