scholarly journals Stability and optimal control of a delayed HIV/AIDS-PrEP model

2021 ◽  
Vol 0 (0) ◽  
pp. 0
Author(s):  
Cristiana J. Silva
Keyword(s):  
Optimal Control ◽  
Hiv Infection ◽  
Equilibrium Points ◽  
Minimum Principle ◽  
Existence And Stability ◽  
Prep Implementation ◽  
Exposure Prophylaxis ◽  
The Impact ◽  
Number Of Individuals ◽  
Hiv Aids

<p style='text-indent:20px;'>In this paper, we propose a time-delayed HIV/AIDS-PrEP model which takes into account the delay on pre-exposure prophylaxis (PrEP) distribution and adherence by uninfected persons that are in high risk of HIV infection, and analyze the impact of this delay on the number of individuals with HIV infection. We prove the existence and stability of two equilibrium points, for any positive time delay. After, an optimal control problem with state and control delays is proposed and analyzed, where the aim is to find the optimal strategy for PrEP implementation that minimizes the number of individuals with HIV infection, with minimal costs. Different scenarios are studied, for which the solutions derived from the Minimum Principle for Multiple Delayed Optimal Control Problems change depending on the values of the time delays and the weights constants associated with the number of HIV infected individuals and PrEP. We observe that changes on the weights constants can lead to a passage from <i>bang-singular-bang</i> to <i>bang-bang</i> extremal controls.</p>

scholarly journals Modeling the Impact of Screening on the Transmission Dynamics of Human Papillomavirus with Optimal Control

2021 ◽  
Vol 16 ◽  
pp. 735-754
Author(s):  
Eshetu Dadi Gurmu ◽  
Boka Kumsa Bola ◽  
Purnachandra Rao Koya
Keyword(s):  
Optimal Control ◽  
Human Papillomavirus ◽  
Disease Transmission ◽  
Control Strategies ◽  
Equilibrium Points ◽  
Screening Strategy ◽  
Existence And Stability ◽  
The Stability ◽  
The Impact ◽  
Disease Free

In this study, a nonlinear deterministic mathematical model of Human Papillomavirus was formulated. The model is studied qualitatively using the stability theory of differential equations. The model is analyzed qualitatively for validating the existence and stability of disease ¬free and endemic equilibrium points using a basic reproduction number that governs the disease transmission. It's observed that the model exhibits a backward bifurcation and the sensitivity analysis is performed. The optimal control problem is designed by applying Pontryagin maximum principle with three control strategies viz. prevention strategy, treatment strategy, and screening strategy. Numerical results of the optimal control model reveal that a combination of prevention, screening, and treatment is the most effective strategy to wipe out the disease in the community.

scholarly journals Bifurcation analysis and optimal control of SEIR epidemic model with saturated treatment function on the network

2021 ◽  
Vol 19 (2) ◽  
pp. 1677-1695
Author(s):  
Boli Xie ◽  
◽  
Maoxing Liu ◽  
Lei Zhang
Keyword(s):  
Optimal Control ◽  
Disease Transmission ◽  
Equilibrium Points ◽  
Virus Transmission ◽  
Population Heterogeneity ◽  
Multiple Equilibrium ◽  
Optimal Control Strategy ◽  
Treatment Function ◽  
The Stability ◽  
The Impact

<abstract><p>In order to study the impact of limited medical resources and population heterogeneity on disease transmission, a SEIR model based on a complex network with saturation processing function is proposed. This paper first proved that a backward bifurcation occurs under certain conditions, which means that $ R_{0} &lt; 1 $ is not enough to eradicate this disease from the population. However, if the direction is positive, we find that within a certain parameter range, there may be multiple equilibrium points near $ R_{0} = 1 $. Secondly, the influence of population heterogeneity on virus transmission is analyzed, and the optimal control theory is used to further study the time-varying control of the disease. Finally, numerical simulations verify the stability of the system and the effectiveness of the optimal control strategy.</p></abstract>

Dynamical analysis of a class of hepatitis C virus infection models with application of optimal control

2016 ◽  
Vol 09 (03) ◽  
pp. 1650038 ◽  
Author(s):  
Aida Mojaver ◽  
Hossein Kheiri
Keyword(s):  
Optimal Control ◽  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Deterministic Model ◽  
Treatment Strategies ◽  
Dynamical Analysis ◽  
Existence And Stability ◽  
Direct Cell ◽  
Infected Cells ◽  
The Impact

In this paper, we deal with the problem of optimal control of a deterministic model of hepatitis C virus (HCV). In the first part of our analysis, a mathematical modeling of HCV dynamics which can be controlled by antiretroviral therapy as fixed controls has been presented and analyzed which incorporates two mechanisms: infection by free virions and the direct cell-to-cell transmission. Basic reproduction number is calculated and the existence and stability of equilibria are investigated. In the second part, the optimal control problem representing drug treatment strategies of the model is explored considering control parameters as time-dependent in order to minimize not only the population of infected cells but also the associated costs. At the end of the paper, the impact of combination of the strategies in the control of HCV and their effectiveness are compared by numerical simulation.

THE EFFECTS OF VACCINATION AND TREATMENT ON THE SPREAD OF HIV/AIDS

2004 ◽  
Vol 12 (04) ◽  
pp. 399-417 ◽  
Author(s):  
M. KGOSIMORE ◽  
E. M. LUNGU
Keyword(s):  
Equilibrium Point ◽  
Reproduction Number ◽  
Equilibrium Points ◽  
Treatment Programs ◽  
Asymptotically Stable ◽  
Reproduction Numbers ◽  
Threshold Conditions ◽  
Existence And Stability ◽  
Disease Free ◽  
Hiv Aids

This study investigates the effects of vaccination and treatment on the spread of HIV/AIDS. The objectives are (i) to derive conditions for the success of vaccination and treatment programs and (ii) to derive threshold conditions for the existence and stability of equilibria in terms of the effective reproduction number R. It is found, firstly, that the success of a vaccination and treatment program is achieved when R0t<R0, R0t<R0v and γeRVT(σ)<RUT(α), where R0t and R0v are respectively the reproduction numbers for populations consisting entirely of treated and vaccinated individuals, R0 is the basic reproduction number in the absence of any intervention, RUT(α) and RVT(σ) are respectively the reproduction numbers in the presence of a treatment (α) and a combination of vaccination and treatment (σ) strategies. Secondly, that if R<1, there exists a unique disease free equilibrium point which is locally asymptotically stable, while if R>1 there exists a unique locally asymptotically stable endemic equilibrium point, and that the two equilibrium points coalesce at R=1. Lastly, it is concluded heuristically that the stable disease free equilibrium point exists when the conditions R0t<R0, R0t<R0v and γeRVT(σ)<RUT(α) are satisfied.

scholarly journals State-Based Switching for Optimal Control of Computer Virus Propagation with External Device Blocking

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Qingyi Zhu ◽  
Seng W. Loke ◽  
Ye Zhang
Keyword(s):  
Optimal Control ◽  
Control Strategies ◽  
Minimum Principle ◽  
Optimal Solution ◽  
Computer Virus ◽  
Numerical Results ◽  
Difference Approximation ◽  
External Device ◽  
Virus Propagation ◽  
The Impact

The rapid propagation of computer virus is one of the greatest threats to current cybersecurity. This work deals with the optimal control problem of virus propagation among computers and external devices. To formulate this problem, two control strategies are introduced: (a) external device blocking, which means prohibiting a fraction of connections between external devices and computers, and (b) computer reconstruction, which includes updating or reinstalling of some infected computers. Then the combination of both the impact of infection and the cost of controls is minimized. In contrast with previous works, this paper takes into account a state-based cost weight index in the objection function instead of a fixed one. By using Pontryagin’s minimum principle and a modified forward-backward difference approximation algorithm, the optimal solution of the system is investigated and numerically solved. Then numerical results show the flexibility of proposed approach compared to the regular optimal control. More numerical results are also given to evaluate the performance of our approach with respect to various weight indexes.

Controlling Asthma Due to Air Pollution

2020 ◽  
pp. 1-22
Author(s):  
Ankush H. Suthar ◽  
Purvi M. Pandya
Keyword(s):  
Mathematical Model ◽  
Optimal Control ◽  
Air Pollution ◽  
Control Theory ◽  
Global Stability ◽  
Optimal Control Theory ◽  
Positive Impact ◽  
Equilibrium Points ◽  
Local And Global Stability ◽  
Number Of Individuals

The health of our respiratory systems is directly affected by the atmosphere. Nowadays, eruption of respiratory disease and malfunctioning of lung due to the presence of harmful particles in the air is one of the most sever challenge. In this chapter, association between air pollution-related respiratory diseases, namely dyspnea, cough, and asthma, is analysed by constructing a mathematical model. Local and global stability of the equilibrium points is proved. Optimal control theory is applied in the model to optimize stability of the model. Applied optimal control theory contains four control variables, among which first control helps to reduce number of individuals who are exposed to air pollutants and the remaining three controls help to reduce the spread and exacerbation of asthma. The positive impact of controls on the model and intensity of asthma under the influence of dyspnea and cough is observed graphically by simulating the model.

scholarly journals Dynamical Behaviour of a Tumor-Immune System with Chemotherapy and Optimal Control

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Swarnali Sharma ◽  
G. P. Samanta
Keyword(s):  
Optimal Control ◽  
T Cells ◽  
Tumor Cells ◽  
Equilibrium Points ◽  
Dynamical Behaviour ◽  
Helper T Cells ◽  
Chemotherapeutic Drug ◽  
Tumor Growth Model ◽  
Existence And Stability ◽  
Set Up

We have considered a tumor growth model with the effect of tumor-immune interaction and chemotherapeutic drug. We have considered two immune components—helper (resting) T-cells which stimulate CTLs and convert them into active (hunting) CTL cells and active (hunting) CTL cells which attack, destroy, or ingest the tumor cells. In our model there are four compartments, namely, tumor cells, active CTL cells, helper T-cells, and chemotherapeutic drug. We have discussed the behaviour of the solutions of our system. The dynamical behaviour of our system by analyzing the existence and stability of the system at various equilibrium points is discussed elaborately. We have set up an optimal control problem relative to the model so as to minimize the number of tumor cells and the chemotherapeutic drug administration. Here we used a quadratic control to quantify this goal and have considered the administration of chemotherapy drug as control to reduce the spread of the disease. The important mathematical findings for the dynamical behaviour of the tumor-immune model with control are also numerically verified using MATLAB. Finally, epidemiological implications of our analytical findings are addressed critically.

scholarly journals Optimal control problem arises from illegal poaching of southern white rhino mathematical model

2020 ◽  
Vol 2020 (1) ◽  
Author(s):  
Dipo Aldila ◽  
Nadhira Azizah ◽  
Bevina D. Handari
Keyword(s):  
Optimal Control ◽  
Cost Effectiveness ◽  
Equilibrium Points ◽  
Minimum Principle ◽  
Cost Effectiveness Ratio ◽  
Indicator Method ◽  
Threshold Functions ◽  
Predator Prey Model ◽  
White Rhino ◽  
Analytical Result

Abstract In this paper, a novel dynamical population model of a southern white rhino with legal and illegal poaching activity is introduced. The model constructed is based on a predator–prey model with southern white rhinos as prey and humans (hunters) as predators. We divide the southern white rhino population into three classes based on their horn condition. We investigate the existence and the stability of the equilibrium points, which depend on some threshold functions. From an analytical result, it is trivial that arresting as many hunters as possible helps conserve white rhinos, but it comes at a high cost. Therefore, an optimal strategy is needed. The optimal control is then constructed using Pontryagin’s minimum principle and solved numerically with an iterative forward–backward method. Optimal control simulations are given to provide additional insight into the dynamics of the model. Analysis of the cost function effectiveness is conducted using the ACER (Average Cost–Effectiveness Ratio) and ICER (Incremental Cost–Effectiveness Ratio) indicator method. The results show that the hunter population can be more easily controlled with a time-dependent hunter arrest rate rather than by treating it as a constant.

MODELING VACCINE PREVENTABLE VECTOR-BORNE INFECTIONS: YELLOW FEVER AS A CASE STUDY

2016 ◽  
Vol 24 (02n03) ◽  
pp. 193-216 ◽  
Author(s):  
SILVIA MARTORANO RAIMUNDO ◽  
HYUN MO YANG ◽  
EDUARDO MASSAD
Keyword(s):  
Mortality Rate ◽  
Yellow Fever ◽  
Deterministic Model ◽  
Equilibrium Points ◽  
Vaccination Rate ◽  
Sensitivity Analyses ◽  
Existence And Stability ◽  
Vector Borne ◽  
The Impact

In this paper, we propose and simulate a deterministic model for a vector-borne disease in the presence of a vaccine. The model allows the assessment of the impact of an imperfect vaccine with various characteristics, which include waning protective immunity, incomplete vaccine-induced protection and adverse events. We find three threshold parameters which govern the existence and stability of the equilibrium points. Our stability analysis suggests that the reduction in the mosquito fertility theoretically is the most effective factor of reducing disease prevalence in both low and high transmission areas. To illustrate the theoretical results, the model is simulated by the example of yellow fever. We also perform sensitivity analyses to determine the importance of both vaccine-induced mortality rate and disease-induced mortality rate for determining a control strategy. We found that there is an optimum vaccination rate, above which people die by the vaccination and below which people die by the disease.

scholarly journals The impact of armed conflict on the prevalence and transmission dynamics of HIV Infection in Libya.

2021 ◽  
Author(s):  
Mohamed A Daw ◽  
Abdallah HU El-Bouzedi ◽  
Mohamed O Ahmed
Keyword(s):  
Hiv Infection ◽  
Armed Conflict ◽  
Transmission Dynamics ◽  
Eastern Region ◽  
Internally Displaced ◽  
Infected People ◽  
Post Conflict ◽  
Displaced People ◽  
The Impact ◽  
Hiv Aids

ABSTRACT The interrelationships between HIV/AIDS and armed conflict are a complex phenomenon and studies are rarely devoted to this area of research. Libya is the second-largest country in Africa that has been evoked with war since NATO intervention in 2011. The country has also experienced one of the largest HIV outbreaks associated with the Bulgarian Nurses saga. The effect of the armed conflict on the dynamic spread of HIV is not well known. The objectives of this study were to determine the impact of armed conflict on the epidemiological situation of HIV infection in Libya and analyze the transmission dynamics of HIV strains during the conflict. We investigated the movement of HIV-infected people during the Libyan armed conflict and analyzed the HIV subtypes reported from 2011 to 2020 and followed up the infected cases all over the country. The patterns of HIV spread within the Libyan regions were traced and risk factors were determined during the conflict period. A total of 4539 HIV/AIDS patients were studied from the four regions during the Libyan conflict. Our data analysis indicated that Benghazi the biggest city in the Eastern region was the significant exporter of the virus to the rest of the country. Viral dissemination changes were observed within the country particularly after 2015. A major virus- flow from the Eastern region during the armed conflict associated with internally displaced people. This resulted in a dissemination of new HIV strains and accumulations of HIV cases in Western and Meddle regions. Although, there were no significant changes in the national prevalence of HIV/AIDS. Our data highlights the factors that complicated the spread and dissemination of HIV during the armed conflict which provides a better understanding of the interaction between them. This could be used to plan for effective preventive measures in tackling the spread of HIV in conflict and post-conflict settings.

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