Why lockdown? Simplified arithmetic tools for decision-makers, health professionals, journalists and the general public to explore containment options for the novel coronavirus

Abstract

Half the world's population is already under lock-down and the remainder will have to follow if the ongoing novel coronavirus 2019 virus pandemic is to be contained. Faced with such brutally difficult decisions, it is essential that as many people as possible understand (1) why lockdown interventions represent the only realistic way for individual countries to contain their nationallevel epidemics before they turn into public health catastrophes, (2) why these need to be implemented so early, so aggressively and for such extended periods, and (3) why international cooperation to conditionally re-open trade and travel between countries that have successfully eliminated local transmission represents the only way to contain the pandemic at global level. Here we present simplified arithmetic models of COVID-19 transmission, control and elimination in userfriendly Shiny and Excel formats that allow non-specialists to explore, query, critique and understand the containment decisions facing their country and the world at large. Based on parameter values representative of the United Republic of Tanzania, which is still early enough in its epidemic cycle and response to avert a national catastrophe, national containment and elimination with less than 10 deaths is predicted for highly rigorous lock down within 5 weeks of the first confirmed cases and maintained for 15 weeks. However, elimination may only be sustained if case importation from outside the country is comprehensively contained by isolating for three weeks all incoming travellers, except those from countries certified as COVID-free in the future. Any substantive relaxation of these assumptions, specifically shortening the lock-down period, less rigorous lockdown or imperfect importation containment, may facilitate epidemic re-initiation, resulting in over half a million deaths unless rigorously contained a second time. Removing contact tracing and isolation has minimal impact on successful containment trajectories because high incidence of similar mild symptoms caused by other common pathogens attenuates detection success of COVID-19 testing. Nevertheless, contact tracing is recommended as an invaluable epidemiological surveillance platform for monitoring and characterizing the epidemic, and for understanding the influence of interventions on transmission dynamics.

Containment strategies for the 2019 Novel Coronavirus: flatten the curve or crush it?

“…Unfortunately, and consistent with the way their work was represented in one of our national newspapers, the authors only emphasize one side of their own results in the abstract of their paper. There are two issues the authors fail to mention in their own summary: (1) at the end of the 18 month period they presented (Figure 1), epidemics suppressed sufficiently for ICUs to consistently cope with are still going strong, requiring just as much effort to keep contained and continuing to cause illness, death and socioeconomic disruption, (2) when they simulated crush the curve [3] approaches to eliminating the virus with sustained and uninterrupted restrictions, their timelines to that exit point are about 3 months ( Figure 2), very similar to our own predictions [2,4].…”

“…Coverage in a national newspaper here in Ireland prompted me to read through the recent epidemiological modelling paper in the European Journal of Epidemiology by Dr. Chowdhury and his colleagues in the Global Dynamic Interventions Strategies for COVID-19 Collaborative Group [1]. The modelling approaches taken look solid and reasonable to me, and indeed several of the numerical predictions match our own projections [2]. Worryingly, these similarities including a mean fatality rate of about 1% of the overall population, even in high income countries, in the event of a full-blown, uncontained epidemic.…”

“…So why not just put our foot on the accelerator to terminate the epidemic in time for the coming winter [2][3][4]? The second set of graphs in figure 2 of Chowdhury et al [1] almost exactly matches our own [2,4] and confirms that elimination timelines of 2-4 months are feasible. In the authors' own words: "…in 3 months, most of the countries would not have any new cases to report".…”

A simple arithmetic rationale for crushing the epidemic curve of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) instead of flattening it

“…Here is presented a simple arithmetic rationale for why preferable crush the curve strategies, to eliminate transmission within months, would require only a modest amount of additional containment effort when compared to flatten the curve strategies that allow epidemics to persist at a steady, supposedly manageable level for years, decades or even indefinitely. 2,9 Much can be learned by simply examining the targets for the two alternative strategies, relative to the starting point, expressed in terms of the reproductive number of the virus (R) or number of new infections arising from any initial infection over its full duration. An epidemic curve which has been exactly flattened, so that the rate of incidence of new infections remains constant (R0=1.0), represents a tipping point in the struggle to contain SARS-CoV-2.…”

A Metapopulation Network Model for the Spreading of SARS-CoV-2: Case Study for Ireland⋆

“…As a simple measure, we define some threshold I th as the maximum number of infected that can be present before we go back into lock-down and go through earlier phases again. Such a procedure corresponds to dynamic [21][22][23] or active [24] interventions. Specifically, we simulate until phase 3 as before to maintain the agreement with reported cases.…”