Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 14.379
Filtrar
1.
Environ Monit Assess ; 192(11): 719, 2020 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-33083907

RESUMO

An environmental problem which is of concern across the globe nowadays is air pollution. The extent of air pollution is often studied based on data on the observed level of air pollution. Although the analysis of air pollution data that is available in the literature is numerous, studies on the dynamics of air pollution with the allowance for spatial interaction effects through the use of the Markov chain model are very limited. Accordingly, this study aims to explore the potential impact of spatial dependence over time and space on the distribution of air pollution based on the spatial Markov chain (SMC) model using the longitudinal air pollution index (API) data. This SMC model is pertinent to be applied since the daily data of API from 2012 to 2014 that have been gathered from 37 different air quality stations in Peninsular Malaysia is found to exhibit the property of spatial autocorrelation. Based on the spatial transition probability matrices found from the SMC model, specific characteristics of air pollution are studied in the regional context. These characteristics are the long-run proportion and the mean first passage time for each state of air pollution. It is found that the probability for a particular station's state to remain good is 0.814 if its neighbors are in a good state of air pollution and 0.7082 if its neighbors are in a moderate state. For a particular station having neighbors in a good state of air pollution, the proportion of time for it to continue being in a good state is 0.6. This proportion reduces to 0.4, 0.01, and 0 for the cell of moderate, unhealthy, and very unhealthy states, respectively. In addition, there exists a significant spatial dependence of API, indicating that air pollution for a particular station is dependent on the states of the neighboring stations.


Assuntos
Poluição do Ar , Monitoramento Ambiental , Poluição do Ar/análise , Malásia , Cadeias de Markov , Análise Espacial
2.
PLoS One ; 15(9): e0237627, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32877420

RESUMO

The ongoing COVID-19 epidemics poses a particular challenge to low and middle income countries, making some of them consider the strategy of "vertical confinement". In this strategy, contact is reduced only to specific groups (e.g. age groups) that are at increased risk of severe disease following SARS-CoV-2 infection. We aim to assess the feasibility of this scenario as an exit strategy for the current lockdown in terms of its ability to keep the number of cases under the health care system capacity. We developed a modified SEIR model, including confinement, asymptomatic transmission, quarantine and hospitalization. The population is subdivided into 9 age groups, resulting in a system of 72 coupled nonlinear differential equations. The rate of transmission is dynamic and derived from the observed delayed fatality rate; the parameters of the epidemics are derived with a Markov chain Monte Carlo algorithm. We used Brazil as an example of middle income country, but the results are easily generalizable to other countries considering a similar strategy. We find that starting from 60% horizontal confinement, an exit strategy on May 1st of confinement of individuals older than 60 years old and full release of the younger population results in 400 000 hospitalizations, 50 000 ICU cases, and 120 000 deaths in the 50-60 years old age group alone. Sensitivity analysis shows the 95% confidence interval brackets a order of magnitude in cases or three weeks in time. The health care system avoids collapse if the 50-60 years old are also confined, but our model assumes an idealized lockdown where the confined are perfectly insulated from contamination, so our numbers are a conservative lower bound. Our results discourage confinement by age as an exit strategy.


Assuntos
Infecções por Coronavirus/patologia , Modelos Teóricos , Pneumonia Viral/patologia , Fatores Etários , Betacoronavirus/isolamento & purificação , Brasil/epidemiologia , Infecções por Coronavirus/epidemiologia , Infecções por Coronavirus/transmissão , Infecções por Coronavirus/virologia , Humanos , Cadeias de Markov , Método de Monte Carlo , Pandemias , Pneumonia Viral/epidemiologia , Pneumonia Viral/transmissão , Pneumonia Viral/virologia , Quarentena
3.
Lancet Glob Health ; 8(10): e1282-e1294, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32971051

RESUMO

BACKGROUND: Worldwide, smoking tobacco causes 7 million deaths annually, and this toll is expected to increase, especially in low-income and middle-income countries. In Latin America, smoking is a leading risk factor for death and disability, contributes to poverty, and imposes an economic burden on health systems. Despite being one of the most effective measures to reduce smoking, tobacco taxation is underused and cigarettes are more affordable in Latin America than in other regions. Our aim was to estimate the tobacco-attributable burden on mortality, disease incidence, quality of life lost, and medical costs in 12 Latin American countries, and the expected health and economic effects of increasing tobacco taxes. METHODS: In this modelling study, we developed a Markov probabilistic microsimulation economic model of the natural history, medical costs, and quality-of-life losses associated with the most common tobacco-related diseases in 12 countries in Latin America. Data inputs were obtained through a literature review, vital statistics, and hospital databases from each country: Argentina, Bolivia, Brazil, Chile, Colombia, Costa Rica, Ecuador, Honduras, Mexico, Paraguay, Peru, and Uruguay. The main outcomes of the model are life-years, quality-adjusted life-years, disease events, hospitalisations, disease incidence, disease cost, and healthy years of life lost. We estimated direct medical costs for each tobacco-related disease included in the model using a common costing methodology for each country. The disease burden was estimated as the difference in disease events, deaths, and associated costs between the results predicted by the model for current smoking prevalence and a hypothetical cohort of people in each country who had never smoked. The model estimates the health and financial effects of a price increase of cigarettes through taxes, in terms of disease and health-care costs averted, and increased tax revenues. FINDINGS: In the 12 Latin American countries analysed, we estimated that smoking is responsible for approximately 345 000 (12%) of the total 2 860 921 adult deaths, 2·21 million disease events, 8·77 million healthy years of life lost, and $26·9 billion in direct medical costs annually. Health-care costs attributable to smoking were estimated to represent 6·9% of the health budgets of these countries, equivalent to 0·6% of their gross domestic product. Tax revenues from cigarette sales cover 36·0% of the estimated health expenditures caused by smoking. We estimated that a 50% increase in cigarette price through taxation would avert more than 300 000 deaths, 1·3 million disease events, gain 9 million healthy life-years, and save $26·7 billion in health-care costs in the next 10 years, with a total economic benefit of $43·7 billion. INTERPRETATION: Smoking represents a substantial health and economic burden in these 12 countries of Latin America. Tobacco tax increases could successfully avert deaths and disability, reduce health-care spending, and increase tax revenues, resulting in large net economic benefits. FUNDING: International Development Research Centre (IDRC), Canada.


Assuntos
Efeitos Psicossociais da Doença , Custos de Cuidados de Saúde/estatística & dados numéricos , Fumar/economia , Fumar/epidemiologia , Impostos/economia , Produtos do Tabaco/economia , Humanos , América Latina/epidemiologia , Cadeias de Markov , Modelos Econômicos , Impostos/estatística & dados numéricos , Produtos do Tabaco/estatística & dados numéricos
4.
Lancet Glob Health ; 8(10): e1335-e1344, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32971056

RESUMO

BACKGROUND: Coinciding with the release of the first Chinese domestic human papillomavirus (HPV) vaccine Cecolin in 2019, and the substantial advancements in cervical cancer screening technology, we aimed to evaluate the cost-effectiveness of the combined strategies of cervical cancer screening programmes and universal vaccination of girls (aged 9-14 years) with Cecolin in China. METHODS: We did a cost-effectiveness analysis in China, in which we developed a Markov model of cervical cancer to evaluate the incremental cost-effectiveness ratios of 61 intervention strategies, including a combination of various screening methods at different frequencies with and without vaccination, and also vaccination alone, from a health-care system perspective. We did univariate and probabilistic sensitivity analyses to assess the robustness of the model's findings. FINDINGS: Compared with no intervention, various combined screening and vaccination strategies would incur an additional cost of US$6 157 000-22 146 000 and result in 691-970 quality-adjusted life-years (QALYs) gained in a designated cohort of 100 000 girls aged 9-14 years over a lifetime. With a willingness-to-pay threshold of three times the Chinese per-capita gross domestic product (GDP), careHPV screening (a rapid HPV test) once every 5 years with vaccination would be the most cost-effective strategy with an incremental cost-effectiveness ratio of $21 799 per QALY compared with the lower-cost non-dominated strategy on the cost-effectiveness frontier, and the probability of it being cost-effective (44%) outperformed other strategies. Strategies that combined screening and vaccination would be more cost-effective than screening alone strategies when the vaccination cost was less than $50 for two doses, even with a lower willingness-to-pay of one times the per-capita GDP. INTERPRETATION: careHPV screening once every 5 years with vaccination is the most cost-effective strategy for cervical cancer prevention in China. A reduction in the domestic HPV vaccine price is necessary to ascertain a good economic return for the future vaccination programme. The findings provide important evidence that informs health policies for cervical cancer prevention in China. FUNDING: National Natural Science Foundation of China.


Assuntos
Análise Custo-Benefício/economia , Análise Custo-Benefício/estatística & dados numéricos , Infecções por Papillomavirus/prevenção & controle , Vacinas contra Papillomavirus/economia , Neoplasias do Colo do Útero/economia , Neoplasias do Colo do Útero/prevenção & controle , Adolescente , Criança , China , Estudos de Coortes , Análise Custo-Benefício/métodos , Feminino , Humanos , Cadeias de Markov , Infecções por Papillomavirus/economia
5.
J Korean Med Sci ; 35(35): e321, 2020 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-32893522

RESUMO

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic has posed significant global public health challenges and created a substantial economic burden. Korea has experienced an extensive outbreak, which was linked to a religion-related super-spreading event. However, the implementation of various non-pharmaceutical interventions (NPIs), including social distancing, spring semester postponing, and extensive testing and contact tracing controlled the epidemic. Herein, we estimated the effectiveness of each NPI using a simulation model. METHODS: A compartment model with a susceptible-exposed-infectious-quarantined-hospitalized structure was employed. Using the Monte-Carlo-Markov-Chain algorithm with Gibbs' sampling method, we estimated the time-varying effective contact rate to calibrate the model with the reported daily new confirmed cases from February 12th to March 31st (7 weeks). Moreover, we conducted scenario analyses by adjusting the parameters to estimate the effectiveness of NPI. RESULTS: Relaxed social distancing among adults would have increased the number of cases 27.4-fold until the end of March. Spring semester non-postponement would have increased the number of cases 1.7-fold among individuals aged 0-19, while lower quarantine and detection rates would have increased the number of cases 1.4-fold. CONCLUSION: Among the three NPI measures, social distancing in adults showed the highest effectiveness. The substantial effect of social distancing should be considered when preparing for the 2nd wave of COVID-19.


Assuntos
Controle de Doenças Transmissíveis/métodos , Busca de Comunicante/métodos , Infecções por Coronavirus/transmissão , Programas de Rastreamento/métodos , Pneumonia Viral/transmissão , Distância Social , Betacoronavirus , Simulação por Computador , Exposição Ambiental/prevenção & controle , Humanos , Cadeias de Markov , Modelos Teóricos , Método de Monte Carlo , Pandemias , Prática de Saúde Pública/legislação & jurisprudência , República da Coreia
6.
Math Biosci Eng ; 17(4): 2842-2852, 2020 03 25.
Artigo em Inglês | MEDLINE | ID: mdl-32987501

RESUMO

Since the first case of coronavirus disease (COVID-19) in Wuhan Hubei, China, was reported in December 2019, COVID-19 has spread rapidly across the country and overseas. The first case in Anhui, a province of China, was reported on January 10, 2020. In the field of infectious diseases, modeling, evaluating and predicting the rate of disease transmission is very important for epidemic prevention and control. Different intervention measures have been implemented starting from different time nodes in the country and Anhui, the epidemic may be divided into three stages for January 10 to February 11, 2020, namely. We adopted interrupted time series method and develop an SEI/QR model to analyse the data. Our results displayed that the lockdown of Wuhan implemented on January 23, 2020 reduced the contact rate of epidemic transmission in Anhui province by 48.37%, and centralized quarantine management policy for close contacts in Anhui reduced the contact rate by an additional 36.97%. At the same time, the estimated basic reproduction number gradually decreased from the initial 2.9764 to 0.8667 and then to 0.5725. We conclude that the Wuhan lockdown and the centralized quarantine management policy in Anhui played a crucial role in the timely and effective mitigation of the epidemic in Anhui. One merit of this work is the adoption of morbidity data which may reflect the epidemic more accurately and promptly. Our estimated parameters are largely in line with the World Health Organization estimates and previous studies.


Assuntos
Betacoronavirus , Infecções por Coronavirus/epidemiologia , Modelos Biológicos , Pandemias , Pneumonia Viral/epidemiologia , Número Básico de Reprodução/estatística & dados numéricos , China/epidemiologia , Simulação por Computador , Infecções por Coronavirus/prevenção & controle , Infecções por Coronavirus/transmissão , Humanos , Análise de Séries Temporais Interrompida/estatística & dados numéricos , Cadeias de Markov , Conceitos Matemáticos , Método de Monte Carlo , Morbidade/tendências , Pandemias/prevenção & controle , Pandemias/estatística & dados numéricos , Pneumonia Viral/prevenção & controle , Pneumonia Viral/transmissão , Quarentena/estatística & dados numéricos
7.
Math Biosci Eng ; 17(4): 3052-3061, 2020 04 08.
Artigo em Inglês | MEDLINE | ID: mdl-32987516

RESUMO

The novel coronavirus disease 2019 (COVID-19) infection broke out in December 2019 in Wuhan, and rapidly overspread 31 provinces in mainland China on 31 January 2020. In the face of the increasing number of daily confirmed infected cases, it has become a common concern and worthy of pondering when the infection will appear the turning points, what is the final size and when the infection would be ultimately controlled. Based on the current control measures, we proposed a dynamical transmission model with contact trace and quarantine and predicted the peak time and final size for daily confirmed infected cases by employing Markov Chain Monte Carlo algorithm. We estimate the basic reproductive number of COVID-19 is 5.78 (95%CI: 5.71-5.89). Under the current intervention before 31 January, the number of daily confirmed infected cases is expected to peak on around 11 February 2020 with the size of 4066 (95%CI: 3898-4472). The infection of COVID-19 might be controlled approximately after 18 May 2020. Reducing contact and increasing trace about the risk population are likely to be the present effective measures.


Assuntos
Betacoronavirus , Infecções por Coronavirus/epidemiologia , Modelos Biológicos , Pandemias/estatística & dados numéricos , Pneumonia Viral/epidemiologia , Algoritmos , Número Básico de Reprodução/estatística & dados numéricos , China/epidemiologia , Simulação por Computador , Busca de Comunicante/estatística & dados numéricos , Infecções por Coronavirus/prevenção & controle , Infecções por Coronavirus/transmissão , Epidemias/prevenção & controle , Epidemias/estatística & dados numéricos , Mapeamento Geográfico , Humanos , Cadeias de Markov , Conceitos Matemáticos , Método de Monte Carlo , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , Pneumonia Viral/transmissão , Quarentena/estatística & dados numéricos
8.
Math Biosci Eng ; 17(4): 3618-3636, 2020 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-32987547

RESUMO

A new COVID-19 epidemic model with media coverage and quarantine is constructed. The model allows for the susceptibles to the unconscious and conscious susceptible compartment. First, mathematical analyses establish that the global dynamics of the spread of the COVID-19 infectious disease are completely determined by the basic reproduction number R0. If R0 ≤ 1, then the disease free equilibrium is globally asymptotically stable. If R0 > 1, the endemic equilibrium is globally asymptotically stable. Second, the unknown parameters of model are estimated by the MCMC algorithm on the basis of the total confirmed new cases from February 1, 2020 to March 23, 2020 in the UK. We also estimate that the basic reproduction number is R0 = 4.2816(95%CI: (3.8882, 4.6750)). Without the most restrictive measures, we forecast that the COVID-19 epidemic will peak on June 2 (95%CI: (May 23, June 13)) (Figure 3a) and the number of infected individuals is more than 70% of UK population. In order to determine the key parameters of the model, sensitivity analysis are also explored. Finally, our results show reducing contact is effective against the spread of the disease. We suggest that the stringent containment strategies should be adopted in the UK.


Assuntos
Betacoronavirus , Meios de Comunicação , Infecções por Coronavirus/epidemiologia , Pandemias , Pneumonia Viral/epidemiologia , Quarentena , Algoritmos , Número Básico de Reprodução/estatística & dados numéricos , Infecções por Coronavirus/prevenção & controle , Infecções por Coronavirus/transmissão , Humanos , Cadeias de Markov , Conceitos Matemáticos , Modelos Biológicos , Método de Monte Carlo , Pandemias/prevenção & controle , Pandemias/estatística & dados numéricos , Pneumonia Viral/prevenção & controle , Pneumonia Viral/transmissão , Fatores de Tempo , Reino Unido/epidemiologia
9.
Math Biosci Eng ; 17(4): 3637-3648, 2020 05 18.
Artigo em Inglês | MEDLINE | ID: mdl-32987548

RESUMO

Based on the reported data from February 16, 2020 to March 9, 2020 in South Korea including confirmed cases, death cases and recovery cases, the control reproduction number was estimated respectively at different control measure phases using Markov chain Monte Carlo method and presented using the resulting posterior mean and 95% credible interval (CrI). At the early phase from February 16 to February 24, we estimate the basic reproduction number R0 of COVID-19 to be 4.79(95% CrI 4.38 - 5.2). The estimated control reproduction number dropped rapidly to Rc ≈ 0.32(95% CrI 0.19 - 0.47) at the second phase from February 25 to March 2 because of the voluntary lockdown measures. At the third phase from March 3 to March 9, we estimate Rc to be 0.27 (95% CrI 0.14 - 0.42). We predict that the final size of the COVID-19 outbreak in South Korea is 9661 (95% CrI 8660 - 11100) and the whole epidemic will be over by late April. It is found that reducing contact rate and enhancing the testing speed will have the impact on the peak value and the peak time.


Assuntos
Betacoronavirus , Infecções por Coronavirus/epidemiologia , Pandemias , Pneumonia Viral/epidemiologia , Número Básico de Reprodução/estatística & dados numéricos , Simulação por Computador , Infecções por Coronavirus/prevenção & controle , Infecções por Coronavirus/transmissão , Surtos de Doenças/prevenção & controle , Surtos de Doenças/estatística & dados numéricos , Humanos , Cadeias de Markov , Conceitos Matemáticos , Modelos Biológicos , Método de Monte Carlo , Pandemias/prevenção & controle , Pandemias/estatística & dados numéricos , Pneumonia Viral/prevenção & controle , Pneumonia Viral/transmissão , República da Coreia/epidemiologia , Fatores de Tempo
10.
Math Biosci Eng ; 17(4): 3710-3720, 2020 05 21.
Artigo em Inglês | MEDLINE | ID: mdl-32987551

RESUMO

Since December 2019, an outbreak of a novel coronavirus pneumonia (WHO named COVID-19) swept across China. In Shanxi Province, the cumulative confirmed cases finally reached 133 since the first confirmed case appeared on January 22, 2020, and most of which were imported cases from Hubei Province. Reasons for this ongoing surge in Shanxi province, both imported and autochthonous infected cases, are currently unclear and demand urgent investigation. In this paper, we developed a SEIQR difference-equation model of COVID-19 that took into account the transmission with discrete time imported cases, to perform assessment and risk analysis. Our findings suggest that if the lock-down date in Wuhan is earlier, the infectious cases are fewer. Moreover, we reveal the effects of city lock-down date on the final scale of cases: if the date is advanced two days, the cases may decrease one half (67, 95% CI: 66-68); if the date is delayed for two days, the cases may reach about 196 (95% CI: 193-199). Our investigation model could be potentially helpful to study the transmission of COVID-19, in other provinces of China except Hubei. Especially, the method may also be used in countries with the first confirmed case is imported.


Assuntos
Betacoronavirus , Infecções por Coronavirus/transmissão , Modelos Biológicos , Pandemias , Pneumonia Viral/transmissão , Número Básico de Reprodução/estatística & dados numéricos , China/epidemiologia , Simulação por Computador , Infecções por Coronavirus/epidemiologia , Infecções por Coronavirus/prevenção & controle , Humanos , Cadeias de Markov , Conceitos Matemáticos , Método de Monte Carlo , Pandemias/prevenção & controle , Pandemias/estatística & dados numéricos , Pneumonia Viral/epidemiologia , Pneumonia Viral/prevenção & controle , Quarentena/estatística & dados numéricos , Fatores de Tempo , Viagem/estatística & dados numéricos
11.
PLoS One ; 15(8): e0236226, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32866160

RESUMO

Amine oxidases (AOs) including copper containing amine oxidases (CuAOs) and FAD-dependent polyamine oxidases (PAOs) are associated with polyamine catabolism in the peroxisome, apoplast and cytoplasm and play an essential role in growth and developmental processes and response to biotic and abiotic stresses. Here, we identified PAO genes in common wheat (Triticum aestivum), T. urartu and Aegilops tauschii and reported the genome organization, evolutionary features and expression profiles of the wheat PAO genes (TaPAO). Expression analysis using publicly available RNASeq data showed that TaPAO genes are expressed redundantly in various tissues and developmental stages. A large percentage of TaPAOs respond significantly to abiotic stresses, especially temperature (i.e. heat and cold stress). Some TaPAOs were also involved in response to other stresses such as powdery mildew, stripe rust and Fusarium infection. Overall, TaPAOs may have various functions in stress tolerances responses, and play vital roles in different tissues and developmental stages. Our results provided a reference for further functional investigation of TaPAO proteins.


Assuntos
Resposta ao Choque Frio/genética , Oxirredutases atuantes sobre Doadores de Grupo CH-NH/genética , Proteínas de Plantas/genética , Termotolerância/genética , Triticum/genética , Aegilops/enzimologia , Aegilops/genética , Processamento Alternativo , Sequência de Aminoácidos , Conjuntos de Dados como Assunto , Evolução Molecular , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Genoma de Planta , Estudo de Associação Genômica Ampla , Cadeias de Markov , Modelos Genéticos , Peso Molecular , Família Multigênica , Oxirredutases atuantes sobre Doadores de Grupo CH-NH/química , Oxirredutases atuantes sobre Doadores de Grupo CH-NH/metabolismo , Filogenia , Proteínas de Plantas/química , Proteínas de Plantas/metabolismo , Domínios Proteicos/genética , RNA-Seq , Alinhamento de Sequência , Triticum/enzimologia
12.
PLoS One ; 15(9): e0237492, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32877432

RESUMO

Oncimmune's EarlyCDT®-Lung is a simple ELISA blood test that measures seven lung cancer specific autoantibodies and is used in the assessment of malignancy risk in patients with indeterminate pulmonary nodules (IPNs). The objective of this study was to examine the cost-effectiveness of EarlyCDT-Lung in the diagnosis of lung cancer amongst patients with IPNs in addition to CT surveillance, compared to CT surveillance alone which is the current recommendation by the British Thoracic Society guidelines. A model consisting of a combination of a decision tree and Markov model was developed using the outcome measure of the quality adjusted life year (QALY). A life-time time horizon was adopted. The model was parameterized using a range of secondary sources. At £70 per test, EarlyCDT-Lung and CT surveillance was found to be cost-effective compared to CT surveillance alone with an incremental cost-effectiveness ratio (ICER) of less than £2,500 depending on the test accuracy parameters used. It was also found that EarlyCDT-Lung can be priced up to £1,177 and still be cost-effective based on cost-effectiveness acceptance threshold of £20,000 / QALY. Further research to resolve parameter uncertainty, was not found to be of value. The results here demonstrate that at £70 per test the EarlyCDT-Lung will have a positive impact on patient outcomes and coupled with CT surveillance is a cost-effective approach to the management of patients with IPNs. The conclusions drawn from this analysis are robust to realistic variation in the parameters used in the model.


Assuntos
Autoanticorpos/imunologia , Análise Custo-Benefício , Neoplasias Pulmonares/diagnóstico , Neoplasias Pulmonares/economia , Nódulos Pulmonares Múltiplos/complicações , Tomografia Computadorizada por Raios X , Progressão da Doença , Humanos , Neoplasias Pulmonares/diagnóstico por imagem , Neoplasias Pulmonares/imunologia , Cadeias de Markov , Nódulos Pulmonares Múltiplos/diagnóstico por imagem , Probabilidade , Análise de Sobrevida
13.
PLoS One ; 15(8): e0237126, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32756608

RESUMO

The Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has highlighted the need for performing accurate inference with limited data. Fundamental to the design of rapid state responses is the ability to perform epidemiological model parameter inference for localised trajectory predictions. In this work, we perform Bayesian parameter inference using Markov Chain Monte Carlo (MCMC) methods on the Susceptible-Infected-Recovered (SIR) and Susceptible-Exposed-Infected-Recovered (SEIR) epidemiological models with time-varying spreading rates for South Africa. The results find two change points in the spreading rate of COVID-19 in South Africa as inferred from the confirmed cases. The first change point coincides with state enactment of a travel ban and the resultant containment of imported infections. The second change point coincides with the start of a state-led mass screening and testing programme which has highlighted community-level disease spread that was not well represented in the initial largely traveller based and private laboratory dominated testing data. The results further suggest that due to the likely effect of the national lockdown, community level transmissions are slower than the original imported case driven spread of the disease.


Assuntos
Teorema de Bayes , Infecções por Coronavirus/epidemiologia , Pneumonia Viral/epidemiologia , Algoritmos , Infecções por Coronavirus/diagnóstico , Infecções por Coronavirus/transmissão , Infecções por Coronavirus/virologia , Humanos , Cadeias de Markov , Método de Monte Carlo , Pandemias , Pneumonia Viral/diagnóstico , Pneumonia Viral/transmissão , Pneumonia Viral/virologia , África do Sul/epidemiologia
14.
PLoS One ; 15(8): e0236776, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32760158

RESUMO

We analyzed COVID-19 data through May 6th, 2020 using a partially observed Markov process. Our method uses a hybrid deterministic and stochastic formalism that allows for time variable transmission rates and detection probabilities. The model was fit using iterated particle filtering to case count and death count time series from 55 countries. We found evidence for a shrinking epidemic in 30 of the 55 examined countries. Of those 30 countries, 27 have significant evidence for subcritical transmission rates, although the decline in new cases is relatively slow compared to the initial growth rates. Generally, the transmission rates in Europe were lower than in the Americas and Asia. This suggests that global scale social distancing efforts to slow the spread of COVID-19 are effective although they need to be strengthened in many regions and maintained in others to avoid further resurgence of COVID-19. The slow decline also suggests alternative strategies to control the virus are needed before social distancing efforts are partially relaxed.


Assuntos
Infecções por Coronavirus/epidemiologia , Pneumonia Viral/epidemiologia , América/epidemiologia , Ásia/epidemiologia , Betacoronavirus/isolamento & purificação , Infecções por Coronavirus/diagnóstico , Infecções por Coronavirus/transmissão , Infecções por Coronavirus/virologia , Bases de Dados Factuais , Europa (Continente)/epidemiologia , Humanos , Cadeias de Markov , Pandemias , Pneumonia Viral/diagnóstico , Pneumonia Viral/transmissão , Pneumonia Viral/virologia
15.
Phys Rev Lett ; 125(4): 048105, 2020 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-32794803

RESUMO

Environmental changes greatly influence the evolution of populations. Here, we study the dynamics of a population of two strains, one growing slightly faster than the other, competing for resources in a time-varying binary environment modeled by a carrying capacity switching either randomly or periodically between states of abundance and scarcity. The population dynamics is characterized by demographic noise (birth and death events) coupled to a varying environment. We elucidate the similarities and differences of the evolution subject to a stochastically and periodically varying environment. Importantly, the population size distribution is generally found to be broader under intermediate and fast random switching than under periodic variations, which results in markedly different asymptotic behaviors between the fixation probability of random and periodic switching. We also determine the detailed conditions under which the fixation probability of the slow strain is maximal.


Assuntos
Meio Ambiente , Modelos Biológicos , Dinâmica Populacional , Evolução Biológica , Cadeias de Markov , Processos Estocásticos
16.
Public Health Rep ; 135(1_suppl): 172S-181S, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32735191

RESUMO

OBJECTIVE: Targeted testing and treatment of persons with latent tuberculosis infection (LTBI) is a critical component of the US tuberculosis (TB) elimination strategy. In January 2016, the California Department of Public Health issued a tool and user guide for TB risk assessment (California tool) and guidance for LTBI testing, and in September 2016, the US Preventive Services Task Force (USPSTF) issued recommendations for LTBI testing in primary care settings. We estimated the epidemiologic effect of adherence to both recommendations in California. METHODS: We used an individual-based Markov micro-simulation model to estimate the number of cases of TB disease expected through 2026 with baseline LTBI strategies compared with implementation of the USPSTF or California tool guidance. We estimated the risk of LTBI by age and country of origin, the probability of being in a targeted population, and the probability of presenting for primary care based on available data. We assumed 100% adherence to testing guidance but imperfect adherence to treatment. RESULTS: Implementation of USPSTF and California tool guidance would result in nearly identical numbers of tests administered and cases of TB disease prevented. Perfect adherence to either recommendation would result in approximately 7000 cases of TB disease averted (40% reduction compared with baseline) by 2026. Almost all of this decline would be driven by a reduction in the number of cases among non-US-born persons. CONCLUSIONS: By focusing on the non-US-born population, adherence to LTBI testing strategies recommended by the USPSTF and the California tool could substantially reduce the burden of TB disease in California in the next decade.


Assuntos
Tuberculose Latente/diagnóstico , Atenção Primária à Saúde/organização & administração , Adulto , Fatores Etários , Antituberculosos/uso terapêutico , California , Emigrantes e Imigrantes , Fidelidade a Diretrizes , Humanos , Hospedeiro Imunocomprometido , Tuberculose Latente/tratamento farmacológico , Tuberculose Latente/etnologia , Cadeias de Markov , Programas de Rastreamento , Guias de Prática Clínica como Assunto , Atenção Primária à Saúde/normas , Instituições Residenciais , Medição de Risco , Tuberculose/etnologia
17.
BMC Med Res Methodol ; 20(1): 209, 2020 08 12.
Artigo em Inglês | MEDLINE | ID: mdl-32787822

RESUMO

BACKGROUND: As the whole world is experiencing the cascading effect of a new pandemic, almost every aspect of modern life has been disrupted. Because of health emergencies during this period, widespread fear has resulted in compromised patient safety, especially for patients with cancer. It is very challenging to treat such cancer patients because of the complexity of providing care and treatment, along with COVID-19. Hence, an effective treatment comparison strategy is needed. We need to have a handy tool to understand cancer progression in this unprecedented scenario. Linking different events of cancer progression is the need of the hour. It is a huge challenge for the development of new methodology. METHODS: This article explores the time lag effect and makes a statistical inference about the best experimental arm using Accelerated Failure Time (AFT) model and regression methods. The work is presented as the occurrence of other events as a hazard rate after the first event (relapse). The time lag effect between the events is linked and analysed. RESULTS: The results were presented as a comprehensive analytical strategy by joining all disease progression. An AFT model applied with the transition states, and the dependency structure between the gap times was used by the auto-regression model. The effects of arms were compared using the coefficient of auto-regression and accelerated failure time (AFT) models. CONCLUSIONS: We provide the solutions to overcome the issue with intervals between two consecutive events in motivating head and neck cancer (HNC) data. COVID-19 is not going to leave us soon. We have to conduct several cancer clinical trials in the presence of COVID-19. A comprehensive analytical strategy to analyse cancer clinical trial data during COVID-19 pandemic is presented.


Assuntos
Algoritmos , Infecções por Coronavirus/prevenção & controle , Neoplasias de Cabeça e Pescoço/terapia , Oncologia/métodos , Modelos Teóricos , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , Teorema de Bayes , Betacoronavirus/fisiologia , Infecções por Coronavirus/complicações , Infecções por Coronavirus/virologia , Progressão da Doença , Neoplasias de Cabeça e Pescoço/complicações , Neoplasias de Cabeça e Pescoço/diagnóstico , Humanos , Estimativa de Kaplan-Meier , Cadeias de Markov , Método de Monte Carlo , Recidiva Local de Neoplasia , Pneumonia Viral/complicações , Pneumonia Viral/virologia
18.
PLoS One ; 15(8): e0237172, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32817623

RESUMO

This paper contributes to better understand the dynamic interactions between effective exchange rate (EER) and oil price for an oil-importing country like the U.S. by considering a Time-Varying Parameter VAR model with the use of monthly data from 1974:01 to 2019:07. Our findings show a depreciation after an oil price shock in the short-run for any period of time, although the pattern of long-run responses of U.S. EER is diverse across time periods, with an appreciation being observed before the mid-2000s and after the mid-2010s, and a depreciation between both periods. This diversity of response should lead policy makers to react differently in order to counteract such shocks. Furthermore, the reaction of oil price to an appreciation of U.S. EER is negative and different over time, which may generate different adverse effects on investment. The knowledge of such effects may help financial investors to diversify their investments in order to optimize the risk-return profile of their portfolios.


Assuntos
Comércio , Modelos Econômicos , Petróleo/economia , Teorema de Bayes , Humanos , Investimentos em Saúde/economia , Cadeias de Markov , Distribuição Normal , Estados Unidos
19.
PLoS One ; 15(8): e0236089, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32790775

RESUMO

Multiscale geometric analysis (MGA) is not only characterized by multi-resolution, time-frequency localization, multidirectionality and anisotropy, but also outdoes the limitations of wavelet transform in representing high-dimensional singular data such as edges and contours. Therefore, researchers have been exploring new MGA-based image compression standards rather than the JPEG2000 standard. However, due to the difference in terms of the data structure, redundancy and decorrelation between wavelet and MGA, as well as the complexity of the coding scheme, so far, no definitive researches have been reported on the MGA-based image coding schemes. In addressing this problem, this paper proposes an image data compression approach using the hidden Markov model (HMM)/pulse-coupled neural network (PCNN) model in the contourlet domain. First, a sparse decomposition of an image was performed using a contourlet transform to obtain the coefficients that show the multiscale and multidirectional characteristics. An HMM was then adopted to establish links between coefficients in neighboring subbands of different levels and directions. An Expectation-Maximization (EM) algorithm was also adopted in training the HMM in order to estimate the state probability matrix, which maintains the same structure of the contourlet decomposition coefficients. In addition, each state probability can be classified by the PCNN based on the state probability distribution. Experimental results show that the HMM/PCNN -contourlet model proposed in this paper leads to better compression performance and offer a more flexible encoding scheme.


Assuntos
Compressão de Dados/métodos , Redes Neurais de Computação , Análise de Ondaletas , Cadeias de Markov
20.
Nat Commun ; 11(1): 3872, 2020 08 03.
Artigo em Inglês | MEDLINE | ID: mdl-32747627

RESUMO

The optimal post-treatment surveillance strategy that can detect early recurrence of a cancer within limited visits remains unexplored. Here we adopt nasopharyngeal carcinoma as the study model to establish an approach to surveillance that balances the effectiveness of disease detection versus costs. A total of 7,043 newly-diagnosed patients are grouped according to a clinic-molecular risk grouping system. We use a random survival forest model to simulate the monthly probability of disease recurrence, and thereby establish risk-based surveillance arrangements that can maximize the efficacy of recurrence detection per visit. Markov decision-analytic models further validate that the risk-based surveillance outperforms the control strategies and is the most cost-effective. These results are confirmed in an external validation cohort. Finally, we recommend the risk-based surveillance arrangement which requires 10, 11, 13 and 14 visits for group I to IV. Our surveillance strategies might pave the way for individualized and economic surveillance for cancer survivors.


Assuntos
Sobreviventes de Câncer , Monitorização Fisiológica/métodos , Carcinoma Nasofaríngeo/terapia , Neoplasias Nasofaríngeas/terapia , Adulto , Análise Custo-Benefício , Intervalo Livre de Doença , Feminino , Humanos , Masculino , Cadeias de Markov , Pessoa de Meia-Idade , Monitorização Fisiológica/economia , Carcinoma Nasofaríngeo/diagnóstico , Carcinoma Nasofaríngeo/economia , Neoplasias Nasofaríngeas/diagnóstico , Neoplasias Nasofaríngeas/economia , Recidiva Local de Neoplasia , Medicina de Precisão/economia , Medicina de Precisão/métodos , Fatores de Risco
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA