A modelling study highlights the power of detecting and isolating asymptomatic or very mildly affected individuals for COVID-19 epidemic management

Abstract

Background Mathematical modelling of infectious diseases is a powerful tool for the design of management policies and a fundamental part of the arsenal currently deployed to deal with the COVID-19 pandemic. Methods We present a compartmental model for the disease where symptomatic and asymptomatic individuals move separately. We introduced healthcare burden parameters allowing to infer possible containment and suppression strategies. In addition, the model was scaled up to describe different interconnected areas, giving the possibility to trigger regionalized measures. It was specially adjusted to Mendoza-Argentina’s parameters, but is easily adaptable for elsewhere. Results Overall, the simulations we carried out were notably more effective when mitigation measures were not relaxed in between the suppressive actions. Since asymptomatics or very mildly affected patients are the vast majority, we studied the impact of detecting and isolating them. The removal of asymptomatics from the infectious pool remarkably lowered the effective reproduction number, healthcare burden and overall fatality. Furthermore, different suppression triggers regarding ICU occupancy were attempted. The best scenario was found to be the combination of ICU occupancy triggers (on: 50%, off: 30%) with the detection and isolation of asymptomatic individuals. In the ideal assumption that 45% of the asymptomatics could be detected and isolated, there would be no need for complete lockdown, and Mendoza’s healthcare system would not collapse. Conclusions Our model and its analysis inform that the detection and isolation of all infected individuals, without leaving aside the asymptomatic group is the key to surpass this pandemic.

Modeling robust COVID-19 intensive care unit occupancy thresholds for imposing mitigation to prevent exceeding capacities

“…During Chicago's October 2020 epidemic wave, mitigation was implemented on November 20[31] when the COVID-19 ICU occupancy was 53% (S1Fig 16). However, Rt had already begin to decrease prior to implementation of official mitigation measures as individual action preceded government policy (S1Fig 17).Our suggested threshold of 60% for Chicago aligns with thresholds used in a modeling study that simulated multiple on-off cycles based on a fixed 50% ICU occupancy threshold[26]. Another modeling study evaluated an ICU threshold system that defined 30% occupancy as moderate risk, 30-60% occupancy as higher risk, and above 60% as very high risk[18].…”

“…Our suggested threshold of 60% for Chicago aligns with thresholds used in a modeling study that simulated multiple on-off cycles based on a fixed 50% ICU occupancy threshold [26]. Another modeling study evaluated an ICU threshold system that defined 30% occupancy as moderate risk, 30-60% occupancy as higher risk, and above 60% as very high risk [18].…”

“…Thresholds for action (ICU occupancy levels that, when met, trigger more intense mitigation measures against transmission) should not be arbitrarily selected but rather be designed to meet COVID-19-related public health targets. Several modelling studies explored short-term forecasting of ICU occupancies [17][18][19][20][21][22][23][24][25] and mitigation strategies in relation to ICU capacities [17][18][19]26]. However, the criteria for selection of thresholds for action has not been assessed in greater detail.…”

Role of asymptomatic and pre-symptomatic infections in covid-19 pandemic

“…One model estimated that transmission from asymptomatic individuals accounts for over half of all covid-19 transmissions, after considering scenarios with multiple covid-19 infectious periods and varying rates of transmission from those who never displayed symptoms 15. Several prediction models have indicated that the identification and isolation of all infected individuals, including those who are asymptomatic, is important for controlling the spread of covid-19 161718. In a worst scenario of unmitigated growth, researchers estimated that testing asymptomatic people may identify the virus five to eight days earlier than it would be detected in symptomatic people, a significant difference.…”

Mental health of individuals infected with SARS-CoV-2 during mandated isolation and compliance with recommendations—A population-based cohort study

“…Isolation is an indispensable measure to contain the SARS-CoV-2 virus and affects millions of people worldwide [ 1 , 2 ]. However, isolation, even if short-term, may also have a negative impact.…”