Critical community size for COVID-19 -- a model based approach to provide a rationale behind the lockdown

Abstract

Background Restrictive mass quarantine or lockdown has been implemented as the most important controlling measure to fight against COVID-19. Many countries have enforced 2 -4 weeks' lockdown and are extending the period depending on their current disease scenario. Most probably the 14-day period of estimated communicability of COVID-19 prompted such decision. But the idea that, if the susceptible population drops below certain threshold, the infection would naturally die out in small communities after a fixed time (following the outbreak), unless the disease is reintroduced from outside, was proposed by Bartlett in 1957. This threshold was termed as Critical Community Size (CCS). Methods We propose an SEIR model that explains COVID-19 disease dynamics. Using our model, we have calculated country-specific expected time to extinction (TTE) and CCS that would essentially determine the ideal number of lockdown days required and size of quarantined population. Findings With the given country-wise rates of death, recovery and other parameters, we 1

Global Experiences of Community Responses to COVID-19: A Systematic Literature Review

“…However, limited lockdown is more commonly used in developed countries rather than in developing ones. It can involve comprehensive biotechnology-based screening for suspected cases and thorough tracing of contacts based on adequate medical resources and a well-supported, community-based team of trained personnel, which are often not available in developing countries ( 92 , 93 ). Health system capabilities define possible boundaries for community prevention measures.…”

Unlinking super-linkers: the topology of epidemic response (Covid-19)

“…Application and containment: The ability to quickly identify infections via a comprehensive testing regime is a pre-requisite for a successful intervention via graph-based approaches including super-link isolation. Our technique can be seen as a sophisticated version of its fat-fingered cousin, the full social lockdown [14] -instead of disabling all proximity encounters, it is enough to disable a carefully selected fraction as part of a targeted intervention. It is likely that such a step would be more socially sustainable as opposed to a full social lockdown.…”

On an interval prediction of COVID-19 development based on a SEIR epidemic model

“…This method also uses the estimated values of E t (see (3) for the detailed description), but it does not use (approximated) derivatives. The idea of this approach is based on the observation that a straight line can approximate ln(E t ) (the variable E t is exponentially growing) for any constant values of p t−τ p and r t−τ r : ln(E t ) = at + b, for some a, b ∈ R. Such an approximation filters the noise contrarily to the derivativebased method presented in the previous subsection.…”

“…There exist many sorts and varieties of SEIR models [1] (e.g., in the most simplistic case, the classes E and I are modeled at once, leading to a SIR model). A specificity of COVID-19 pandemics is the global confinement imposed by most countries worldwide, influencing the virus dynamics [3]. In recent literature, numerous approaches propose how to reflect the confinement characteristics in the mathematical models [4,5,6].…”