This section describes the results obtained in this study. Two results were obtained in this study, namely modeling results and numerical simulation results.
4.1. Modelling Result
In this study, a COVID-19 spread model is formed that considers the possibility of a transition in the severity of symptoms in infected patients, as well as the possibility of reinfection. The model formed has three compartments, namely susceptible (S), infected (I), and susceptible (S). The epidemiological mathematical model that has been created is used to model the COVID-19 pandemic in various scenarios.
In Equation (5), where
is the number of susceptible populations at time
and
is the number of infected populations at time
t. The schematic diagram of the spread of COVID-19 referred to in this study is presented in
Figure 2.
The explanation of
Figure 2 is as follows:
A person who is susceptible in period ; can be infected in the next period by COVID-19 into the infected group or remain susceptible
An infected person can have mild symptoms or severe symptoms For the patient is assumed not to require treatment at a health facility such as a hospital. Whereas for the patient is assumed to require medical treatment at a health facility.
Due to the limited capacity of health facilities, not all patients with severe symptoms of can receive treatment at health facilities. This results in a treated severe symptom group and an untreated severe symptom group .
Transitions in symptom severity may occur between
and
). Since
consists of
and
, symptom severity transitions are described in
Figure 3.
Based on this explanation and
Figure 3, it is known that compartment
is divided into three parts, namely:
Does not require treatment in a health facility (. It is assumed that in each time period, only a portion of the members of compartment require treatment so that the rest can self-isolate without needing to be treated in health facilities such as hospitals. For groups that are positive for COVID-19 but do not require intensive care in a hospital, the notation is used.
Needed treatment at a health facility but did not get it,
. It is assumed that there are health facilities in each area, but their capacity is limited, resulting in the possibility of patients who need treatment but cannot be treated because of this problem. For groups that are positive for COVID-19 and require intensive care but do not receive it, the notation
is used. Equation (12) describes
.
Hospitalized
This is a group that needs medical care and receives it.
is shown in Equation (13).
and at any time
, Equation (14) applies.
Next, the capacity constraint in health facilities is modeled. The number of beds for treating COVID-19 patients at the start of the pandemic
is shown in Equation (15).
where
is the fraction of COVID-19 treatment beds at the start of the pandemic, and
is the total number of hospital beds. Over time, the number of COVID-19 patients will increase, which presents a situation where the number of existing hospital capacities needs to be increased. At any time
, if the number of beds
is less than the number of
, then the bed capacity will be increased based on
. The existence of capacity constraints makes the addition of beds only possible for
fractions of
so the number of available bed capacities at time
is shown by Equation (16).
for each additional bed, it is assumed that the ratio between the number of beds with nurses and doctors remains the same, as in Equations (17) and (18).
where
is the number of nurses, and
is the number of doctors.
and
are the numbers of nurses and doctors in period 0 or at the beginning of the pandemic. Furthermore,
Figure 3 has previously shown the dynamics of COVID-19 with the number of patients requiring medical care. It is assumed that the patient’s chances of recovery and death depend on the severity of the symptoms and whether the patient receives treatment. This is shown by Equations (19) and (20).
where
is the probability of death, and
is the chance of recovery of the COVID-19 patient. After that, let
denote the probability that the patient will leave compartment
. The probability of this happening is if the patient recovers or dies. The
relations for
,
, and
are found in Equations (21)–(23).
Patients can experience changes in the severity of symptoms, and this keeps the patient in compartment
, but only the severity of the symptom changes. If
denotes the probability of transition, then the probability that no transition occurs or the patient leaves compartment
is given by Equation (24).
and this applies to
, and
, if Equation (24) is substituted with Equations (21)–(23), then Equations (25)–(27) are as follows,
The relationship between the transition probability
p and the probability of a patient exiting compartment I is depicted in
Figure 4.
Furthermore, due to possible transitions in symptom severity, patients infected with COVID-19 may have different treatment durations. Therefore,
needs to be considered from time to time, as in Equation (28).
Next, the number of patients who can no longer infect others corresponds to the number who died and recovered from COVID-19. Hence,
Now suppose
is the average number of people infected by one person per unit time
, and
is the number of people infected by an infectious person during the course of his infection. Thus, it becomes Equation (31).
Based on the explanation that has been made, the number of new infections each time
is given in Equation (32).
is always positive,
, where
is the type of government intervention, and
is the fraction of the infected population that is properly quarantined, so that for the compartments
formed, Equations (33)–(37) apply.
After modeling the spread of COVID-19 and the number of patients who need treatment, modeling is carried out regarding the cost of handling the COVID-19 pandemic. In this study, the cost of handling the COVID-19 pandemic considers three types of financing. The first type is the cost of care for patients who experience severe symptoms of
. Meanwhile, the second type is the cost of additional health facilities for patients with severe symptoms who are rejected on the grounds that the existing health facilities are full
. Then, the last is the cost of interventions carried out during the time span
. In this study, the cost of treating COVID-19 patient
is formulated in Equation (38),
where
is the cost of paying nurses,
is the cost of paying doctors, and
is the cost of administration and medicines needed to treat COVID-19 patients within 1 week. Meanwhile, the cost of adding health facilities
is formulated in Equation (39),
where
is the floor function,
is the cost of building a health facility,
is the cost of adding one new bed, and
is the number of COVID-19 treatment beds available at time
. Furthermore, the cost of intervention is calculated using Equation (40).
There are various interventions that can be conducted in one time interval. Interventions can also be carried out simultaneously between intervention 1, intervention 2, intervention 3, and so on. Thus, the cost of intervention is calculated using Equation (40). Based on Equations (38)–(40), the total cost of handling COVID-19 patient
needs to be prepared in Equation (41),
4.2. Parameter Estimation Results
In this study, the parameters used were estimated using real data to provide simulation results closest to the actual phenomena in the field. There are 11 parameters used in this study. Ten are estimated parameters, and one is assumed because no data are available. In this study, the assumed parameter is parameter n, which is the bed fraction that can be added within the next week. In this study, we used the value of
. We use this value by considering the time interval used; one week is a short time, meaning that even though the government has funds, there is still a time limit that can limit the number of beds that can be added. Furthermore, for other estimated parameters, we use real data related to the definition of these parameters. All parameter estimation results in this study are summarized in
Table 1.
Parameter
is estimated using data on the number of West Java hospital beds in 2019.
The
parameter was estimated using daily COVID-19 mortality data. The parameters are calibrated from the parameters using deaths that occurred during quarantine.
The parameter was estimated using daily COVID-19 recovery data. For parameters , was calibrated from parameter using cures that occurred during quarantine.
Parameter is estimated using parameters and using Equations (21)–(23).
Parameter is estimated using parameter and Equations (25)–(27).
The parameters reported in
Table 1 are then employed in this work for numerical simulations of the COVID-19 spread model. The parameter estimation findings are validated before being utilized in numerical simulations, assessing the model’s correctness against the data used. The validation process ensures that the model accurately reflects real-world scenarios and can provide reliable predictions for the spread of COVID-19. This rigorous approach enhances the credibility and usefulness of the simulation results in guiding public health interventions and decision-making. This is accomplished graphically by showing a simulation of the model created using the parameters listed in
Table 1.
Figure 5 and
Figure 6 depict a plot of model predictions versus data from COVID-19 cases in West Java.
Figure 5 compares model predictions and real data on vulnerable or susceptible (S) populations. Based on the graph, it is known that the parameters used in this study are suitable for use in numerical simulations, as evidenced by the identical shapes of the model prediction plots and real data. The graph indicates that the model’s predictions are accurate compared to the original data, and the parameters are fit for numerical simulations. The close alignment between the model predictions and actual data suggests that the model is effective in capturing the dynamics of COVID-19 cases in West Java. This validation of the parameters used enhances the reliability of the numerical simulations conducted in this study.
Figure 6 compares the predictions of the model with the real data on the infected (I) population.
To obtain the prediction graph of the model in I, Equation (34) is used. Based on the graph, it is known that the prediction results of the model are in accordance with the real data. This is evident from the simulation graph, which is identical to the original data. This alignment between the model predictions and actual data validates the accuracy of the parameters utilized in the study. The consistency between the simulation graph and real data further supports the reliability of the numerical simulations conducted. This means that the model’s predictions are accurate compared to the original data, and the parameters are fit for numerical simulations. Overall, the close match between the simulation results and real data indicates that the model is a reliable tool for predicting outcomes in similar scenarios. The successful validation of the parameters used in the study enhances the credibility of the numerical simulations performed.
4.4. Numerical Simulation Results
This numerical simulation’s objective is to depict the population dynamics in the COVID-19 pandemic. To obtain a simulation graph of each population compartment, apply Equations (33)–(37). The simulation graph will provide a visual representation of how each population compartment changes over time based on the equations provided. This will allow for a better understanding of the dynamics of the COVID-19 pandemic and help in making informed decisions regarding public health measures. The numerical simulation in this work makes use of the parameters presented in
Table 1.
Figure 8,
Figure 9 and
Figure 10 depict the COVID-19 population patterns in West Java with various scenarios.
Figure 8 shows the results of numerical simulations of the spread of the COVID-19-infected population using the model that has been formed. In
Figure 8, the scenario used is the scenario without intervention. The simulation illustrates a rapid increase in the number of infected individuals over time, highlighting the importance of implementing interventions to control the spread of the virus. These findings emphasize the potential impact of preventative measures on mitigating the effects of the pandemic.
Figure 8 shows that without intervention, the COVID-19 cases experienced are very high. In addition, in the scenario without intervention from the government, it was found that patient rejection occurred twice, namely in August 2021 and February 2022. This indicates that without intervention, the healthcare system in West Java may become overwhelmed, leading to patient rejection. Therefore, it is crucial for authorities to enforce strict measures such as lockdowns, mask mandates, and social distancing to prevent such a scenario. Implementing these interventions can help reduce the burden on healthcare facilities and ultimately save lives. The data from
Figure 8 highlights the importance of implementing effective measures to control the spread of COVID-19 in order to prevent such high numbers of cases and potential healthcare system strain.
Figure 9 shows the results of numerical simulations of the spread of the COVID-19-infected population using the model that has been formed. In
Figure 9, the scenario used is the scenario with social distancing intervention. The simulation results indicate a significant reduction in the number of infected individuals compared to scenarios without social distancing measures. This highlights the effectiveness of implementing social distancing interventions in controlling the spread of COVID-19.
Figure 9 shows that with social distancing intervention, the COVID-19 cases experienced have decreased when compared to without intervention. In addition, in the scenario with social distancing intervention, it was found that patient rejection occurred twice, namely in August 2021 and February 2022, with a smaller number of rejections compared to without intervention. These findings suggest that social distancing measures have played a crucial role in reducing the burden on healthcare systems by preventing a surge in cases. The data underscores the importance of continuing to adhere to these interventions to mitigate the impact of the pandemic. These findings suggest that implementing social distancing measures can effectively reduce the spread of COVID-19 and decrease the number of patient rejections. The results highlight the importance of proactive interventions in controlling the pandemic and minimizing healthcare system strain.
Figure 10 shows the results of numerical simulations of the spread of the COVID-19-infected population using the model that has been formed. In
Figure 10, the scenario used is the scenario with lockdown intervention.
Figure 10 shows that with lockdown intervention, the COVID-19 cases experienced have decreased when compared to no intervention and social distancing. In addition, in the scenario with lockdown intervention, it was found that patient rejection only occurred once, in February 2022, with a smaller number of rejections when compared to no intervention and social distancing. Overall, the results suggest that implementing a lockdown intervention can effectively reduce the spread of COVID-19 and minimize patient rejections. This highlights the importance of strict measures for controlling the pandemic and protecting public health.
Based on
Figure 8,
Figure 9 and
Figure 10, it is found that, in general, the number of patients who have severe symptoms and need treatment is 0, meaning that in most time intervals, all COVID-19 patients with severe symptoms will obtain treatment despite the increase in infected cases. This suggests that the healthcare system in West Java is able to effectively manage the influx of severe COVID-19 cases. The data from this simulation can be valuable for policymakers in determining the effectiveness of different public health measures. However, when the spike in infected cases is too high, for example, in June 2021 and January 2022, this will cause the hospital to be unable to handle the spike in cases and result in COVID-19 patients being rejected or not receiving treatment. When reviewed based on the scenario used, it was found that in the social distancing scenario, the number of patient rejections was less than without intervention, whereas in the lockdown scenario, there were only rejections in the January 2022 period. This highlights the importance of implementing timely and effective public health measures to prevent overwhelming healthcare systems during spikes in cases. It also underscores the need for continuous monitoring and adjustment of strategies based on simulation outcomes to ensure optimal outcomes. To determine how the impact on health costs needs to be prepared, Equations (40) and (41) are used. The graph of the costs that need to be prepared by the government is presented in
Figure 11,
Figure 12 and
Figure 13.
Figure 11 shows the estimated cost of handling the COVID-19 pandemic based on the modeling results. The cost projections take into account various factors such as healthcare expenses, economic impacts, and government response measures. It is important to note that these estimates are subject to change based on the evolving nature of the pandemic and the effectiveness of containment efforts.
Figure 11 shows that there is a spike in handling costs in the periods of August 2021 and February 2022.
Figure 11 shows that there was also a surge in COVID-19 cases and patient rejection in the same period. These spikes in handling costs coincide with peaks in COVID-19 cases and patient rejection rates, indicating a direct correlation between the two. This information can help policymakers and healthcare providers better anticipate and allocate resources during future surges in the pandemic. This shows that the rejection of COVID-19 patients can increase the costs that need to be incurred by the government. This is because the government must accommodate all COVID-19 patients, and when there are cases of rejection, the bed capacity needs to be increased, and this causes a surge in the cost of handling the COVID-19 pandemic.
Figure 12 shows the estimated cost of handling the COVID-19 pandemic based on the modeling results. Based on
Figure 12, the costs that need to be incurred for handling a pandemic with a social distancing scenario are less than without any intervention. This suggests that implementing social distancing measures can help reduce the financial burden associated with managing a pandemic. It is crucial for policymakers to consider these cost estimates when making decisions about public health interventions. In addition,
Figure 12 shows that there is a spike in handling costs in the periods of August 2021 and February 2022, with a smaller amount when compared to the scenario without any intervention.
Figure 9 shows that there was also a spike in COVID-19 cases and patient rejection during the same period. This shows that the rejection of COVID-19 patients can increase the costs that need to be incurred by the government. This is because the government must accommodate all COVID-19 patients, and when there are cases of rejection, the bed capacity needs to be increased, and this causes a surge in the cost of handling the COVID-19 pandemic. Therefore, reducing patient rejection can help mitigate the financial burden on the government and healthcare system. Implementing strategies to address patient rejection, such as improving communication and coordination between healthcare facilities, could lead to more efficient use of resources and ultimately lower costs in managing the pandemic.
Figure 13 shows the estimated cost of handling the COVID-19 pandemic based on the modeling results with the lockdown scenario. The estimated cost includes healthcare expenses, economic losses, and government stimulus packages. It is crucial for policymakers to consider these projections when making decisions regarding public health measures and economic recovery plans. Based on
Figure 13, the costs that need to be incurred for handling a pandemic with a lockdown scenario are less than without any intervention. In addition,
Figure 13 shows that there is a spike in handling costs in the periods of August 2021 and February 2022, with a smaller amount when compared to the scenario without intervention. This suggests that implementing a lockdown can help mitigate the overall costs associated with a pandemic. However, it is important to carefully weigh the economic impact of such measures against their potential benefits in terms of public health and long-term recovery. In
Figure 10, it is shown that there was also a spike in COVID-19 cases and patient rejection during the same period. This shows that the rejection of COVID-19 patients can increase the costs incurred by the government. This is because the government must accommodate all COVID-19 patients, and when there are cases of rejection, the bed capacity needs to be increased; this causes a surge in the cost of handling the COVID-19 pandemic. This leads to a strain on resources and funding for other important public health initiatives. It is crucial for governments to address patient rejection issues promptly to ensure efficient allocation of resources and prevent unnecessary strain on the healthcare system. By implementing strategies to reduce patient rejection rates, governments can better manage the financial burden of the COVID-19 pandemic and prioritize funding for various public health initiatives.
Based on
Figure 11,
Figure 12 and
Figure 13, it was found that the cost of handling COVID-19 increased when the number of existing COVID-19 patients also increased. In addition, it was also found that after the spike occurred, the cost of handling COVID-19 cases decreased and tended to remain low until the next spike occurred. Therefore, it is crucial for the government to closely monitor the number of existing COVID-19 patients in order to anticipate and prepare for potential spikes in health costs. By using Equations (40) and (41) and analyzing the graph in
Figure 8,
Figure 9 and
Figure 10, policymakers can make informed decisions to effectively manage and allocate resources for handling COVID-19 cases. This suggests that there is increased public awareness after a spike in cases, leading to a reduction in the number of COVID-19 cases so that people begin to feel safe again and relax health protocols, which causes the number of COVID-19 cases to increase again. It is crucial for policymakers to closely follow trends and patterns in COVID-19 cases to implement timely interventions and prevent overwhelming healthcare systems. By continuously monitoring and adjusting strategies based on data analysis, the impact of potential spikes in health costs can be minimized. Based on
Figure 11,
Figure 12 and
Figure 13, it is found that the highest total cost is experienced by scenario 3 with lockdown intervention, which is 73 billion IDR; the highest cost is followed by scenario 1 with no intervention scenario, which has a cost of 67.42 billion IDR; and the smallest cost is experienced by scenario 2, which costs 32.872 billion IDR. These findings suggest that implementing a lockdown intervention can lead to higher total costs compared to scenarios with no intervention. It is crucial for policymakers to carefully consider the economic implications of different strategies for managing COVID-19 outbreaks.