Determination of critical community size from an HIV/AIDS model

After an epidemic outbreak, the infection persists in a community long enough to engulf the entire susceptible population. Local extinction of the disease could be possible if the susceptible population gets depleted. In large communities, the tendency of eventual damp down of recurrent epidemics is balanced by random variability. But, in small communities, the infection would die out when the number of susceptible falls below a certain threshold. Critical community size (CCS) is considered to be the mentioned threshold, at which the infection is as likely as not to die out after a major epidemic for small communities unless reintroduced from outside. The determination of CCS could aid in devising systematic control strategies to eradicate the infectious disease from small communities. In this article, we have come up with a simplified computation based approach to deduce the CCS of HIV disease dynamics. We consider a deterministic HIV model proposed by Silva and Torres, and following Nåsell, introduce stochasticity in the model through time-varying population sizes of different compartments. Besides, Metcalf’s group observed that the relative risk of extinction of some infections on islands is almost double that in the mainlands i.e. infections cease to exist at a significantly higher rate in islands compared to the mainlands. They attributed this phenomenon to the greater recolonization in the mainlands. Interestingly, the application of our method on demographic facts and figures of countries in the AIDS belt of Africa led us to expect that existing control measures and isolated locations would assist in temporary eradication of HIV infection much faster. For example, our method suggests that through systematic control strategies, after 7.36 years HIV epidemics will temporarily be eradicated from different communes of island nation Madagascar, where the population size falls below its CCS value, unless the disease is reintroduced from outside.

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STOCHASTIC TRANSMISSION DYNAMICS OF COVID-19 WITHIN A DENSITY DEPENDENT POPULATION

FUDMA Journal of Sciences ◽

10.33003/659 ◽

2021 ◽

Vol 5 (2) ◽

pp. 567-573

Author(s):

Lubem M. Kwaghkor ◽

Stephen E. Onah ◽

Ibrahim G. Basi ◽

Theophilus Danjuma

Keyword(s):

Distribution Function ◽

Exponential Distribution ◽

Severe Disease ◽

The Elderly ◽

Control Measures ◽

Special Treatment ◽

Susceptible Population ◽

Density Dependent ◽

Infected People ◽

Population Sizes

Coronavirus diseases (COVID-19) is a respiratory disease. Most infected people are known to develop mild to moderate symptoms and recover without requiring special treatment except for those who have underlying medical conditions and the elderly have a higher risk of developing severe disease. This research is aimed at studying the probable spread of the COVID-19 virus within a completely susceptible density-dependent population using a modified exponential distribution function. The modified exponential distribution function was extended to include the Basic Reproduction Number which was computed using the Nigerian COVID-19 index cases from 27th February to 18th April, 2020 to be. Various interesting results were obtained for the including the time period for the spread for different population sizes. The duration of the spread of the virus is from 4 to 7 hours with an average of 5.5 hours. This indicates that, for one infectious person with to enter a completely susceptible population of size , the virus can spread through the entire population in about hours if no control measures are in place.

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Determination of Optimal Multiyear Air Pollution Control Policies

Journal of Dynamic Systems Measurement and Control ◽

10.1115/1.3426598 ◽

1972 ◽

Vol 94 (3) ◽

pp. 266-274 ◽

Cited By ~ 3

Author(s):

C. P. Kyan ◽

J. H. Seinfeld

Keyword(s):

Air Pollution ◽

Los Angeles ◽

Pollution Control ◽

Control Strategies ◽

Control Measures ◽

Air Pollution Control ◽

Pollutant Concentrations ◽

Control Procedures ◽

Discrete Dynamic Programming

A general theoretical framework for the determination of multiyear air pollution control strategies for an airshed is presented. It is assumed that emission control procedures are changed on a year-to-year basis. The problem considered is to determine the set of control measures that minimizes the total cost of control while maintaining specified levels of air quality each year. It is assumed that an airshed model exists which is capable of predicting pollutant concentrations as a function of source emissions in the airshed. It is shown that the general multiyear problem can be solved by discrete dynamic programming. The method is illustrated on the problem of determining control strategies for carbon monoxide for a three-year period in the Los Angeles basin.

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Phylogenetic Complexity of Morphologically Identified Anopheles squamosus in Southern Zambia

Insects ◽

10.3390/insects12020146 ◽

2021 ◽

Vol 12 (2) ◽

pp. 146

Author(s):

Jordan Hoffman ◽

Ilinca Ciubotariu ◽

Limonty Simubali ◽

Twig Mudenda ◽

William Moss ◽

...

Keyword(s):

Phylogenetic Relationships ◽

Catchment Area ◽

Control Strategies ◽

Light Trap ◽

Current Control ◽

Control Measures ◽

Morphological Identification ◽

The Past ◽

Blood Meal Source ◽

Residual Malaria Transmission

Despite dramatic reductions in malaria cases in the catchment area of Macha Hospital, Choma District, Southern Province in Zambia, prevalence has remained near 1–2% by RDT for the past several years. To investigate residual malaria transmission in the area, this study focuses on the relative abundance, foraging behavior, and phylogenetic relationships of Anopheles squamosus specimens. In 2011, higher than expected rates of anthropophily were observed among “zoophilic” An. squamosus, a species that had sporadically been found to contain Plasmodium falciparum sporozoites. The importance of An. squamosus in the region was reaffirmed in 2016 when P. falciparum sporozoites were detected in numerous An. squamosus specimens. This study analyzed Centers for Disease Control (CDC) light trap collections of adult mosquitoes from two collection schemes: one performed as part of a reactive-test-and-treat program and the second performed along a geographical transect. Morphological identification, molecular verification of anopheline species, and blood meal source were determined on individual samples. Data from these collections supported earlier studies demonstrating An. squamosus to be primarily exophagic and zoophilic, allowing them to evade current control measures. The phylogenetic relationships generated from the specimens in this study illustrate the existence of well supported clade structure among An. squamosus specimens, which further emphasizes the importance of molecular identification of vectors. The primarily exophagic behavior of An. squamosus in these collections also highlights that indoor vector control strategies will not be sufficient for elimination of malaria in southern Zambia.

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The Interplay between Campylobacter and the Caecal Microbial Community of Commercial Broiler Chickens over Time

Microorganisms ◽

10.3390/microorganisms9020221 ◽

2021 ◽

Vol 9 (2) ◽

pp. 221

Author(s):

Ilaria Patuzzi ◽

Massimiliano Orsini ◽

Veronica Cibin ◽

Sara Petrin ◽

Eleonora Mastrorilli ◽

...

Keyword(s):

Campylobacter Jejuni ◽

Broiler Chickens ◽

Control Strategies ◽

Chicken Meat ◽

Control Measures ◽

Microbial Network ◽

Gut Colonization ◽

Commercial Broiler ◽

Zoonotic Bacteria ◽

Human Infections

Campylobacter is the most frequent foodborne zoonotic bacteria worldwide, with chicken meat being overwhelmingly the most important reservoir for human infections. Control measures implemented at the farm level (i.e., biosecurity or vaccination), which have been successfully applied to limit other pathogens, such as Salmonella, have not been effective in reducing Campylobacter occurrence. Thus, new approaches are needed to fully understand the ecological interactions of Campylobacter with host animals to effectively comprehend its epidemiology. The objective of this study was to analyse longitudinally the gut microbiota composition of Campylobacter-infected and non-infected farms to identify any difference that could potentially be indicative of gut colonization by Campylobacter spp. Differences in the colonization rate and timing were observed at the farms that became positive for Campylobacter jejuni over the investigated time points, even though in positive tests, the occurrence of Campylobacter jejuni gut colonization was not observed before the second week of the life of the birds. Significant differences were observed in the abundances of specific bacterial taxa between the microbiota of individuals belonging to farms that became Campylobacter positive during the study and those who remained negative with particular reference to Bacteroidales and Clostridiales, respectively. Moreover, Campylobacter colonization dramatically influenced the microbiota richness, although to a different extent depending on the infection timing. Finally, a key role of Faecalibacterium and Lactobacillus genera on the Campylobacter microbial network was observed. Understanding the ecology of the Campylobacter interaction with host microbiota during infection could support novel approaches for broiler microbial barrier restoration. Therefore, evidence obtained through this study can be used to identify options to reduce the incidence of infection at a primary production level based on the targeted influence of the intestinal microbiota, thus helping develop new control strategies in order to mitigate the risk of human exposure to Campylobacter by chicken meat consumption.

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Effectiveness of SOx, NOx, and Primary Particulate Matter Control Strategies in the Improvement of Ambient PM Concentration in Taiwan

Atmosphere ◽

10.3390/atmos12040460 ◽

2021 ◽

Vol 12 (4) ◽

pp. 460

Author(s):

Jiun-Horng Tsai ◽

Ming-Ye Lee ◽

Hung-Lung Chiang

Keyword(s):

Particulate Matter ◽

Air Quality ◽

Model Simulation ◽

Control Strategies ◽

Ambient Air ◽

Clean Air Act ◽

Control Measures ◽

Control Plan ◽

Clean Air ◽

Pm2.5 Concentration

The Community Multiscale Air Quality (CMAQ) measurement was employed for evaluating the effectiveness of fine particulate matter control strategies in Taiwan. There are three scenarios as follows: (I) the 2014 baseline year emission, (II) 2020 emissions reduced via the Clean Air Act (CAA), and (III) other emissions reduced stringently via the Clean Air Act. Based on the Taiwan Emission Data System (TEDs) 8.1, established in 2014, the emission of particulate matter 2.5 (PM2.5) was 73.5 thousand tons y−1, that of SOx was 121.3 thousand tons y−1, and that of NOx was 404.4 thousand tons y−1 in Taiwan. The CMAQ model simulation indicated that the PM2.5 concentration was 21.9 μg m−3. This could be underestimated by 24% in comparison with data from the ambient air quality monitoring stations of the Taiwan Environmental Protection Administration (TEPA). The results of the simulation of the PM2.5 concentration showed high PM2.5 concentrations in central and southwestern Taiwan, especially in Taichung and Kaohsiung. Compared to scenario I, the average annual concentrations of PM2.5 for scenario II and scenario III showed reductions of 20.1% and 28.8%, respectively. From the results derived from the simulation, it can be seen that control of NOx emissions may improve daily airborne PM2.5 concentrations in Taiwan significantly and control of directly emitted PM2.5 emissions may improve airborne PM2.5 concentrations each month. Nevertheless, the results reveal that the preliminary control plan could not achievethe air quality standard. Therefore, the efficacy and effectiveness of the control measures must be considered to better reduce emissions in the future.

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Easing or tightening control strategies: determination of COVID-19 parameters for an agent-based model

Transportation ◽

10.1007/s11116-021-10210-7 ◽

2021 ◽

Author(s):

Ali Najmi ◽

Sahar Nazari ◽

Farshid Safarighouzhdi ◽

Eric J. Miller ◽

Raina MacIntyre ◽

...

Keyword(s):

Control Strategies ◽

Agent Based Model ◽

Agent Based

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Controlling the Spatial Spread of a Xylella Epidemic

Bulletin of Mathematical Biology ◽

10.1007/s11538-021-00861-z ◽

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.

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High insecticide resistance mediated by different mechanisms in Culex quinquefasciatus populations from the city of Yaoundé, Cameroon

Scientific Reports ◽

10.1038/s41598-021-86850-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Abdou Talipouo ◽

Konstantinos Mavridis ◽

Elysée Nchoutpouen ◽

Borel Djiappi-Tchamen ◽

Emmanouil Alexandros Fotakis ◽

...

Keyword(s):

Insecticide Resistance ◽

Vector Control ◽

High Resistance ◽

Culex Quinquefasciatus ◽

Control Strategies ◽

Cuticular Hydrocarbon ◽

Control Measures ◽

High Frequencies ◽

The City ◽

Integrated Vector Control

AbstractCulex mosquitoes particularly Culex quinquefasciatus are important arboviral and filariasis vectors, however despite this important epidemiological role, there is still a paucity of data on their bionomics. The present study was undertaken to assess the insecticide resistance status of Cx. quinquefasciatus populations from four districts of Yaoundé (Cameroon). All Culex quinquefasciatus populations except one displayed high resistance to bendiocarb and malathion with mortalities ranging from 0 to 89% while high resistance intensity against both permethrin and deltamethrin was recorded. Molecular analyses revealed high frequencies of the ACE-1 G119S mutation (ranging from 0 to 33%) and kdr L1014F allele (ranging from 55 to 74%) in all Cx. quinquefasciatus populations. Significant overexpression was detected for cytochrome P450s genes CYP6AA7 and CYP6Z10, as well as for Esterase A and Esterase B genes. The total cuticular hydrocarbon content, a proxy of cuticular resistance, was significantly increased (compared to the S-lab strain) in one population. The study confirms strong insecticide resistance mediated by different mechanisms in Cx. quinquefasciatus populations from the city of Yaoundé. The expansion of insecticide resistance in Culex populations could affect the effectiveness of current vector control measures and stress the need for the implementation of integrated vector control strategies in urban settings.

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From towers to walls: Trump’s border wall as entrepreneurial performance

Environment and Planning C Politics and Space ◽

10.1177/23996544211003097 ◽

2021 ◽

pp. 239965442110030

Author(s):

Åshild Kolås ◽

Lacin ldil Oztig

Keyword(s):

Control Strategies ◽

Family Separation ◽

Deferred Action ◽

Strong Focus ◽

Mexico Border ◽

Physical Attributes ◽

Southern Border ◽

Personal Skills ◽

Presidential Election Campaign

The pledge to build a “great”, “beautiful” southern border wall was a cornerstone of Donald J. Trump’s 2016 presidential election campaign. This paper analyzes Trump’s border wall project as an example of performative statecraft, suggesting that the wall works better rhetorically, than as a barrier against unauthorized cross-border movement. Identifying Trump’s performative statecraft as “entrepreneurial”, we argue that his border wall discourse differs from that of earlier presidents in the way Trump meshes the performance of the border wall as a protective device with his own performance as an entrepreneur and developer. Trump’s border wall discourse accentuates his personal skills as an entrepreneur, and makes these skills relevant to his key campaign promises: to “Make America Great Again”, and defend the nation against transnational crime. Despite Trump’s radical reformulation of US asylum policy, enhanced pursuit of unauthorized immigrants, termination of Obama-era programs like Deferred Action for Childhood Arrivals (DACA), and disturbing but short-lived family separation and ‘Zero-Tolerance’ detention scheme, the border security policies of President Trump are not as novel as his promotional campaigns would have us believe. In fact, Trump’s border control strategies have continued many of the measures introduced by earlier presidents. The novelty of the Trump presidency lies in the strong focus on the new US–Mexico border wall, and fervent attention to the physical attributes and instrumental functions of the wall. Much more than a fence, Trump’s proposed border wall is a grand, awe-inspiring monument to national security, and to Trump’s entrepreneurial statecraft. It also works as a visual aide for Trump’s plan to “Make America Great Again”. Border walls stand as testimony to the power of the state, and the determination of those who defend it. Trump’s border wall would be no exception.

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Molecular characterization of plasmid-mediated quinolone resistance (PMQR) and ESBLs-producing Klebsiella pneumonia isolated from an Iranian teaching hospital

10.21203/rs.3.rs-197852/v1 ◽

2021 ◽

Author(s):

Hamid Talebzadeh ◽

Hamid Mellali ◽

hamid solgi

Keyword(s):

Teaching Hospital ◽

Strong Association ◽

Control Measures ◽

Klebsiella Pneumonia ◽

The Public ◽

Isfahan Province ◽

Clonal Distribution ◽

Cross Transmission

Abstract Background The spread of plasmid-mediated multidrug resistance in Klebsiella pneumonia is a serious threat to the public health. We investigated the clinical characteristics and molecular epidemiology of K. pneumoniae isolated at a teaching hospital in Iran. Methods A total of 50 third-generation cephalosporins resistant K. pneumoniae strains were collected from patients’ clinical cultures. Antibiotic susceptibility testing and determination of MIC values for ceftazidime, cefotaxime and ciprofloxacin were performed. PCR and DNA sequencing were used to assess the presence of ESBL genes (blaCTX−M, blaTEM, blaSHV) and PMQR genes (qnrA, qnrB, qnrS, qepA, oqxA, oqxB and aac(6)-Ib-cr). Multilocus sequence typing (MLST) was performed on the strains to assess homology. Results Our results showed that the rates of resistance to all of antibiotics is high. All 50 K. pneumoniae strains harboured at least one of the ESBL resistance determinants. The blaCTX−M−15 gene was the major ESBLs determinant found in K. pneumoniae (88%; 44/50). PMQR was detected in 96% of the isolates and aac(6′)-Ib-cr was the most common (78% 39/50) followed by oqxA 36 (72%), oqxB 34 (68%), qnrS 20 (40%), qnrB 14 (28%) and qepA 1 (2%). MLST identified seven sequence types (STs), with the most common being ST11 (19/39). There was a strong association between PMQR genes (especially aac(6′)-Ib-cr) and ESBL genes. Conclusion The widespread detection of ESBLs-producing K. pneumoniae that co-carried PMQR determinants has become a threat to the treatment of infections in Isfahan Province of center Iran. Our findings suggest that K. pneumoniae ST11 and ST893 has a clonal distribution in our hospital. Therefore, this study highlighted the crucial need for implementing strict control measures to prevent cross transmission of these endemic clones.

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