Search

This paper deals with the non-linear Susceptible–Infected–Hospitalized–Recovered model with Holling type II incidence rate, treatment with saturated type functional response for the prevention and control of disease with limited healthcare facilities. The well-posedness of the model is ensured with the help of the non-negativity and boundedness of the solution of the system. The feasibility of the model with DFE (Disease-free equilibrium) and EE (endemic equilibrium) is analysed. The local and global stability are discussed with the help of the computed basic reproduction number R 0. At R 0 = 1 , we use the Centre manifold theory to analyse the transcritical bifurcation exhibited by the system. It is found that the disease is not eradicated even if R 0 < 1 due to the occurrence of backward bifurcation. The occurrence condition of Hopf bifurcation is obtained. The optimal control theory is used to analyse the effects of the minimum possible medical facilities, hospital beds, and awareness creation on the population dynamics. The Hamiltonian function is constructed with the extended optimal control model and solved by Pontryagin's maximum principle to get the minimum possible expenditure. Different types of control strategies are shown by numerical simulation. The sensitivity analysis is discussed with the help of a crucial parameter that depends on the reproduction number. Further, the model is simulated numerically to support the theoretical studies. This paper emphasizes the significance of treatment intensity, the total number of hospital bed available and their occupancy rate as vital parameters for prevention of disease prevalence. • A nonlinear model is proposed to study the spread and control of infectious diseases with limited healthcare facilities. • Due to backward bifurcation, R 0 < 1 is insufficient to eliminate the disease, and the system exhibits periodic oscillation due to the emergence of Hopf bifurcation. • Using Pontryagin's maximum principle, effects of the limited medical facilities, hospital beds, and awareness-building initiatives are examined to determine the minimum possible expenses. • Sensitivity analysis is used to determine the appropriate control parameter and cost-effectiveness analysis is used for finding most optimal strategy. [ABSTRACT FROM AUTHOR]

In this paper, a class of virus-to-cell HIV model with intracellular delays, saturated incidence and Logistic growth is proposed to characterize the interaction between two types HIV strains, i.e., wild-type and drug-resistant strains. First, a series of threshold criteria on the locally and globally asymptotic stability of (infection-free, dominant, coexistence) equilibria are discussed based on the basic reproduction number R 0. Furthermore, a detailed Hopf bifurcation analysis is performed on the coexistence equilibrium using two delays as bifurcation parameters. We find that the Hopf bifurcations induced by double-strains are evidently different and more complicated than that of single strain, the former switches from stability (periodic branches) to un-stability (chaos) more frequently and earlier than the latter since double-strains would yield more pairs of imaginary roots in the characteristic equations. Meanwhile, the total viral load of double-strains would be higher than that of single-strain as well. The emergence of drug resistance imposes either negative or positive influences on the survival of wild-type strain, which would further facilitate the transmission of HIV. [ABSTRACT FROM AUTHOR]

The spreading of HIV or HTLV-I among the cells has received the great attention in recent modelling study to explore the virus infection dynamics. The co-infection of HIV and HTLV-I with the effect of Cytotoxic T-lymphocytes (CTLs) immune response is also important from epidemiological point of view. To identify the co-infection scenario of HIV and HTLV-I with the CTLs effect we proposed in this paper a six compartmental ODE-model with uninfected, HIV-infected, HTLV-I infected CD4+T cells and free HIV virus particles with HIV specific CTLs and HTLV-I specific CTLs. The rates of infection of the cases are considered here saturated type and proliferation rate of uninfected and HIV infected CD4+ T-cells are of logistic terms. To establish the well-posedness of the model we have shown that the solution of the proposed model is non-negative and bounded. We obtain the basic reproduction number which is the maximum of the HIV-related reproduction and the HTLV-I related reproduction number. Along with the disease free equilibrium point the system contains other seven endemic equilibrium points containing infection by single disease or both. Analytically, we establish the local and global stability conditions of the equilibrium points and also we establish that the system experiences transcritical bifurcation by the generation of only HIV or HTLV-I infected endemic equilibrium point. Using numerical simulations, we validate the theoretical results and found two infection paths, one initiating with HIV and other with HTLV-I, both cases ultimately become co-infected. Finally, using the optimal control analysis we found the optimal policy for treatment using AVR, RTI & PI for HIV or AZT for HTLV-I control and lastly concluded by some recommendations. • A co-infected HIV & HTLV-I infection model in vivo. • Proliferation of CD4+ T-cells are taken in logistic form. • Incidence rate is taken as saturated type. • Verified competitive exclusive principle. • Spreading path has been studied using Flow-diagram. • Three types of control strategies are investigated. [ABSTRACT FROM AUTHOR]

In this paper, a stochastic HIV/AIDS epidemic model is presented to study the synthetic effect of ART (antiretroviral therapy) and PrEP (pre-exposure prophylaxis) treatments among MSM (men who have sex with men). Firstly, we give the global stability of disease-free equilibrium and the endemic equilibrium in terms of basic reproduction number R 0 for deterministic model. And then the existence of global positive solutions and the existence of unique ergodic stationary distribution under R 0 S > 1 for stochastic model are given. Further, the long-time stochastic dynamic of the model is investigated, including the criteria on the extinction and persistence in mean for the stochastic model. Finally, we give some numerical simulations to illustrate our theoretical results, and the sensitive analysis shows that ART (antiretroviral therapy) and PrEP (pre-exposure prophylaxis) treatments can effectively control the spread of AIDS among MSM population. [ABSTRACT FROM AUTHOR]

This paper aims to study an HIV model with age structure and latently in a spatially homogeneous environment. By applying the fixed point theorem, we obtain the existence of the global solution and the global attractor for the model. We also identify the explicit formula of the basic reproduction number by the mean of the Laplace transformation, and confirm that this number predicts whether the infection occurs or not. Through analyzing the root distribution of the characteristic equation, the local stability of the equilibrium is obtained. By appealing to the appropriate Lyapunov functionals, we further study the global stability of the equilibrium. Numerical simulations also validate our theoretical results. [ABSTRACT FROM AUTHOR]

Air pollution has a serious impact on the spread of respiratory infectious diseases. However, the concentration of air pollution is not the same in different places. In order to characterize the spatial heterogeneity and the diffusion of pollutants, this paper proposes a spatial heterogeneity model, where the transmission rate is closely related to air pollution. The dynamics are established in terms of the basic reproduction number R 0 : if R 0 ≤ 1 , the disease-free equilibrium is globally asymptotically stable; if R 0 > 1 , there exists at least one endemic equilibrium and the disease is uniformly persistent. Our findings suggest that spatial heterogeneity, increased pollutants emission, and limited movement of infected individuals will all contribute to the spread of the respiratory infectious diseases. Subsequently, the corresponding strategies are introduced into the model to control the prevalence of the diseases. Under the minimization of the objective function, the necessary condition for the optimal control is acquired with the help of Pontryagin's maximum principle. Numerical simulations are applied to validate the theoretical results of threshold dynamics and to demonstrate the influences of inflow and clearance rates of pollutants on threshold dynamics and optimal control. [ABSTRACT FROM AUTHOR]

Antiretroviral (ART) drugs have been used to treat HIV patients over last two decades. But, the daily use of these drugs in order to control HIV load in patients' body results different side effects and high cost over long period of time. Motivated by these, researchers have been trying to find other treatment strategy whose combination with antiretroviral treatments can control HIV without use of large quantities of drugs. Immunotherapy is one of such treatment which assist natural immune system of patients in order to get control over viral infection. Administration of immunotherapy in combination with antiretroviral drugs has been found safe and effective after different clinical trials on humans and other animals. In this paper, we propose a mathematical model to describe HIV dynamics under antiretroviral treatment and immunotherapy combination. We find that our model is biologically feasible and the findings of the clinical trials support the dynamics of our model. The stability analyses of HIV-free equilibrium point are performed and found the basic reproduction number as a threshold parameter. Also, we calculate a critical efficacy for overall antiretroviral treatment such that when the efficacy of overall treatment exceeds this value HIV will be completely removed. Also, we have found that critical drug efficacy for antiretroviral drugs decreases with increasing immunotherapy, which indicates combination of immunotherapy with antiretroviral treatments minimize the quantity of antiretroviral drugs for HIV eradication, hence minimize the side effects and cost of antiretroviral drugs. Numerical simulations are carried out to substantiate the analytical results and to illustrate different drug administration scenarios. Moreover, an optimal combination of drugs which can control HIV with lower costs and side effects, is obtained by solving an optimal control problem numerically. [ABSTRACT FROM AUTHOR]

In this paper, we present a delayed deterministic and stochastic S I R I C V models to investigate the effects of the white noise intensities and the waning immunity of vaccinated individuals in the evolution of the disease. For the deterministic S I R I C V model, the basic reproduction number R 0 and the equilibrium points are calculated. The local stability of equilibrium points is analyzed. Particularly, when R 0 < 1 the disease-free equilibrium is locally stable for any positive value of τ. Furthermore, when R 0 > 1 , the local stability and sufficient conditions to ensure the occurrence of Hopf bifurcation for the endemic equilibrium point are established by considering the time delay τ as a bifurcation parameter. For the stochastic S I R I C V model, the conditions of the extinction and persistence of the disease are given by using the stochastic basic reproduction numbers R 0 s and R 0 s ∗. Numerical simulations are presented to enhance our analytical results and contrast the deterministic and stochastic models. [ABSTRACT FROM AUTHOR]

In this paper, a novel COVID-19 reaction–diffusion model with virus mutation and media coverage is investigated. First, the solution's uniform boundedness for the system is established. Then, the basic reproduction numbers for ordinary and mutant viruses spread in heterogeneous environments are defined. Furthermore, the endemic equilibrium's asymptotic distribution for the system is explored. In addition, when one diffusion coefficient tends to zero and the other diffusion coefficients are greater than zero and fixed, the solution of the system will asymptotically approach endemic equilibrium. Next, a theoretical analysis of how high-frequency media coverage affects the development of the COVID-19 epidemic is conducted. Theoretical research shows that high-frequency media coverage will lead to the disappearance of the disease. Meantime, global sensitivity analysis on the basic reproduction numbers R 01 and R 02 are performed. Finally, theoretical simulations and instance predictions are carried out. Because of the complexity of the Shanghai epidemic and changes in management and control, the infection rates β 1 (t) , β 2 (t) are given in the form of a piecewise function with more practical significance, and they are used to predict the epidemic trend of COVID-19 in Shanghai. Through a series of numerical simulations and analysis, the key indicators of the Shanghai COVID-19 epidemic are as follows : (1) The basic reproduction numbers in the early, middle, and late stages of COVID-19 are R ¯ 0 (1 : 34) = 0. 9152 , R ¯ 0 (35 : 49) = 3. 1476 , and R ¯ 0 (50 : 140) = 0. 6547 , respectively; (2) This epidemic round in Shanghai will peak at 3,270 new daily confirmed cases on the 49th day (April 15); (3) The final size of the epidemic will reach 63,470 confirmed cases; (4) This round of COVID-19 epidemic in Shanghai, China, is expected to be fully cleared in late June to early July. The above conclusions are basically consistent with the facts. Of course, with the rise in temperature and strict control, the epidemic situation in Shanghai, China, is expected to be cleared earlier. Our results provide new ideas for preventing and controlling the COVID-19 epidemic. • A reaction–diffusion model with virus mutation and media coverage is proposed. • The asymptotic properties of endemic equilibrium with small diffusion are explored. • Global sensitivity analysis for R 01 and R 02 and are performed. • Applying piecewise functions β 1 (t) , β 2 (t) , to predict the Shanghai COVID-19 epidemic. • Key indicators of COVID-19, such as R 0 , peak, final scale, clear time are obtained. [ABSTRACT FROM AUTHOR]

In this paper, an age-structured infectious disease dynamical model that considers two diseases simultaneously but with limited medical resources is proposed and analyzed. The asymptotic smoothness and persistence of the solution semi-flow are investigated. Then conditions for the existence of a global attractor are derived, which means that disease persists when ℜ 0 > 1. By using a Lyapunov function, it is shown that the infection-free equilibrium is globally asymptotically stable if ℜ 0 < 1 and the infection equilibrium is globally asymptotically stable if ℜ 0 > 1. In the presence of limited medical resources, the results suggest that equitable distribution for the limited medical resources is significant when treating low-risk and high-risk diseases and that keeping a resource sharing coefficient at a moderate level helps to eliminate the disease. • We proposed an age-structured infectious disease model with limited medical resources. • some important parameters were included in ℜ 0. • ℜ 0 determines the global stability of the equilibria. • Discussions of the effects of the parameters and biological significance were provided. [ABSTRACT FROM AUTHOR]

In this paper, an epidemic model with homogeneous Dirichlet boundary condition is formulated to study the joint impact of spatial diffusion, infection age and treatment adherence on the HIV/AIDS transmission among humans. It is an interesting problem to understand the threshold dynamics of HIV/AIDS model with the above three factors. Since the complexity of the model and specificity of the boundary condition, there are two main mathematical challenges: i). the compactness of the solution map is not guaranteed; ii). the explicit expression of the basic reproduction cannot be given even if the parameters are spatially independent. We first discuss the well-posedness of the system, then we identify the basic reproduction number R 0 as the spectral radius of the next generation operator, followed by the global attractivity of disease-free steady state when R 0 < 1 , the uniform persistence of the disease and the existence of the endemic steady state when R 0 > 1. Numerical simulations are carried out to illustrate our theoretical results, which suggest that the diffusion of individuals has an opposite effect on the disease outbreaks, and improving the treatment compliance of HIV infected individuals can control HIV transmission among the population effectively. [ABSTRACT FROM AUTHOR]

In this paper, a three tier mathematical model describing the interactions between susceptible population, Covid-19 infected, diabetic population and Covid-19 infected, non diabetic population is proposed. Basic properties of such a dynamic model, namely, non negativity, boundedness of solutions, existence of disease-free and disease equilibria are studied and sufficient conditions are obtained. Basic reproduction number for the system is derived. Sufficient conditions on functionals and parameters of the system are obtained for the local as well as global stability of equilibria, thus, establishing the conditions for eventual prevalence of disease free or disease environment, as the case may be. The stability aspects are discussed in the context of basic reproduction number and vice versa. An important contribution of this article is that a novel technique is presented to estimate some key, influencing parameters of the system so that a pre-specified, assumed equilibrium state is approached eventually. This enables the society to prepare itself with the help of these key, influencing parameters so estimated. Several examples are provided to illustrate the results established and simulations are provided to visualize the examples. [ABSTRACT FROM AUTHOR]

This paper introduces a deterministic fractional-order epidemic model (FOEM) for studying the transmission dynamics of the human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS). The model highlights the substantial role of unaware and undetected HIV-infected individuals in spreading the disease. Control strategies, such as wielding condoms, level of preventive measures to avoid infection, and self-strictness of susceptibles in sexual contact, have been incorporated into the study. The basic reproduction number ℛ 0 α has been derived, which suggests the conditions for ensuring the persistence and elimination of the disease. Further, to validate the model, actual HIV data taken from Mexico and India separately have been used. The disease dynamics and its control in both countries are analyzed broadly. The values of biological parameters are estimated at which numerical solutions better match the actual data of HIV patients in the case of fractional-order (FO) instead of integer-order (IO). Moreover, in the light of ℛ 0 α , our findings forecast that the disease will abide in the population in Mexico, and at the same time, it will die out from India after a long time. [ABSTRACT FROM AUTHOR]

This paper aims to explore stability and bifurcations with control analysis of a co-infected two serotypes dengue model in presence of three controls, namely protection control, treatment control and mosquito killing efforts. First we analyze the model incorporating with constant controls then find the control path considering variable control. We examine biological feasibility of the considered model along with existence and stability criteria of different equilibrium with respect to basic reproduction number. Stability of serotype-I, serotype-II free equilibrium and positive co-existence equilibrium are investigated. Center manifold theorem is used to prove the stability of the co-infected endemic equilibrium. The model experiences Transcritical bifurcation with respect to basic reproduction number. Sensitivity analysis has been employed to identify most influential model parameters to control the infection. The time dependent optimal control problem is solved analytically and numerically using Pontryagin's maximum principle. At last efficiency analysis has been carried out to find out more suitable control to combat the dengue disease. It is established from the analysis, protection control with treatment is more powerful than mosquito killing efforts by humans with treatment for controlling dengue. [ABSTRACT FROM AUTHOR]

Adaptive behavior on networks leads to bifurcation and other special phenomenon, which has been proved for differential systems. In this paper, one will discuss the stability, bifurcation and chaos of the discrete pair epidemic model on adaptive networks, which will bring some new challenges. The stability of the disease free equilibrium and endemic equilibrium with respect to basic reproduction number R 0 is studied. Under certain conditions, as the time step-size increases, flip bifurcation that occurs at the endemic equilibrium is discussed, the period-doubling bifurcation and the chaos phenomenon of the system are exhibited, some figures are provided for illustration. According to the results in this paper, the dynamical behaviors of the discrete model are multitudinous and quite different from the continuous model. [ABSTRACT FROM AUTHOR]

In this paper, a mathematical model with a standard incidence rate is proposed to assess the role of media such as facebook, television, radio and tweeter in the mitigation of the outbreak of COVID-19. The basic reproduction number R 0 which is the threshold dynamics parameter between the disappearance and the persistence of the disease has been calculated. And, it is obvious to see that it varies directly to the number of hospitalized people, asymptomatic, symptomatic carriers and the impact of media coverage. The local and the global stabilities of the model have also been investigated by using the Routh–Hurwitz criterion and the Lyapunov's functional technique, respectively. Furthermore, we have performed a local sensitivity analysis to assess the impact of any variation in each one of the model parameter on the threshold R 0 and the course of the disease accordingly. We have also computed the approximative rate at which herd immunity will occur when any control measure is implemented. To finish, we have presented some numerical simulation results by using some available data from the literature to corroborate our theoretical findings. [ABSTRACT FROM AUTHOR]

In this paper, we proposed the stochastic perturbation to study the HIV viral dynamical model. The stochastic epidemic model of 2-LTR HIV infected patients is considered and we prove that the stochastic model admits a unique globally positive solution7 which is bounded and permanent. Then we analyze the necessary conditions for extinction and persistence of the disease by selecting the appropriate Lyapunov functions. The theoretical findings are confirmed by using suitable numerical experiments. [ABSTRACT FROM AUTHOR]

In this paper, the global dynamical behavior of non-linear infection-age SIR models is investigated visually by numerical processes. Firstly, for an age-independent SIR model with diseased mortality and isolation rates, it has been shown that the linearly implicit Euler method reproduces the local dynamical behavior. For the study of the numerical global stability, numerical removed individuals are introduced and then the global behavior is represented by numerical processes for any stepsize. Generally, the numerical global behavior of the linearly implicit Euler method applied to non-linear infection-age SIR model is investigated. Using an infinite-dimensional Leslie operator, the disease-free equilibrium point is globally asymptotically stable for numerical processes when the numerical basic reproduction number of R h < 1. The numerical endemic disease equilibriums are globally asymptotically stable when the numerical threshold R h > 1. It is much more important that the global behavior of the analytical solutions is visually displayed by the numerical processes for the sufficiently small stepsize h. Finally, numerical applications to some the influenza models including HIV models and SIR models with protections are shown to illustrate our analysis. [ABSTRACT FROM AUTHOR]

In this paper, we are concerned with the mathematical analysis of a host–pathogen model with diffusion, hyperinfectivity and nonlinear incidence. We define the basic reproduction number ℜ 0 by the spectral radius of the next generation operator, and study the relation between ℜ 0 and the principal eigenvalue of the problem linearized at the disease-free steady state (DFSS). Under some assumptions, we show the threshold property of ℜ 0 : if ℜ 0 < 1 , then the DFSS is globally asymptotically stable (GAS), whereas if ℜ 0 > 1 , then the system is uniformly persistent and a positive steady state (PSS) exists. Moreover, for the special case where all parameters are constants, we show that the PSS is GAS for ℜ 0 > 1. Numerical simulation suggests that the spatial heterogeneity could enhance the intensity of epidemic, whereas the diffusion effect could reduce it. [ABSTRACT FROM AUTHOR]

In this paper, a susceptible–exposed–infectious–recovered (SEIR) epidemic patch model with nonlinear incidence rate, vaccination and quarantine strategies is presented. According to the properties of nonnegative matrices, the range of basic reproduction number is obtained. Moreover, the stability of disease-free equilibrium is studied. Some numerical simulations are given to validate the theoretical results. The effects of vaccination, quarantine strategies and population migration on disease transmission are also investigated by numerical simulations. [ABSTRACT FROM AUTHOR]

In this paper, we perform a complete analysis on a degenerated reaction–diffusion cholera model with stabilizing total humans and non-mobility of cholera bacteria in a spatially heterogeneous bounded domain. The existence of a global attractor is established through introducing the Kuratowski measure of non-compactness. The basic reproduction number and its equivalent characterizations have been used to analyze the threshold-type results, where the persistence and extinction of cholera can also be characterized by the dispersal rate of infected humans. In the homogeneous case, the global attractivity of the unique positive equilibrium is achieved by the Lyapunov function. Moreover, we compare the basic reproduction numbers for the models without and with considering the mobility of cholera bacteria. Our results suggest that: the basic reproduction numbers attain different values as the dispersal rates of infected humans and cholera approach to infinity, while they attain the same value as the dispersal rates of infected humans and cholera approach to zero. Numerical simulations support our analytical results and discuss the impact of the dispersal rate of infected humans on the transmission of cholera. [ABSTRACT FROM AUTHOR]

The dynamics of COVID-19 pandemic varies across countries and it is important for​ researchers to study different kind of phenomena observed at different stages of the waves during the epidemic period. Our interest in this paper is not to model what happened during the endemic state but during the epidemic state. We proposed a continuous formulation of a unique maximum reproduction number estimate with an assumption that the epidemic curve is in form of the Gaussian curve and then compare the model with the discrete form and the observed basic reproduction number during the contagiousness period considered. Furthermore, we estimated the transmission rate from identification of the first inflection point of a wave of the curve of daily new infectious cases using the Bernoulli S–I (Susceptible–Infected) equation. We applied this new method to the real data from Cameroon COVID-19 outbreak both at national and regional levels. High correlation was observed between the socio-economic parameters and epidemiology parameters at regional level in Cameroon. Also, the method was applied to the second wave COVID-19 outbreak for the world data which is a period the phenomena we are considering were observed. Lastly, it was observed that the models presented results correspond with the epidemic dynamics in Cameroon and World data. We recommend that it is important to study what happened during the growth inflection point as some countries data did not climax. [ABSTRACT FROM AUTHOR]

Infectious disease transmission, mainly affected by media coverage and stochastic perturbations, has imposed great social financial burden on the community in the past few decades and even threatened public health. However, there are few studies devoted to the theoretical dynamics of epidemic models with media coverage and biologically reasonable stochastic effect yet. In this sense, this paper mainly formulates and studies a stochastic epidemic model with media coverage and two mean-reverting Ornstein–Uhlenbeck processes. We first illustrate the biological implication and mathematically reasonable assumption of introducing the Ornstein–Uhlenbeck process as stochastic effect. It is theoretically proved that the solution to the stochastic model is unique and global, as well as the existence of an ergodic stationary distribution. After that, by solving the corresponding Fokker–Planck equation and using our developed algebraic equation theory, it is derived that the above global solution around the endemic equilibrium follows a unique probability density function. For completeness, the sufficient criteria for extinction exponentially of the model are established. Finally, several numerical simulations are provided to verify our theoretical results. Besides, the impact of stochastic noises and media coverage on epidemic transmission is studied by comparison with the previous results of a deterministic model. [ABSTRACT FROM AUTHOR]

It is well known that the mathematical biology and dynamical systems give very important information for the study and research of viral infection models such as HIV, HBV, HCV, Ebola and Influenza. This paper deals with the global dynamics of generalized virus model with logistic growth rate for target cells, general incidence rate and cellular immunity. The results will be obtained by using Lyapunov's second method and LaSalle's invariance principle. We prove the global stability of the rest points of the system by the value of basic reproduction number (R 0) and the immune response reproduction number (R CTL). We have found that if R 0 < 1 , then the infection-free equilibrium is globally asymptotically stable. For R 0 > 1 and R CTL < 1 , under certain conditions on incidence rate function, immune-free equilibrium is globally asymptotically stable. Finally, we prove that if R 0 > 1 and R CTL > 1 , then under certain conditions on incidence rate function the endemic equilibrium is globally asymptotically stable. Since the logistic growth rate for target cells and general incidence rate have been included in this manuscript, our obtained results are the generalization of those in the previous literatures. Moreover, the results have been obtained with weaker assumptions in comparison with the previous ones. Numerical simulations are presented to support and illustrate our analytical results. [ABSTRACT FROM AUTHOR]

Malaria, a parasite based infectious disease spread by anopheles mosquitos, is widespread, affecting people of all ages. Malaria blood-borne pathogens cause approximately 110 million clinical cases of malaria and between one and two million deaths associated with Plasmodium falciparum each year worldwide, including Bangladesh. In this paper, we develop a human–mosquito transmission dynamics malaria model and analyse of the system properties and solutions. Both analytical and numerical results suggest that if the basic reproduction number R 0 < 1 , the disease-free equilibrium is asymptotically stable, meaning malaria naturally dies out. Further, if R 0 > 1 , the malaria disease persists in the population. We also provide the model calibration to estimate parameters with year-wise malaria incidence data from 2001 to 2014 in Bangladesh. Sensitivity analysis also performs to identify the most critical parameters through the partial rank correlation coefficient method. We found that the contact rate of both humans and mosquitoes had the most extensive influence on malaria prevalence. Finally, the impacts of progression rate, disease-related death rate, recovery rate and the rate of losing immunity are examined through numerical simulations and graphical analysis. [ABSTRACT FROM AUTHOR]

In this paper, we present a stochastic hepatitis B virus (HBV) infection model and the dynamic behaviors of the model are investigated. When the fraction of vertical transmission μ ω ν C is not considered to be new infections, the existence and ergodicity of the stationary distribution of the model are obtained by constructing a suitable Lyapunov function, which determines a critical value ρ 0 s corresponding to the basic reproduction number of ODE system. This implies the persistence of the diseases when ρ 0 s > 1. Meanwhile, the sufficient conditions for the extinction of the diseases are derived when ρ 0 T < 0. What is more, we give the specific expression of the probability density function of the stochastic model around the unique endemic quasi-equilibrium by solving the Fokker–Planck equation. Finally, the numerical simulations are illustrated to verify the theoretical results and match the HBV epidemic data in China. • A stochastic HBV infection model is proposed and studied. • Existence and ergodicity of stationary distribution are proved. • Critical value ρ 0 s corresponding to basic reproduction number ρ 0 is obtained. • Density function of stochastic model near quasi-equilibrium is given. • Simulations match the HBV epidemic data in China. [ABSTRACT FROM AUTHOR]

In this paper, we study a Susceptible–Vaccinated–Infected–Recovered (SVIR) epidemic model in a spatially heterogeneous environment under the Dirichlet boundary condition. We define the basic reproduction number ℜ 0 by the spectral radius of the next generation operator, and show that it is a threshold parameter. The disease extinction and persistence in the case of a bounded domain are considered. More precisely, we show that the disease-free equilibrium is globally asymptotically stable if ℜ 0 < 1 ; the system is uniformly persistent and an endemic equilibrium exists if ℜ 0 > 1. To verify our theoretical results, we perform some numerical simulations, using the Fredholm discretization method to identify ℜ 0. [ABSTRACT FROM AUTHOR]

In this paper, we study a wide spectrum of dynamical features of a prey–predator model with infection in prey population only. In the model formulation, we consider nonlinear incidence for infection transmission and Holling type II as response function of predator. We analyze the model for local stability and Hopf bifurcation, and the theoretical results are validated and extrapolated by numerical simulations. Also, we perform sensitivity analysis to explore the significance of the crucial parameters influencing the densities of prey and predator populations. Our numerical results show that disease persists in the system even if the basic reproduction number is below unity. The rates of predation on susceptible and infected prey populations are shown to dramatically change the behavior of eco-epidemiological system. We extend our model by considering the fact that the newly infected prey becomes productively infectious after the effective contact between susceptible and infectious preys, and some time lag is involved in this biological process; also the conversion process conceals some time. We analyze our eco-epidemiological model with two time delays (incubation delay and predator's gestation delay) for stability and bifurcation. From numerical simulations, we observe that both the delay parameters substantially affect the stable configuration of the system. [ABSTRACT FROM AUTHOR]

This paper aims to explore the behavior of malware propagation on mobile wireless sensor networks (MWSNs). A new malware propagation model with nonlinear incidence rate and sigmoid type removal rate is established, and its global stability, spatiotemporal stability, and optimal control are analyzed. Specifically, the theoretical analysis shows that (i) a forward transcritical bifurcation occurs when the basic reproduction number R 0 > 1 ; (ii) time and space affect the spreading behavior of malware due to spatial distribution; (iii) the optimization technology can effectively control the malware spreading on MWSNs. Finally, some numerical simulations are performed to verify the obtained theoretical results, and the experimental results confirm that the generated patterns are consistent with the field observations of actual MWSNs. Our study helps in controlling the propagation of malware and applicable to design and prediction of the security and robustness of a sensor network. • A new malware propagation model with nonlinear incidence rate and sigmoid type removal rate is studied. • Global stability, spatiotemporal stability, and optimal control are analyzed. • Optimal control technique is employed to reduce the malware propagation. • Stability switching phenomena are obtained via Hopf bifurcation. • Spatio-temporal dynamics depends on transmission rate, time movement of nodes and its initial deployment. [ABSTRACT FROM AUTHOR]

In this paper, a fractional-order model for HIV with drug-resistance and CTL immune response is established. Two cases (subsystem with drug-sensitive and subsystem with drug-resistant) are considered. For both subsystems: firstly, the existence and uniqueness of the positive solution is proved; secondly, the sufficient conditions for the stability of the disease-free equilibrium are obtained; finally, some numerical simulations are performed to verify the theoretical results. After that, the main system is analyzed in a similar way. Calculation indicates that the basic reproduction number of the main system is the maximum value of the basic reproduction numbers of the corresponding subsystems. In addition, through numerical simulation, we know that the drug efficacy plays an important role in the treatment of HIV. • A fractional-order model for HIV with drug-resistance and CTL immune response is constructed. • The basic reproduction number of the main model is the maximum value of the corresponding two subsystems. • Through numerical simulations, the relationship of basic reproduction number with respect to fractional order was found. [ABSTRACT FROM AUTHOR]

In this paper, a new SIS (susceptible–infected–susceptible) epidemic model on complex networks with an infective medium is proposed. The infection rate is modified by applying the theory of probability. By using mean-field approximation, iterative analysis method and mathematical analysis, the epidemic threshold, stabilities of the disease-free equilibrium and the endemic equilibrium are studied. Moreover, some disease control strategies are proposed. The results show that the epidemic threshold plays an important role in the spread of disease. Finally, the theoretical results are confirmed by some simple numerical examples. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to develop and analyze a mathematical model that represents the problem of unemployment in poor countries with limited availability of jobs. We are interested in studying the effect of training programs on the model's dynamics. These training programs aim to improve the skills of unemployed people, contributing to a reduction of the unemployment rate. The model consists of a system of four ordinary differential equations; two equilibria of the model are found: one of which is the employment free equilibrium and the other corresponds to the presence of employment. The existence and stability analysis of both equilibria depend on the basic reproduction number which is found using the method of next generation matrix. However, this number depends on the model parameters which are usually unknown. Hence, we propose to estimate them using the modulating function-based method. Moreover, we study the existence of transcritical bifurcation with the rate of training as a bifurcation parameter. Finally, we support our qualitative results using numerical simulations. [ABSTRACT FROM AUTHOR]

In this paper, we consider a fully discretization scheme for infinite age-structured population models with time-variable fertility rate and mortality rate. Based on the characteristics, the classical linear θ -methods with a kind of two-layer boundary condition are constructed for preserving an invariance of total populations. We are interested in the finite-time convergence and the stability for a long time. With the classical approach, some conjecture on the first order convergence is proved. For the time-independent model the numerical stability is studied by an embedded infinite dimensional dynamical system, which provides a numerical basic reproduction number by the infinite Leslie operator. Furthermore, it is shown that the numerical solutions replicate the un-stability and stability of the analytical solutions for small stepsize. Finally, three examples are given to verify the feasibility of our methods. [ABSTRACT FROM AUTHOR]

Considering the individual differences, spatial environment and the temporary acquired immunity, a general multi-group reaction–diffusion epidemic model with nonlinear incidence and temporary acquired immunity is proposed in this paper. The well-posedness of the solution including the existence of global solutions and the ultimate boundedness of the solutions are obtained, and then we define the basic reproduction number R 0. Further, the threshold dynamics of the disease are obtained in terms of R 0. Moreover, by constructing suitable Lyapunov functions, we obtain the endemic steady state is globally asymptotically stable in homogeneous space and heterogeneous case when R 0 > 1. Based on theoretical analysis, we conclude that the existence of immunity loss rate and the difference of diffusion rate may bring great difficulties to control the disease. Finally, we find the spatial heterogeneity cannot always enhance the infectious risk of the disease and simply increasing the diffusion coefficient cannot effectively control the spread of the disease via some numerical simulations. [ABSTRACT FROM AUTHOR]

A mathematical model for the CD8+ T-cell response to Human T cell leukemia/lymphoma virus type I (HTLV-I) infection is investigated in this paper. The proposed model, which involves four coupled nonlinear ordinary differential equations, describes the interaction of uninfected CD4+T cells, latently infected CD4+T cells, actively infected CD4+T cells and HTLV-I specific cytotoxic T-lymphocytes (CTLs). Our model exhibits three biologically feasible equilibria, namely infection-free steady state, HTLV-I free steady state and an endemic steady state. Our mathematical analysis establishes that the local and global dynamics are determined by the two threshold parameters R 0 and R 1 , basic reproduction number for HTLV-I viral infection and for CTL response, respectively. For R 0 < 1 , the infection-free steady state E 0 is globally asymptotically stable, and HTLV-I viruses are cleared. For R 1 ≤ 1 < R 0 , the HTLV-I free singular point E 1 is globally asymptotically stable, and the HTLV-I infection becomes chronic but no CTL response can be established, and most of the HTLV-I infected individual remains as an asymptomatic carrier. Mathematical analysis shows that a unique endemic steady state E ∗ is globally asymptotically stable for R 1 > 1 in the interior of the feasible region. We perform the sensitivity analysis to find out the key parameters of the HTLV-I infection model with respect to R 0 and R 1. Implications of our findings to the dynamics of CTL response to HTLV-I infections in vivo and pathogenesis of HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP) are discussed. • We investigate a model for HTLV-I infection with CTL response. • Local and global dynamics are determined by the threshold parameters R 0 and R 1. • For R 1 ≤ 1 < R 0 , E 1 is globally asymptotically stable and HTLV-I infection becomes chronic. • Performed global asymptotic stability for E ∗ using Lyapunov function and by geometric approach. • Sensitivity analysis has been done with respect to R 0 and R 1. [ABSTRACT FROM AUTHOR]

In this paper, we consider the dynamics of a plant disease model with a ratio-dependent state impulsive control strategy. It is shown that the boundary equilibrium point of the controlled system is globally asymptotically stable. By combining LaSalle's invariant theorem, Brouwer's fixed point theorem and some analysis techniques, we are able to determine the basic reproduction number, confirm the well-posedness of the model, describe the structure of possible equilibria as well as establish the stability of the equilibria. Most interestingly, we find that in the case that the basic reproduction number is more than unity and the endemic equilibrium locates above the impulsive control strategy, we can obtain a unique k-order periodic solution and the critical values between 1-order and 2-order periodic solutions. Furthermore, it is found that the endemic equilibrium point is also globally asymptotically stable under the control strategy. Finally, we present a numerical example to substantiate the effectiveness of the theoretical results. [ABSTRACT FROM AUTHOR]

We investigate the global asymptotic stabilities of disease-free equilibrium and endemic equilibrium of the deterministic susceptible–exposed–infected–recovered epidemic model (short for SEIR model). The basic reproduction number R 0 , depends on constant contact rate β and natural death rate d and other parameters as well, indicates the critical value of stability, and completely determines the dynamical behavior of the deterministic model. After taking the perturbations of the environments into account, the corresponding stochastic SEIR model with generalized nonlinear incidence is discussed in existence and uniqueness, the extinction in the mean, and the existence of the unique stationary distribution as well. As a consequence, we carry out several numerical simulations to support the main theoretical results of this paper. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the threshold R v S of a stochastic SIS epidemic model with partially protective vaccination of efficacy e ∈ [ 0 , 1 ] . Firstly, we show that there exists a unique global positive solution of the stochastic system. Then R v S > 1 is verified to be sufficient for persistence in the mean of the system. Furthermore, three conditions for the disease to die out are given, which improve the previously-known results on extinction of the disease. We also obtain that large noise will exponentially suppress the disease from persisting regardless of the value of the basic reproduction number R v S . [ABSTRACT FROM AUTHOR]

In this paper, a within-host chikungunya virus infection model with two delays is considered. The basic reproductive number R 0 is formulated. If R 0 < 1 , the virus-free equilibrium is globally asymptotically stable and the disease always dies out. If R 0 > 1 , the global stability of the unique endemic equilibrium E 1 is proved for the case without the time delay of antigenic stimulation, which can change the stability of E 1 and lead to the existence of Hopf bifurcation. Furthermore, explicit formulae for determining the direction of Hopf bifurcation and the stability of bifurcating periodic solutions are established. Finally, some numerical simulations are presented to illustrate the results. [ABSTRACT FROM AUTHOR]

In this paper, we deal with the global dynamics of a two-strain flu model with delay. Using the method of Lyapunov functional, we show that if the basic reproduction number is less than one, then both strains die out; but when the number is larger than one, one or both of the strains become endemic. The main results are confirmed by some numerical simulations. The theoretical results obtained here provide some useful information on the impact of the vaccination rate of a single vaccine for one strain on the dynamics of the two strains. [ABSTRACT FROM AUTHOR]