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Modeling Virus Dynamics in Time and Space
Published in Ranjit Kumar Upadhyay, Satteluri R. K. Iyengar, Spatial Dynamics and Pattern Formation in Biological Populations, 2021
Ranjit Kumar Upadhyay, Satteluri R. K. Iyengar
Spatial heterogeneity: It is generally defined as the complexity and variability of the system variables in space. It is a challenge to study how spatial heterogeneity of the environment and movement of individuals have an impact on the persistence and extinction of a species/disease. To understand the impact of spatial heterogeneity of the environment and movement of individuals on the persistence and extinction of a disease, Allen et al. [5] proposed a frequency-dependent SIS reaction-diffusion model for a population in a continuous spatial habitat. When we consider spatially heterogeneous interventions, it is essential to represent the location of hosts and the pattern of transmission. The spatial heterogeneities of intervention add another layer of complexity to the system and provide a challenge for modeling [223]. Examples of spatially localized interventions include ring culling (as carried out in 2001 UK foot and mouth epidemic [135] and ring vaccination [264]), school closure [120], and local top-up vaccination campaigns. Every intervention is in some sense local and therefore spatially heterogeneous.
Disease outbreaks
Published in Ian Scoones, Andy Stirling, The Politics of Uncertainty, 2020
Hayley MacGregor, Santiago Ripoll, Melissa Leach
Even more importantly, the uncertainty of chronic conflict has permeated people’s everyday lives. Under continuous threat of physical violence, people seek to prioritise the immediate need for physical security over Ebola-related activities. An example of this was the ‘Ebola strike’ that occurred in October 2018, when many community members halted Ebola activities in protest at the lack of security. An historical political marginalisation vis-à-vis a central government that is also unable to protect people generates distrust of health services and enables plausible explanations of Ebola as a government plot. Conventional methods of case management – listing contacts – become fraught with difficulty, as fear and mistrust towards the response make the act of giving that information highly risky. As the main method of the Ebola vaccine on trial was ring vaccination, the incompleteness of these lists of contacts had an important impact on the efficacy of vaccination. For much of the response, the number of Ebola deaths at home (rather than in treatment centres) of people who were not on the case management contact list was high, reaching up to a third of cases (WHO 2019b). In addition, Congolese citizens wonder why Ebola is prioritised over other health priorities in an already limited health system. In turn, this mistrust is exacerbated by the disruptive Ebola economy, and the unequal access to finance and resources that have accompanied the response among fragmented local political authorities. Thus, the roll-out of the response has inevitably generated a new set of deep uncertainties between local socio-political dynamics and response activities.
A systematic review of mathematical models of the Ebola virus disease
Published in International Journal of Modelling and Simulation, 2022
Suliman Jamiel M. Abdalla, Faraimunashe Chirove, Keshlan S. Govinder
The impact of ring, mass, and voluntary vaccination strategies were explored, and valuable insights were provided. Brettin et al [97]. concluded that a voluntary vaccination might be able to eradicate EVD, particularly when added to other control measures. Nguyen et al [46]. found that mass vaccination of 85% coverage can eradicate the disease if it was launched between five months before and one week after the outbreak. Merler et al [93]. concluded that a ring vaccination to be effective in containing an epidemic up to the value of R0 = 1.6 This figure was increased when other control measures were added. Kucharski et al [94]. found that when an epidemic is less severe, a ring vaccination could eradicate the outbreak. Camacho et al [88]. suggested that when a vaccination trial was started at an earlier time, the probability of eliminating the disease in vaccinated groups increased. The studies [88,94,97], however, contained some limitations. Brettin et al [97]. assumed the population to be rational enough to decide to be vaccinated voluntarily and assumed the population to be well informed about the risk of the disease and the direct and indirect cost of vaccinations. Kucharski et al [94]. did not account for different possible immunity periods that the Merck rVSV-ZEBOV vaccine might have [105]. Camacho et al [88]. did not account for any logistical constraints that may affect the feasibility of the vaccination trial in the studied areas.
Risk-averse multi-stage stochastic programming to optimizing vaccine allocation and treatment logistics for effective epidemic response
Published in IISE Transactions on Healthcare Systems Engineering, 2022
Xuecheng Yin, İ Esra Büyüktahtakın
Due to the high death rate and difficulties in Ebola treatment, new vaccinations have been developed and widely used to help control the disease. Various studies considered vaccination as a strategy and involved the uncertainty of the supply of vaccines. For instance, Kelly et al. (2019) used a stochastic branching process model to project the size and duration of the 2018–2019 Ebola outbreak in the Democratic Republic of Congo (DRC) under high (62%), low (44%), and zero (0%) estimates of vaccination coverage. Xie (2019) modified the Susceptible-Exposed-Infective-Hospitalized-Funeral-Removed model of Legrand et al. (2007) to examine disease transmission dynamics after vaccination for the 2014 Ebola outbreak in Liberia and found that the ring vaccination strategy would reduce the transmission rate. Chowell et al. (2019) employed an individual-level stochastic transmission model to evaluate ring and community vaccination strategies for the 2018–2019 DRC Ebola transmission. Their results also indicated that a ring vaccination strategy could speed up and enhance the probability of epidemic containment. Brettin et al. (2018) constructed a game-theoretic model of the EVD incorporating individual decisions on vaccination to study the effect of a promising Ebola vaccine (rVSV-ZEBOV). Their result showed that Ebola could be eradicated if voluntary vaccination programs are coupled with focused public education efforts.