scholarly journals The serial and generation intervals from SARS-CoV-2 transmission dynamics and their potential application in the epidemiology of two citrus diseases

2021 ◽  
Vol 39 (4) ◽  
Author(s):  
Oscar Pérez-Hernández ◽  
Francisco Sautua ◽  
Santiago Domínguez-Monge ◽  
Carlos Cecilio Góngora-Canul ◽  
Marcelo Carmona
Keyword(s):  
Disease Transmission ◽  
Disease Incidence ◽  
Plant Diseases ◽  
Control Measures ◽  
Transmission Dynamics ◽  
Spatial Pattern Analysis ◽  
Transmission Chain ◽  
Citrus Diseases ◽  
Plant Pathosystems ◽  
Tristeza Virus

<p>Since the start of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing the coronavirus disease 2019 (COVID-19) pandemic, the concepts of serial and generation intervals have been used as key epidemiological measures to understand the transmission dynamics of the disease. We carefully examined and repurposed these concepts to the understanding of the transmission chain and dynamics of two major citrus diseases: tristeza virus (caused by Citrus tristeza virus, CTV) and Huanglongbing (caused by <em>Candidatus</em> Liberibacter asiaticus). Following the fundamental definition of the concepts, the review delineates the transmission chain in the SARS-CoV-2 and that of CTV and CLas, pointing out their major similarities and differences. Then, it discusses estimation of the serial and generation intervals and their distributions for both plant diseases. Identification of infector-infectee tree pairs in a transmission chain within orchards is proposed through use of disease incidence data from intensive mapping, spatial pattern analysis, conditional probability, and simulation approaches. Like in SARS-CoV-2 dynamics, pre-symptomatic transmission in these two plant pathosystems is of epidemiological significance. Hence, estimation of the serial and generation interval can lay the foundations to understanding of early disease transmission dynamics, thus the implementation of vector control measures or eradication of infected trees. We hope this review motivates discussions on estimation and usage of these concepts to enhance understanding of the epidemiology of both of the herein examined citrus diseases.</p>

MODELING CHOLERA TRANSMISSION UNDER DISEASE CONTROL MEASURES

2020 ◽  
pp. 1-26
Author(s):  
MARGARET BROWN ◽  
MIKO JIANG ◽  
CHAYU YANG ◽  
JIN WANG
Keyword(s):  
Disease Control ◽  
Disease Transmission ◽  
Control Measures ◽  
Transmission Dynamics ◽  
Threshold Dynamics ◽  
Education Programs ◽  
Multiple Control ◽  
Indirect Transmission ◽  
Transmission Pathways ◽  
The Impact

We present a new mathematical model to investigate the transmission dynamics of cholera under disease control measures that include education programs and water sanitation. The model incorporates the impact of education programs into the disease transmission rates and that of water sanitation into the environmental pathogen dynamics. We conduct a detailed analysis to the autonomous system of the model and establish the local and global stabilities of its equilibria that characterize the threshold dynamics of cholera. We then perform an optimal control study on the general model with time-dependent controls and explore effective approaches to implement the education programs and water sanitation while balancing their costs. Our analysis and simulation highlight the complex interaction among the direct and indirect transmission pathways of the disease, the intrinsic growth of the environmental pathogen and the impact of multiple control measures, and their roles in collectively shaping the transmission dynamics of cholera.

scholarly journals Suitability of the MODIS-NDVI Time-Series for a Posteriori Evaluation of the Citrus Tristeza Virus Epidemic

2020 ◽  
Vol 12 (12) ◽  
pp. 1965
Author(s):  
Daniela Vanella ◽  
Simona Consoli ◽  
Juan Miguel Ramírez-Cuesta ◽  
Matilde Tessitori
Keyword(s):  
Time Series ◽  
Plant Pathogens ◽  
Management Practices ◽  
Citrus Tristeza Virus ◽  
Plant Diseases ◽  
Control Measures ◽  
Ndvi Time Series ◽  
The Impact ◽  
Tristeza Virus ◽  
Citrus Tristeza

The technological advances of remote sensing (RS) have allowed its use in a number of fields of application including plant disease depiction. In this study, an RS approach based on an 18-year (i.e., 2001–2018) time-series analysis of Normalized Difference Vegetation Index (NDVI) data, derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) and processed with TIMESAT free software, was applied in Sicily (insular Italy). The RS approach was carried out in four orchards infected by Citrus tristeza virus (CTV) at different temporal stages and characterized by heterogeneous conditions (e.g., elevation, location, plant age). The temporal analysis allowed the identification of specific metrics of the NDVI time-series at the selected sites during the study period. The most reliable parameter which was able to identify the temporal evolution of CTV syndrome and the impact of operational management practices was the “Base value” (i.e., average NDVI during the growing seasons, which reached R2 values up to 0.88), showing good relationships with “Peak value”, “Small integrated value” and “Amplitude”, with R2 values of 0.63, 0.70 and 0.75, respectively. The approach herein developed is valid to be transferred to regional agencies involved in and/or in charge of the management of plant diseases, especially if it is integrated with ground-based early detection methods or high-resolution RS approaches, in the case of quarantine plant pathogens requiring control measures at large-scale level.

Transmission dynamics and control options for Echinococcus granulosus

Parasitology ◽  
2003 ◽  
Vol 127 (S1) ◽  
pp. S143-S158 ◽  
Author(s):  
P. R. TORGERSON ◽  
D. D. HEATH
Keyword(s):  
Echinococcus Granulosus ◽  
Disease Incidence ◽  
Effective Means ◽  
Public Health Problem ◽  
Control Measures ◽  
Transmission Dynamics ◽  
Effective Control ◽  
Global Public Health ◽  
Persistent Problem ◽  
Economic Output

Cystic echinococcosis, caused by the larval stage of Echinococcus granulosus, is a global public health problem. Whilst in a few localities, such as New Zealand, the parasite has been effectively controlled or even eradicated, in most endemic regions it remains a persistent problem. In some areas, such as the former Soviet Union, the disease incidence in humans has increased rapidly in recent years. It is important to have an understanding of the transmission dynamics, both between dogs and domestic livestock where the parasite maintains itself and from dogs to people. It is from this knowledge that effective control measures can be devised to reduce the prevalence of the parasite in animals and hence reduce the incidence of human disease. Mathematical models to describe the transmission of the parasite and the effects of different control strategies were first proposed over twenty years ago. Since then further information has been acquired, new technology has been developed and better computing technology has become available. In this review, we summarise these developments and put together a theoretical framework on the interpretation of surveillance information, how this affects transmission and how this information can be exploited to develop new intervention strategies for the control of the parasite. In particular, the parasite remains a persistent or re-emerging problem in countries of low economic output where resources for an intensive control programme, that has been successful in rich countries, are not available. By understanding of the transmission biology, including mathematical modelling, alternative and cost-effective means of control can be developed.

scholarly journals Quadmester-wise comparison of disease transmission dynamics of COVID-19 among health care workers in Kannur district, Kerala

2021 ◽  
Vol 8 (5) ◽  
pp. 2481
Author(s):  
Ameena Subair Raheela ◽  
Sajish Chandran ◽  
Deepak Rajan ◽  
Preetha Muduvana
Keyword(s):  
Health Care ◽  
Health Care Workers ◽  
Disease Transmission ◽  
Local Level ◽  
Control Measures ◽  
Transmission Dynamics ◽  
Work Place ◽  
Cross Sectional ◽  
Indirect Contact ◽  
Care Workers

Background: Health-care workers (HCWs) may get infected by direct or indirect contact with infected patients or other HCWs or from the community as well, depending on the phase through which pandemic progresses. Knowledge about the disease transmission dynamics as the pandemic advances is a need so that appropriate monitoring, prevention and control measures for HCWs can be implemented at local level. The main objective of this study was quadmester-wise comparison of disease transmission dynamics of COVID-19 among HCWs in Kannur district.Methods: A cross-sectional study was carried out among HCWs reported positive for SARS-CoV-2 in Kannur district, Kerala. COVID-19 positive HCWs reported in the district were consolidated and contacted over phone and details were collected using a semi-structured questionnaire. Data were entered into microsoft excel and analysed using statistical package for social sciences (SPSS) trial version. Chi-square test was used to compare differences observed in the two groups and binary logistic regression was done to pick out the significant predictors of variability in disease transmission among the two groups.Results: Total respondents in the first and second quadmester were 243 and 1665, respectively. Factors like gender, clinical features, source of infection, family as source and type of duty taken were found to be statistically significant for the disease transmission dynamics among HCWs.Conclusions: As the pandemic advances, irrespective of the type of work place, self-reporting and regular testing of HCWs will help to check HCWs from getting infected and spreading the disease.

scholarly journals Citrus Diseases Exotic to Florida: Citrus Tristeza Virus– Stem Pitting (CTV-SP)

EDIS ◽  
2006 ◽  
Vol 2006 (7) ◽  
Author(s):  
Kuang-Ren Chung ◽  
Ronald H. Brlansky
Keyword(s):  
Citrus Tristeza Virus ◽  
Plant Diseases ◽  
Production Costs ◽  
Brown Spot ◽  
Economic Losses ◽  
Citrus Diseases ◽  
Florida Citrus ◽  
Tristeza Virus ◽  
Stem Pitting ◽  
Citrus Tristeza

Citrus is susceptible to a large number of diseases caused by plant pathogens. Economic losses due to plant diseases can be severe, but fortunately, not all pathogens attacking citrus are present in Florida. Major citrus diseases currently present in Florida include: Alternaria brown spot, blight, citrus canker, greasy spot, melanose, Phytophthora-induced diseases (foot and root rot, brown rot), postbloom fruit drop (PFD), scab, and tristeza. An exotic, destructive disease called citrus greening (Huanglongbing) has recently been found in Florida. Any exotic diseases, if introduced, will increase production costs and decrease profitability for Florida growers. Exotic diseases affect the viability of the industry or the varieties that could be profitably grown. Background information for each exotic citrus disease will be presented in a series of fact sheets to: 1) provide a basis for evaluating exotic pathogens that may pose potential risks to Florida citrus; and 2) create a decision-making framework to prevent their introduction and spread. This paper will discuss Citrus tristeza virus-Stem Pitting (CTV-SP) disease. This article is written based on the materials used for the Workshops of the Exotic Citrus Pathogen Threat Project led by Drs. S. M. Garnsey and H. W. Browning, and approved for publication.

scholarly journals Reconstruction of the transmission dynamics of the first COVID-19 epidemic wave in Thailand

2021 ◽  
Author(s):  
Chaiwat Wilasang ◽  
Natcha Jitsuk ◽  
Chayanin Sararat ◽  
Charin Modchang
Keyword(s):  
Disease Transmission ◽  
Infected Individual ◽  
Mainland China ◽  
Stochastic Modelling ◽  
Epidemiological Data ◽  
Control Measures ◽  
Transmission Dynamics ◽  
Thai Government ◽  
And Control ◽  
Epidemic Wave

Abstract Thailand was the first country reporting the first Coronavirus disease 2019 (COVID-19) infected individual outside mainland China. Here we delineated the course of the COVID-19 outbreak together with the timeline of the control measures and public health policies employed by the Thai government during the first wave of the COVID-19 outbreak in Thailand. Based on the comprehensive epidemiological data, we reconstructed the dynamics of COVID-19 transmission in Thailand using a stochastic modelling approach. Our stochastic model incorporated effects of individual heterogeneity in infectiousness on the disease transmission, which allows us to capture relevant features of superspreading events. We found that our model could accurately capture the transmission dynamics of the first COVID-19 epidemic wave in Thailand. The model predicted that at the end of the first wave, the number of cumulative confirmed cases was 3,091 (95%CI: 2,782 - 3,400). We also estimated the time-varying reproduction number (Rt) during the first epidemic wave. We found that after implementing the nationwide interventions, the Rt in Thailand decreased from the peak value of 5.67 to a value below one in less than one month, indicating that the control measures employed by the Thai government during the first COVID-19 epidemic wave were effective. Finally, effects of transmission heterogeneity and control measures on the likelihood of outbreak extinction were also investigated.

scholarly journals A Mathematical Model For Lassa Fever Transmission Dynamics With Impacts of Control Measures: Analysis And Simulation

2021 ◽  
Vol 2 (2) ◽  
pp. 19-28
Author(s):  
Oke Isaiah Idisi ◽  
Tunde Tajudeen Yusuf
Keyword(s):  
Disease Transmission ◽  
Control Strategies ◽  
Disease Outbreaks ◽  
Lassa Fever ◽  
Control Measures ◽  
Transmission Dynamics ◽  
Effective Control ◽  
Lassa Virus ◽  
Long Run ◽  
Globally Stable

Lassa Fever, caused by Lassa virus, is a vector-host transmitted infectious disease whose prevalence has been on the upsurge over the past few decades. Thus, considering the grave implications of the continuous spread of the disease, an epidemic model was developed to describe the disease transmission dynamics with impacts of proposed control measures. This is to help inform effective control strategies that would successfully curtail and contain the disease in its endemic areas. The model is qualitatively analyzed in order to contextualize the long run behavior of the model while the model associated basic reproduction number $(\mathcal{R}_0)$ is derived. The model analysis reveals that the disease-free equilibrium is locally and globally stable whenever $ \mathcal{R}_0 < 1 $ and the disease prevalence would be high as long as $ \mathcal{R}_0 > 1 $. Finally, the model is numerically solved and simulated for different scenarios of the disease outbreaks while the findings from simulations are discussed.

scholarly journals Mathematical Modeling of Yellow Fever Transmission Dynamics with Multiple Control Measures

2019 ◽  
pp. 1-15 ◽  
Author(s):  
Tunde T. Yusuf ◽  
David O. Daniel
Keyword(s):  
Yellow Fever ◽  
Disease Transmission ◽  
Control Measures ◽  
Transmission Dynamics ◽  
Equilibrium Solutions ◽  
Multiple Control ◽  
Mosquito Net ◽  
Vector Population ◽  
The World ◽  
Existence And Stability

Yellow-fever disease remains endemic in some parts of the world despite the availability of a potent vaccine and effective treatment for the disease. This necessitates continuous research to possibly eradicate the spread of the disease and its attendant burden. Consequently, a deterministicmodel for Yellow-fever disease transmission dynamics within the human and vector population is considered. The model equilibrium solutions are obtained while the criteria for their existence and stability are investigated. The model is solved numerically using the forth order Runge- Kunta scheme and the results are simulated for different scenarios of interest. Findings from the simulations show that the disease will continue to be prevalent in our society (no matter how small) as long as the immunity conferred by the available vaccine is not lifelong and the Yellowfever infected mosquitoes continue to have unhindered access to humans. Thus, justifying the wisdom behind the practice of continuous vaccination and the use of mosquito net in areas of high Yellow-fever endemicity. However, it was equally found that the magnitude of the Yellowfever outbreak can be remarkably reduced to a negligible level with the adoption of chemical or biological control measures which ensure that only mosquitoes with minimal biting tendency thrive in the environment.

scholarly journals An Ebola virus disease model with fear and environmental transmission dynamics

2021 ◽  
Author(s):  
M.L. Juga ◽  
F. Nyabadza ◽  
F. Chirove
Keyword(s):  
Disease Transmission ◽  
Ebola Virus ◽  
Virus Disease ◽  
Case Fatality ◽  
Control Measures ◽  
Transmission Dynamics ◽  
Ebola Virus Disease ◽  
Fear Of Death ◽  
List Type ◽  
Environmental Transmission

ABSTRACTRecent Ebola virus disease (EVD) outbreaks have been limited not only to the interactions between humans but also to the complex interplay of the environment, human and socio-economic factors. Changes in human behaviour as a result of fear can also affect disease transmission dynamics. In this paper, a compartmental model is used to study the dynamics of EVD incorporating fear and environmental transmission. We formulate a fear dependent contact rate function to measure the rate of person to person, as well as pathogen to person transmissions. The epidemic threshold and the model equilibria are determined and, their stabilities are analysed. The model is validated by fitting it to data from the 2019 and 2020 EVD outbreaks in the Democratic Republic of Congo. Our results suggest that the fear of death from EVD may reduce the transmission and aid the control of the disease, but it is not sufficient to eradicate the disease. Policymakers need to also implement other control measures such as case finding, media campaigns, Quarantine and increase in the number of beds in the Ebola treatment centers, good laboratory services, safe burials and social mobilisation, to eradicate the disease.HighlightsDue to its high case fatality rate, EVD undoubtedly instills fear in the inhabitants of any affected community.We propose an Ebola model with fear, which considers the pathogens in the environment to quantify the effect of fear and environmental transmission on the EVD disease dynamics.The fear of death from Ebola is proportional to the Ebola disease transmission rate.At high levels of fear, the number of EVD cases decrease.

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