Article Contents
Article Contents

# Systems theory and analysis of the implementation of non pharmaceutical policies for the mitigation of the COVID-19 pandemic

• * Corresponding author: Costas Poulios
• We utilize systems theory in the study of the implementation of non pharmaceutical strategies for the mitigation of the COVID-19 pandemic. We present two models. The first one is a model of predictive control with receding horizon and discontinuous actions of unknown costs for the implementation of adaptive triggering policies during the disease. This model is based on a periodic assessment of the peak of the pandemic (and, thus, of the health care demand) utilizing the latest data about the transmission and recovery rate of the disease. Consequently, the model seems to be suitable for discontinuous, non-mechanical (i.e. human) actions with unknown effectiveness, like those applied in the case of COVID-19. Secondly, we consider a feedback control problem in order to contain the pandemic at the capacity of the NHS (National Health System). As input parameter we consider the value $p$ that reflects the intensity-effectiveness of the measures applied and as output the predicted maximum of infected people to be treated by NHS. The feedback control regulates $p$ so that the number of infected people is manageable. Based on this approach, we address the following questions: (a) the limits of improvement of this approach; (b) the effectiveness of this approach; (c) the time horizon and timing of the application.

Mathematics Subject Classification: Primary: 93B52, 93C40, 92D30.

 Citation:

• Figure 1.  Visualization of the SIR model with random $\beta$ and $\gamma$ in time $t$. As initial values, S(0) = 999, I(0) = 1 and R(0) = 0 were chosen

Figure 2.  Mitigation strategy scenarios for UK showing critical care bed requirements. Source: Ferguson et al. (2020)

Figure 3.  Feedback control for the implementation of social distancing policies

Figure 4.  The evolution of the number $I(t)$ of infected people in the case where no mitigation measures are applied

Figure 5.  The evolution of the number $I(t)$ of infected people (on the left) and of the parameter $p$ (on the right) in the case where a feedback control scenario with $\lambda = 0.0025$ is applied

Figure 6.  The evolution of the number $I(t)$ of infected people (on the left) and of the parameter $p$ (on the right) in the case where a feedback control scenario $\lambda = 0.002$ is applied

Figure 7.  The evolution of the number $I(t)$ of infected people (on the left) and of the parameter $p$ (on the right) in the case where a feedback control scenario $\lambda = 0.002$ is applied with a delay of $T = 2$ unit times

Figure 8.  According to WHO there are 4, 761, 559 confirmed cases. Source: WHO (2020) [17]

Figure 9.  According to John Hopkins University there are 4, 927, 487 confirmed cases. Source:John Hopkins University (2020) [19]

Figure 10.  According to Harvard and the Children hospital there are 9, 474, 948 confirmed cases. Source: Harvard (2020) [18]

Figure 11.  Daily evolution of $b$ for 21 countries starting the 22/1/2020 and finishes the 8/5/2020

Figure 12.  Estimation of progress for the average $\beta(t)$ in time $t$. The black dots are the average values of $\beta$ and the red line is the polynomial best fit line

Figure 13.  Daily evolution of the average $I_{\max}$ and the $I(t)$ from 4 countries as an indicative trend, starting the 22/1/2020 and finishes the 8/5/2020. The blue line represent the $I(t)$ and the red the $I_{\max}$

Table 1.  Summary of NPI interventions considered

 Label Policy Description CI Case isolation in the home Symptomatic cases stay at home for 7 days, reducing non-household contacts by 75% for this period. Household contacts remain unchanged. Assume 70% of household comply with the policy. HQ Voluntary home quarantine Following identification of a symptomatic case in the household, all household members remain at home for 14 days. Household contact rates double during this quarantine period, contacts in the community reduce by 75%. Assume 50% of household comply with the policy. SDO Social distancing of those over 70 years of age Reduce contacts by 50% in workplaces, increase household contacts by 25% and reduce other contacts by 75%. Assume 75% compliance with policy. SD Social distancing of entire population All households reduce contact outside household, school or workplace by 75%. School contact rates unchanged, workplace contact rates reduced by 25%. Household contact rates assumed to increase by 25%. PC Closure of schools and universities Closure of all schools, 25% of universities remain open. Household contact rates for student families increase by 50% during closure. Contacts in the community increase by 25% during closure.

Table 2.  Sample of twenty-one countries from the 267 countries and big cities. For China the city of Beijing was chosen. The $b$ parameter was estimated by using Equation (18)

 COUNTRY $b$ parameter SWISS 0.257158556 BRAZIL 0.233817403 ITALY 0.203539698 NORWAY 0.197869991 SPAIN 0.19306215 EGYPT 0.19012821 USA 0.189437334 PAKISTAN 0.184307553 BELGIUM 0.178032037 ETHIOPIA 0.167117704 RUSSIA 0.160845659 FRANCE 0.153958202 UK 0.153852808 GERMANY 0.153678417 SOUTH KOREA 0.148665135 SWEDEN 0.141608744 BULGARIA 0.141558434 CYPRUS 0.132396806 GREECE 0.120185025 ALBANIA 0.109905162 CHINA 0.053298278
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