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https://www.readbyqxmd.com/read/28812540/quantifying-transmission
#1
Mark Woolhouse
Transmissibility is the defining characteristic of infectious diseases. Quantifying transmission matters for understanding infectious disease epidemiology and designing evidence-based disease control programs. Tracing individual transmission events can be achieved by epidemiological investigation coupled with pathogen typing or genome sequencing. Individual infectiousness can be estimated by measuring pathogen loads, but few studies have directly estimated the ability of infected hosts to transmit to uninfected hosts...
July 2017: Microbiology Spectrum
https://www.readbyqxmd.com/read/28807164/effect-of-chinese-herbal-medicine-on-male-infertility
#2
Dan Jiang, Alberto Coscione, Lily Li, Bai-Yun Zeng
Male infertility normally refers a male's inability to cause pregnancy in a fertile female partner after 1 year of unprotected intercourse. Male infertility in recent years has been attracting increasing interest from public due to the evidence in decline in semen quality. There are many factors contributing to the male infertility including abnormal spermatogenesis; reproductive tract anomalies or obstruction; inadequate sexual and ejaculatory functions; and impaired sperm motility, imbalance in hormone levels, and immune system dysfunction...
2017: International Review of Neurobiology
https://www.readbyqxmd.com/read/28805017/estimating-the-between-farm-transmission-rates-for-highly-pathogenic-avian-influenza-subtype-h5n1-epidemics-in-bangladesh-between-2007-and-2013
#3
A Ssematimba, I Okike, G M Ahmed, M Yamage, G J Boender, T J Hagenaars, B Bett
Highly Pathogenic Avian Influenza (HPAI) is classified by the World Organization for Animal Health as one of the notifiable diseases. Its occurrence is associated with severe socio-economic impacts and is also zoonotic. Bangladesh HPAI epidemic data for the period between 2007 and 2013 were obtained and split into epidemic waves based on the time lag between outbreaks. By assuming the number of newly infected farms to be binomially distributed, we fit a Generalized Linear Model to the data to estimate between-farm transmission rates (β)...
August 14, 2017: Transboundary and Emerging Diseases
https://www.readbyqxmd.com/read/28803069/estimating-the-reproductive-number-total-outbreak-size-and-reporting-rates-for-zika-epidemics-in-south-and-central-america
#4
Deborah P Shutt, Carrie A Manore, Stephen Pankavich, Aaron T Porter, Sara Y Del Valle
As South and Central American countries prepare for increased birth defects from Zika virus outbreaks and plan for mitigation strategies to minimize ongoing and future outbreaks, understanding important characteristics of Zika outbreaks and how they vary across regions is a challenging and important problem. We developed a mathematical model for the 2015/2016 Zika virus outbreak dynamics in Colombia, El Salvador, and Suriname. We fit the model to publicly available data provided by the Pan American Health Organization, using Approximate Bayesian Computation to estimate parameter distributions and provide uncertainty quantification...
July 13, 2017: Epidemics
https://www.readbyqxmd.com/read/28802754/cost-benefit-analyses-of-supplementary-measles-immunisation-in-the-highly-immunized-population-of-new-zealand
#5
D T S Hayman, J C Marshall, N P French, T E Carpenter, M G Roberts, T Kiedrzynski
As endemic measles is eliminated from countries through increased immunisation, the economic benefits of enhanced immunisation programs may come into question. New Zealand has suffered from outbreaks after measles introductions from abroad and we use it as a model system to understand the benefits of catch up immunisation in highly immunised populations. We provide cost-benefit analyses for measles supplementary immunisation in New Zealand. We model outbreaks based on estimates of the basic reproduction number in the vaccinated population (Rv, the number of secondary infections in a partially immunised population), based on the number of immunologically-naïve people at district and national levels, considering both pre- and post-catch up vaccination scenarios...
August 9, 2017: Vaccine
https://www.readbyqxmd.com/read/28798323/modeling-the-transmission-and-control-of-zika-in-brazil
#6
Liping Wang, Hongyong Zhao, Sergio Muniz Oliva, Huaiping Zhu
Zika virus, a reemerging mosquito-borne flavivirus, started spread across Central and Southern America and more recently to North America. The most serious impacted country is Brazil. Based on the transmission mechanism of the virus and assessment of the limited data on the reported suspected cases, we establish a dynamical model which allows us to estimate the basic reproduction number R 0 = 2.5020. The wild spreading of the virus make it a great challenge to public health to control and prevention of the virus...
August 10, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28796232/reconstitution-of-mouse-oogenesis-in-a-dish-from-pluripotent-stem-cells
#7
Katsuhiko Hayashi, Orie Hikabe, Yayoi Obata, Yuji Hirao
This protocol is an extension to: Nat. Protoc. 8, 1513-1524 (2013); doi: 10.1038/nprot.2013.090; published online 11 July 2013Generation of functional oocytes in culture from pluripotent stem cells should provide a useful model system for improving our understanding of the basic mechanisms underlying oogenesis. In addition, it has potential applications as an alternative source of oocytes for reproduction. Using the most advanced mouse model in regard to reproductive engineering and stem cell biology, we previously developed a culture method that produces functional primorial germ cells starting from pluripotent cells in culture and described it in a previous protocol...
September 2017: Nature Protocols
https://www.readbyqxmd.com/read/28765371/zika-plasma-viral-dynamics-in-nonhuman-primates-provides-insights-into-early-infection-and-antiviral-strategies
#8
Katharine Best, Jeremie Guedj, Vincent Madelain, Xavier de Lamballerie, So-Yon Lim, Christa E Osuna, James B Whitney, Alan S Perelson
The recent outbreak of Zika virus (ZIKV) has been associated with fetal abnormalities and neurological complications, prompting global concern. Here we present a mathematical analysis of the within-host dynamics of plasma ZIKV burden in a nonhuman primate model, allowing for characterization of the growth and clearance of ZIKV within individual macaques. We estimate that the eclipse phase for ZIKV, the time between cell infection and viral production, is most likely short (∼4 h), the median within-host basic reproductive number R0 is 10...
August 15, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28762130/modelling-coupled-within-host-and-population-dynamics-of-formula-see-text-and-formula-see-text-hiv-infection
#9
Edna Chilenje Manda, Faraimunashe Chirove
Most existing models have considered the immunological processes occurring within the host and the epidemiological processes occurring at population level as decoupled systems. We present a new model using continuous systems of non linear ordinary differential equations by directly linking the within host dynamics capturing the interactions between Langerhans cells, CD4[Formula: see text] T-cells, R5 HIV and X4 HIV and the without host dynamics of a basic compartmental HIV/AIDS model. The model captures the biological theories of the cells that take part in HIV transmission...
July 31, 2017: Journal of Mathematical Biology
https://www.readbyqxmd.com/read/28761570/estimation-of-the-basic-reproduction-number-of-novel-influenza-a-h1n1-pdm09-in-elementary-schools-using-the-sir-model
#10
Daisuke Furushima, Shoko Kawano, Yuko Ohno, Masayuki Kakehashi
BACKGROUND: The novel influenza A (H1N1) pdm09 (A/H1N1pdm) pandemic of 2009-2010 had a great impact on society. OBJECTIVE: We analyzed data from the absentee survey, conducted in elementary schools of Oita City, to evaluate the A/H1N1pdm pandemic and to estimate the basic reproductive number (R0 ) of this novel strain. METHOD: We summarized the overall absentee data and calculated the cumulative infection rate. Then, we classified the data into 3 groups according to school size: small (<300 students), medium (300-600 students), and large (>600 students)...
2017: Open Nursing Journal
https://www.readbyqxmd.com/read/28757186/the-basic-reproduction-number-r0-of-measles-a-systematic-review
#11
REVIEW
Fiona M Guerra, Shelly Bolotin, Gillian Lim, Jane Heffernan, Shelley L Deeks, Ye Li, Natasha S Crowcroft
The basic reproduction number, R nought (R0), is defined as the average number of secondary cases of an infectious disease arising from a typical case in a totally susceptible population, and can be estimated in populations if pre-existing immunity can be accounted for in the calculation. R0 determines the herd immunity threshold and therefore the immunisation coverage required to achieve elimination of an infectious disease. As R0 increases, higher immunisation coverage is required to achieve herd immunity...
July 27, 2017: Lancet Infectious Diseases
https://www.readbyqxmd.com/read/28747901/could-the-recent-zika-epidemic-have-been-predicted
#12
Ángel G Muñoz, Madeleine C Thomson, Anna M Stewart-Ibarra, Gabriel A Vecchi, Xandre Chourio, Patricia Nájera, Zelda Moran, Xiaosong Yang
Given knowledge at the time, the recent 2015-2016 zika virus (ZIKV) epidemic probably could not have been predicted. Without the prior knowledge of ZIKV being already present in South America, and given the lack of understanding of key epidemiologic processes and long-term records of ZIKV cases in the continent, the best related prediction could be carried out for the potential risk of a generic Aedes-borne disease epidemic. Here we use a recently published two-vector basic reproduction number model to assess the predictability of the conditions conducive to epidemics of diseases like zika, chikungunya, or dengue, transmitted by the independent or concurrent presence of Aedes aegypti and Aedes albopictus...
2017: Frontiers in Microbiology
https://www.readbyqxmd.com/read/28742854/risk-of-exposure-to-potential-vector-mosquitoes-for-rural-workers-in-northern-lao-pdr
#13
Julie-Anne A Tangena, Phoutmany Thammavong, Steve W Lindsay, Paul T Brey
BACKGROUND: One major consequence of economic development in South-East Asia has been a rapid expansion of rubber plantations, in which outbreaks of dengue and malaria have occurred. Here we explored the difference in risk of exposure to potential dengue, Japanese encephalitis (JE), and malaria vectors between rubber workers and those engaged in traditional forest activities in northern Laos PDR. METHODOLOGY/PRINCIPAL FINDINGS: Adult mosquitoes were collected for nine months in secondary forests, mature and immature rubber plantations, and villages...
July 2017: PLoS Neglected Tropical Diseases
https://www.readbyqxmd.com/read/28741105/transmission-fitness-in-co-colonization-and-the-persistence-of-bacterial-pathogens
#14
Maria Gaivão, Francisco Dionisio, Erida Gjini
Humans are often colonized by polymorphic bacteria such as Streptococcus pneumoniae, Bordetella pertussis, Staphylococcus Aureus, and Haemophilus influenzae. Two co-colonizing pathogen clones may interact with each other upon host entry and during within-host dynamics, ranging from competition to facilitation. Here we examine the significance of these exploitation strategies for bacterial spread and persistence in host populations. We model SIS epidemiological dynamics to capture the global behavior of such multi-strain systems, focusing on different parameters of single and dual colonization...
July 24, 2017: Bulletin of Mathematical Biology
https://www.readbyqxmd.com/read/28735086/a-series-of-population-models-for-hyphantria-cunea-with-delay-and-seasonality
#15
Haixia Lu, Haitao Song, Huaiping Zhu
In this paper, we establish and study a basic stage-structured model for the population of Hyphantria cunea, a delay differential equation model and a model incorporating the resource and seasonality. By introducing the population reproduction number R0, we show that R0 acts as a threshold parameter for the existence and stability of equilibria. The trivial equilibria of the above models are all globally asymptotically stable when R0<1; the basic model and the delay-differential model have a unique positive equilibrium respectively, and they are both locally asymptotically stable when R0>1; the model with periodic season is uniformly persistent and admits a positive periodic solution if R0>1...
July 19, 2017: Mathematical Biosciences
https://www.readbyqxmd.com/read/28723920/temperature-modulates-dengue-virus-epidemic-growth-rates-through-its-effects-on-reproduction-numbers-and-generation-intervals
#16
Amir S Siraj, Rachel J Oidtman, John H Huber, Moritz U G Kraemer, Oliver J Brady, Michael A Johansson, T Alex Perkins
Epidemic growth rate, r, provides a more complete description of the potential for epidemics than the more commonly studied basic reproduction number, R0, yet the former has never been described as a function of temperature for dengue virus or other pathogens with temperature-sensitive transmission. The need to understand the drivers of epidemics of these pathogens is acute, with arthropod-borne virus epidemics becoming increasingly problematic. We addressed this need by developing temperature-dependent descriptions of the two components of r-R0 and the generation interval-to obtain a temperature-dependent description of r...
July 2017: PLoS Neglected Tropical Diseases
https://www.readbyqxmd.com/read/28716140/modelling-infectious-diseases-with-relapse-a-case-study-of-hsv-2
#17
Jinliang Wang, Xiaoqing Yu, Heidi L Tessmer, Toshikazu Kuniya, Ryosuke Omori
BACKGROUND: Herpes Simplex Virus Type 2 (HSV-2) is one of the most common sexually transmitted diseases. Although there is still no licensed vaccine for HSV-2, a theoretical investigation of the potential effects of a vaccine is considered important and has recently been conducted by several researchers. Although compartmental mathematical models were considered for each special case in the previous studies, as yet there are few global stability results. RESULTS: In this paper, we formulate a multi-group SVIRI epidemic model for HSV-2, which enables us to consider the effects of vaccination, of waning vaccine immunity, and of infection relapse...
July 17, 2017: Theoretical Biology & Medical Modelling
https://www.readbyqxmd.com/read/28703921/estimating-and-modelling-the-transmissibility-of-middle-east-respiratory-syndrome-corona-virus-during-the-2015-outbreak-in-the-republic-of-korea
#18
Xu-Sheng Zhang, Richard Pebody, Andre Charlett, Daniela de Angelis, Paul Birrell, Hunseok Kang, Marc Baguelin, Yoon Hong Choi
BACKGROUND: Emerging respiratory infections represent a significant public health threat. Because of their novelty, there are limited measures available to control their early spread. Learning from past outbreaks is important for future preparation. The MERS-CoV 2015 outbreak in the Republic of Korea (ROK) provides one such opportunity. OBJECTIVES: We demonstrated through quantitative methodologies how to estimate MERS-CoV's transmissibility and identified the effective countermeasures that stopped its spread...
July 13, 2017: Influenza and Other Respiratory Viruses
https://www.readbyqxmd.com/read/28694450/modelling-west-nile-virus-transmission-risk-in-europe-effect-of-temperature-and-mosquito-biotypes-on-the-basic-reproduction-number
#19
Chantal B F Vogels, Nienke Hartemink, Constantianus J M Koenraadt
West Nile virus (WNV) is a mosquito-borne flavivirus which has caused repeated outbreaks in humans in southern and central Europe, but thus far not in northern Europe. The main mosquito vector for WNV, Culex pipiens, consists of two behaviourally distinct biotypes, pipiens and molestus, which can form hybrids. Differences between biotypes, such as vector competence and host preference, could be important in determining the risk of WNV outbreaks. Risks for WNV establishment can be modelled with basic reproduction number (R 0) models...
July 10, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28691034/the-effects-of-time-lag-and-cure-rate-on-the-global-dynamics-of-hiv-1-model
#20
Nigar Ali, Gul Zaman, Abdullah, Aisha M Alqahtani, Ali Saleh Alshomrani
In this research article, a new mathematical model of delayed differential equations is developed which discusses the interaction among CD4 T cells, human immunodeficiency virus (HIV), and recombinant virus with cure rate. The model has two distributed intracellular delays. These delays denote the time needed for the infection of a cell. The dynamics of the model are completely described by the basic reproduction numbers represented by R0, R1, and R2. It is shown that if R0 < 1, then the infection-free equilibrium is locally as well as globally stable...
2017: BioMed Research International
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