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Predicting the Effectiveness of Population Replacement Strategy Using Mathematical Modeling
Published on: July 4, 2007
Mathematical model describing CoViD-19 in São Paulo, Brazil - evaluating isolation as control mechanism and
H M Yang1, L P Lombardi Junior1, F F M Castro2
1Department of Applied Mathematics, State University of Campinas, General Hospital of the Medicine School of University of São Paulo, Campinas, Brazil.
Insights
Mathematical modeling of COVID-19 in São Paulo suggests that delaying the release of isolated individuals, particularly the elderly, is crucial. Higher isolation rates could have prevented healthcare system collapse.
Area of Science:
- Epidemiology
- Mathematical Modeling
- Public Health
Background:
- The first COVID-19 case in São Paulo was confirmed on February 26, 2020, with the first death on March 16.
- São Paulo implemented non-essential activity isolation on March 24, 2020.
- Understanding the dynamics of coronavirus disease 2019 (CoViD-19) spread is critical for public health interventions.
Purpose of the Study:
- To develop a mathematical model simulating COVID-19 spread in São Paulo, considering age-stratified subpopulations.
- To estimate the basic reproduction number (R0) and assess the effectiveness of implemented isolation measures.
- To evaluate different release strategies for isolated populations and their impact on healthcare system burden.
Main Methods:
- Formulation of a deterministic mathematical model using non-linear ordinary differential equations.
- Inclusion of two subpopulations: young (≤60 years) and elder (>60 years).
- Parameter estimation using São Paulo's epidemiological data to simulate COVID-19 dissemination.
Main Results:
- The estimated basic reproduction number (R0) was 6.8.
- The model estimated that 50% of São Paulo's population was in isolation.
- Achieving 80% isolation could have prevented healthcare system collapse; however, all release strategies studied did not substantially reduce severe COVID-19 hospitalizations.
Conclusions:
- The initial isolation strategy in São Paulo was only partially successful in controlling the epidemic.
- Releasing young individuals while keeping the elderly isolated longer showed better outcomes among release strategies.
- Postponing the start of releasing isolated individuals is the recommended strategy to mitigate severe COVID-19 hospitalizations.
Abstract:
In São Paulo, Brazil, the first case of coronavirus disease 2019 (CoViD-19) was confirmed on 26 February, the first death due to CoViD-19 was registered on 16 March, and on 24 March, São Paulo implemented the isolation of persons in non-essential activities. A mathematical model was formulated based on non-linear ordinary differential equations considering young (60 years old or less) and elder (60 years old or more) subpopulations, aiming to describe the introduction and dissemination of the new coronavirus in São Paulo. This deterministic model used the data collected from São Paulo to estimate the model parameters, obtaining R0 = 6.8 for the basic reproduction number. The model also allowed to estimate that 50% of the population of São Paulo was in isolation, which permitted to describe the current epidemiological status. The goal of isolation implemented in São Paulo to control the rapid increase of the new coronavirus epidemic was partially succeeded, concluding that if isolation of at least 80% of the population had been implemented, the collapse in the health care system could be avoided. Nevertheless, the isolated persons must be released one day. Based on this model, we studied the potential epidemiological scenarios of release by varying the proportions of the release of young and elder persons. We also evaluated three different strategies of release: All isolated persons are released simultaneously, two and three releases divided in equal proportions. The better scenarios occurred when young persons are released, but maintaining elder persons isolated for a while. When compared with the epidemic without isolation, all strategies of release did not attain the goal of reducing substantially the number of hospitalisations due to severe CoViD-19. Hence, we concluded that the best decision must be postponing the beginning of the release.
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