scholarly journals Modeling and reviewing analysis of the COVID-19 epidemic in Algeria with diagnostic shadow

2021 ◽  
Author(s):  
Jiwei Jia ◽  
Siyu Liu ◽  
Yawen Liu ◽  
Ruitong Shan ◽  
Khaled Zennir ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Reproduction Number ◽  
Control Strategies ◽  
Control Measures ◽  
Effective Control ◽  
Reproduction Numbers ◽  
Epidemic Dynamic ◽  
Reported Data ◽  
Parameter Values ◽  
Research Period

In this paper, we formulate a special epidemic dynamic model to describe the transmission of COVID-19 in Algeria. We derive the threshold parameter control reproduction number (R0c ), and present the effective control reproduction number (Rc(t)) as a real-time index for evaluating the epidemic under different control strategies. Due to the limitation of the reported data, we redefine the number of accumulative confirmed cases with diagnostic shadow and then use the processed data to do the optimal numerical simulations. According to the control measures, we divide the whole research period into six stages. And then the corresponding medical resource estimations and the average effective control reproduction numbers for each stage are given. Meanwhile, we use the parameter values which are obtained from the optimal numerical simulations to forecast the whole epidemic tendency under different control strategies.

scholarly journals Modelling, Simulations and Analysis of the First and Second COVID-19 Epidemics in Beijing

2021 ◽  
Author(s):  
Lequan Min
Keyword(s):  
Numerical Simulations ◽  
Prevention And Control ◽  
Control Strategies ◽  
Equation Model ◽  
Control Measures ◽  
Disease Spreading ◽  
Prevention And Control Measures ◽  
Asymptomatic Individuals ◽  
Reported Data ◽  
And Control

AbstractTo date, over 130 million people on infected with COVID-19. It causes more 2.8 millions deaths. This paper introduces a symptomatic-asymptomatic-recoverer-dead differential equation model (SARDDE). It gives the conditions of the asymptotical stability on the disease-free equilibrium of SARDDE. It proposes the necessary conditions of disease spreading for the SARDDE. Based on the reported data of the first and the second COVID-19 epidemics in Beijing and simulations, it determines the parameters of SARDDE, respectively. Numerical simulations of SARDDE describe well the outcomes of current symptomatic and asymptomatic individuals, recovered symptomatic and asymptomatic individuals, and died individuals, respectively. The numerical simulations suggest that both symptomatic and asymptomatic individuals cause lesser asymptomatic spread than symptomatic spread; blocking rate of about 90% cannot prevent the spread of the COVID19 epidemic in Beijing; the strict prevention and control strategies implemented by Beijing government is not only very effective but also completely necessary. The numerical simulations suggest also that using the data from the beginning to the day after about two weeks at the turning point can estimate well or approximately the following outcomes of the two COVID-19 academics, respectively. It is expected that the research can provide better understanding, explaining, and dominating for epidemic spreads, prevention and control measures.

scholarly journals Modelling, Simulations and Analysis of the First and Second COVID-19 Epidemics in Beijing

2021 ◽  
Author(s):  
Lequan Min
Keyword(s):  
Numerical Simulations ◽  
Prevention And Control ◽  
Control Strategies ◽  
Equation Model ◽  
Control Measures ◽  
Virtual Simulations ◽  
Prevention And Control Measures ◽  
Asymptomatic Individuals ◽  
Reported Data ◽  
And Control

To date, over 182 million people on infected with COVID-19. It causes more 3.9 millions deaths. This paper introduces a symptomatic-asymptomatic-recoverer-dead differential equation model (SARDDE). It gives the conditions of the asymptotical stability on the disease-free equilibrium of SARDDE. It proposes the necessary conditions of disease spreading for the SARDDE. Based on the reported data of the first and the second COVID-19 epidemics in Beijing and simulations, it determines the parameters of SARDDE, respectively. Numerical simulations of SARDDE describe well the outcomes of current symptomatic and asymptomatic individuals, recovered symptomatic and asymptomatic individuals, and died individuals, respectively. The numerical simulations suggest that both symptomatic and asymptomatic individuals cause lesser asymptomatic spread than symptomatic spread; the blocking rates of about 80% and 97.5% to the symptomatic individuals cannot prevent the spread of the first and second COVID19 epidemics in Beijing, respectively. Virtual simulations suggest that the strict prevention and control strategies implemented by Beijing government are not only very effective but also completely necessary. The numerical simulations suggest also that using the data from the beginning to the day after about 14 -- 17 days at the turning point can estimate well the following outcomes of the two COVID-19 academics, respectively. It is expected that the research can provide better understanding, explaining, and dominating for epidemic spreads, prevention and control measures.

scholarly journals Cost effective reproduction number based strategies for reducing deaths from COVID-19

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Christopher Thron ◽  
Vianney Mbazumutima ◽  
Luis V. Tamayo ◽  
Léonard Todjihounde
Keyword(s):  
High Risk ◽  
Reproduction Number ◽  
Control Strategies ◽  
Cost Model ◽  
Cost Effective ◽  
Control Measures ◽  
Effective Control ◽  
Target Value ◽  
Heuristic Strategies ◽  
Implementation Costs

AbstractIn epidemiology, the effective reproduction number $R_{e}$ R e is used to characterize the growth rate of an epidemic outbreak. If $R_{e} >1$ R e > 1 , the epidemic worsens, and if $R_{e}< 1$ R e < 1 , then it subsides and eventually dies out. In this paper, we investigate properties of $R_{e}$ R e for a modified SEIR model of COVID-19 in the city of Houston, TX USA, in which the population is divided into low-risk and high-risk subpopulations. The response of $R_{e}$ R e to two types of control measures (testing and distancing) applied to the two different subpopulations is characterized. A nonlinear cost model is used for control measures, to include the effects of diminishing returns. Lowest-cost control combinations for reducing instantaneous $R_{e}$ R e to a given value are computed. We propose three types of heuristic strategies for mitigating COVID-19 that are targeted at reducing $R_{e}$ R e , and we exhibit the tradeoffs between strategy implementation costs and number of deaths. We also consider two variants of each type of strategy: basic strategies, which consider only the effects of controls on $R_{e}$ R e , without regard to subpopulation; and high-risk prioritizing strategies, which maximize control of the high-risk subpopulation. Results showed that of the three heuristic strategy types, the most cost-effective involved setting a target value for $R_{e}$ R e and applying sufficient controls to attain that target value. This heuristic led to strategies that begin with strict distancing of the entire population, later followed by increased testing. Strategies that maximize control on high-risk individuals were less cost-effective than basic strategies that emphasize reduction of the rate of spreading of the disease. The model shows that delaying the start of control measures past a certain point greatly worsens strategy outcomes. We conclude that the effective reproduction can be a valuable real-time indicator in determining cost-effective control strategies.

Mathematical analysis of a two-sex Human Papillomavirus (HPV) model

2018 ◽  
Vol 11 (07) ◽  
pp. 1850092 ◽  
Author(s):  
A. Omame ◽  
R. A. Umana ◽  
D. Okuonghae ◽  
S. C. Inyama
Keyword(s):  
Human Papillomavirus ◽  
Numerical Simulations ◽  
Deterministic Model ◽  
Reproduction Number ◽  
Effective Control ◽  
Male Population ◽  
Previous Infection ◽  
Males And Females ◽  
Parameter Values ◽  
The Impact

A two-sex deterministic model for Human Papillomavirus (HPV) that assesses the impact of treatment and vaccination on its transmission dynamics is designed and rigorously analyzed. The model is shown to exhibit the phenomenon of backward bifurcation, caused by the imperfect vaccine as well as the re-infection of individuals who recover from a previous infection, when the associated reproduction number is less than unity. Analysis of the reproduction number reveals that the impact of treatment on effective control of the disease is conditional, and depends on the sign of a certain threshold unlike when preventive measures are implemented (i.e. condom use and vaccination of both males and females). Numerical simulations of the model showed that, based on the parameter values used therein, a vaccine (with 75% efficacy) for male population with about 40% condom compliance by females will result in a significant reduction in the disease burden in the population. Also, the numerical simulations of the model reveal that with 70% condom compliance by the male population, administering female vaccine (with 45% efficacy) is sufficient for effective control of the disease.

scholarly journals COVID-19 Pandemic Outbreak in the Subcontinent: A Data Driven Analysis

2021 ◽  
Vol 11 (9) ◽  
pp. 889
Author(s):  
Bikash Chandra Singh ◽  
Zulfikar Alom ◽  
Haibo Hu ◽  
Mohammad Muntasir Rahman ◽  
Mrinal Kanti Baowaly ◽  
...  
Keyword(s):  
Reproduction Number ◽  
Control Strategies ◽  
Epidemiological Data ◽  
Data Driven ◽  
Effective Control ◽  
Spread Rate ◽  
Wuhan City ◽  
Data Set ◽  
Critical Situation ◽  
Reproduction Numbers

Human civilization is experiencing a critical situation that presents itself for a new coronavirus disease 2019 (COVID-19). This virus emerged in late December 2019 in Wuhan city, Hubei, China. The grim fact of COVID-19 is, it is highly contagious in nature, therefore, spreads rapidly all over the world and causes severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Responding to the severity of COVID-19 research community directs the attention to the analysis of COVID-19, to diminish its antagonistic impact towards society. Numerous studies claim that the subcontinent, i.e., Bangladesh, India, and Pakistan, could remain in the worst affected region by the COVID-19. In order to prevent the spread of COVID-19, it is important to predict the trend of COVID-19 beforehand the planning of effective control strategies. Fundamentally, the idea is to dependably estimate the reproduction number to judge the spread rate of COVID-19 in a particular region. Consequently, this paper uses publicly available epidemiological data of Bangladesh, India, and Pakistan to estimate the reproduction numbers. More specifically, we use various models (for example, susceptible infection recovery (SIR), exponential growth (EG), sequential Bayesian (SB), maximum likelihood (ML) and time dependent (TD)) to estimate the reproduction numbers and observe the model fitness in the corresponding data set. Experimental results show that the reproduction numbers produced by these models are greater than 1.2 (approximately) indicates that COVID-19 is gradually spreading in the subcontinent.

scholarly journals Controlling the Spatial Spread of a Xylella Epidemic

2021 ◽  
Vol 83 (4) ◽  
Author(s):  
Sebastian Aniţa ◽  
Vincenzo Capasso ◽  
Simone Scacchi
Keyword(s):  
Spatial Structure ◽  
Numerical Simulations ◽  
Control Strategies ◽  
Xylella Fastidiosa ◽  
Cost Effective ◽  
Olive Tree ◽  
Control Measures ◽  
Weed Biomass ◽  
Spatial Spread ◽  
Olive Trees

AbstractIn a recent paper by one of the authors and collaborators, motivated by the Olive Quick Decline Syndrome (OQDS) outbreak, which has been ongoing in Southern Italy since 2013, a simple epidemiological model describing this epidemic was presented. Beside the bacterium Xylella fastidiosa, the main players considered in the model are its insect vectors, Philaenus spumarius, and the host plants (olive trees and weeds) of the insects and of the bacterium. The model was based on a system of ordinary differential equations, the analysis of which provided interesting results about possible equilibria of the epidemic system and guidelines for its numerical simulations. Although the model presented there was mathematically rather simplified, its analysis has highlighted threshold parameters that could be the target of control strategies within an integrated pest management framework, not requiring the removal of the productive resource represented by the olive trees. Indeed, numerical simulations support the outcomes of the mathematical analysis, according to which the removal of a suitable amount of weed biomass (reservoir of Xylella fastidiosa) from olive orchards and surrounding areas resulted in the most efficient strategy to control the spread of the OQDS. In addition, as expected, the adoption of more resistant olive tree cultivars has been shown to be a good strategy, though less cost-effective, in controlling the pathogen. In this paper for a more realistic description and a clearer interpretation of the proposed control measures, a spatial structure of the epidemic system has been included, but, in order to keep mathematical technicalities to a minimum, only two players have been described in a dynamical way, trees and insects, while the weed biomass is taken to be a given quantity. The control measures have been introduced only on a subregion of the whole habitat, in order to contain costs of intervention. We show that such a practice can lead to the eradication of an epidemic outbreak. Numerical simulations confirm both the results of the previous paper and the theoretical results of the model with a spatial structure, though subject to regional control only.

Quantitative Risk Assessment of Listeriosis-Associated Deaths Due to Listeria monocytogenes Contamination of Deli Meats Originating from Manufacture and Retail

2010 ◽  
Vol 73 (4) ◽  
pp. 620-630 ◽  
Author(s):  
ABANI K. PRADHAN ◽  
RENATA IVANEK ◽  
YRJÖ T. GRÖHN ◽  
ROBERT BUKOWSKI ◽  
IFIGENIA GEORNARAS ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Listeria Monocytogenes ◽  
Relative Risk ◽  
Storage Temperature ◽  
Control Strategies ◽  
Quantitative Risk Assessment ◽  
Sensitivity Analyses ◽  
Effective Control ◽  
Lag Phase ◽  
Reported Data

The objective of this study was to estimate the relative risk of listeriosis-associated deaths attributable to Listeria monocytogenes contamination in ham and turkey formulated without and with growth inhibitors (GIs). Two contamination scenarios were investigated: (i) prepackaged deli meats with contamination originating solely from manufacture at a frequency of 0.4% (based on reported data) and (ii) retail-sliced deli meats with contamination originating solely from retail at a frequency of 2.3% (based on reported data). Using a manufacture-to-consumption risk assessment with product-specific growth kinetic parameters (i.e., lag phase and exponential growth rate), reformulation with GIs was estimated to reduce human listeriosis deaths linked to ham and turkey by 2.8- and 9-fold, respectively, when contamination originated at manufacture and by 1.9- and 2.8-fold, respectively, for products contaminated at retail. Contamination originating at retail was estimated to account for 76 and 63% of listeriosis deaths caused by ham and turkey, respectively, when all products were formulated without GIs and for 83 and 84% of listeriosis deaths caused by ham and turkey, respectively, when all products were formulated with GIs. Sensitivity analyses indicated that storage temperature was the most important factor affecting the estimation of per annum relative risk. Scenario analyses suggested that reducing storage temperature in home refrigerators to consistently below 7°C would greatly reduce the risk of human listeriosis deaths, whereas reducing storage time appeared to be less effective. Overall, our data indicate a critical need for further development and implementation of effective control strategies to reduce L. monocytogenes contamination at the retail level.

scholarly journals Transmission Dynamics of Lymphatic Filariasis: A Mathematical Approach

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
C. P. Bhunu ◽  
S. Mushayabasa
Keyword(s):  
Numerical Simulations ◽  
Lymphatic Filariasis ◽  
Reproduction Number ◽  
Epidemiological Model ◽  
Transmission Dynamics ◽  
Effective Control ◽  
Mathematical Approach

An epidemiological model for the spread of lymphatic filariasis, a mosquito-borne infection, is developed and analysed. The epidemic thresholds known as the reproduction number and equilibria for the model are determined and stabilities analysed. Results from the analysis of the reproduction number suggest that treatment will somehow contribute to a reduction in lymphatic filariasis cases, but what it does not show is the magnitude of the reduction, a part answered by the numerical simulations. Numerical simulations show that even when all lymphatic filariasis cases displaying elephantiasis symptoms are put on treatment it will not be able to eradicate the disease. This result suggests that effective control of lymphatic filariasis may lie in treatment for those displaying symptoms as well as chemoprophylaxis for the exposed.

An experimental evaluation of conventional control measures against the sheep tick, Ixodes ricinus (L.) (Acari: Ixodidae). II. The dynamics of the tick-host interaction

1985 ◽  
Vol 75 (3) ◽  
pp. 501-518 ◽  
Author(s):  
Sarah E. Randolph ◽  
Gordon M. Steele
Keyword(s):  
Ixodes Ricinus ◽  
Control Method ◽  
Control Strategies ◽  
Stocking Density ◽  
Experimental Manipulation ◽  
Control Measures ◽  
Effective Control ◽  
Contact Rate ◽  
Host Interaction ◽  
Questing Ticks

AbstractThe experimental manipulation of separate, but originally identical, populations of Ixodes ricinus (L.) by applying three conventional tick control measures in different enclosures on naturally infested moorland in Wales allowed the elements of the tick-host interaction to be analysed quantitatively and the effectiveness of the control methods to be compared. From the relationship between the sheep stocking density and the numbers of questing ticks picked up by fortnightly blanket-dragging in each enclosure, the death rate of ticks during their activity season and the rate of contact between sheep and ticks were calculated. From this, it was possible to investigate the effect of different stocking densities on the feeding success of ticks. A major factor determining the much lower contact rate for larvae than for nymphs was the different spatial distribution of questing ticks, clumped for larvae and random for nymphs. The non-random use by sheep of the three different vegetation zones in the paddock resulted in the highest contact rate between sheep and ticks in the pasture area, but tick survival was apparently highest in the bog area. Combining these factors resulted in the prediction that the bracken area was the least favourable habitat for ticks. In the two enclosures where the sheep were not treated with acaricide the mean tick loads on the sheep were similar, but the lower overall use of the pasture by the sheep in the low stocking density enclosure (2/ha) resulted in slightly lower tick loads there compared with those in the high stocking density enclosure (4/ha). The numbers of ticks counted in the second year showed that pasture spelling was the most effective control method, acaricide treatment was less effective, and the benefits of halving the stocking density were marginal. The implications of these results for control strategies are discussed.

scholarly journals Modelling the Effectiveness of Epidemic Control Measures in Preventing the Transmission of COVID-19 in Malaysia

2020 ◽  
Vol 17 (15) ◽  
pp. 5509 ◽  
Author(s):  
Balvinder Singh Gill ◽  
Vivek Jason Jayaraj ◽  
Sarbhan Singh ◽  
Sumarni Mohd Ghazali ◽  
Yoon Ling Cheong ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Model Calibration ◽  
Reproduction Number ◽  
Close Contact ◽  
Movement Control ◽  
Control Measures ◽  
Seir Model ◽  
Epidemic Curve ◽  
Reproduction Numbers ◽  
Control Order

Malaysia is currently facing an outbreak of COVID-19. We aim to present the first study in Malaysia to report the reproduction numbers and develop a mathematical model forecasting COVID-19 transmission by including isolation, quarantine, and movement control measures. We utilized a susceptible, exposed, infectious, and recovered (SEIR) model by incorporating isolation, quarantine, and movement control order (MCO) taken in Malaysia. The simulations were fitted into the Malaysian COVID-19 active case numbers, allowing approximation of parameters consisting of probability of transmission per contact (β), average number of contacts per day per case (ζ), and proportion of close-contact traced per day (q). The effective reproduction number (Rt) was also determined through this model. Our model calibration estimated that (β), (ζ), and (q) were 0.052, 25 persons, and 0.23, respectively. The (Rt) was estimated to be 1.68. MCO measures reduce the peak number of active COVID-19 cases by 99.1% and reduce (ζ) from 25 (pre-MCO) to 7 (during MCO). The flattening of the epidemic curve was also observed with the implementation of these control measures. We conclude that isolation, quarantine, and MCO measures are essential to break the transmission of COVID-19 in Malaysia.

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