The effect of cultivation on the size, shape, and persistence of disease patches in fields

Epidemics of soil-borne plant disease are characterized by patchiness because of restricted dispersal of inoculum. The density of inoculum within disease patches depends on a sequence comprising local amplification during the parasitic phase followed by dispersal of inoculum by cultivation during the intercrop period. The mechanisms that control size, shape, and persistence have received very little rigorous attention in epidemiological theory. Here we derive a model for dispersal of inoculum in soil by cultivation that takes account into the discrete stochastic nature of the system in time and space. Two parameters, probability of movement and mean dispersal distance, characterize lateral dispersal of inoculum by cultivation. The dispersal parameters are used in combination with the characteristic area and dimensions of host plants to identify criteria that control the shape and size of disease patches. We derive a critical value for the probability of movement for the formation of cross-shaped patches and show that this is independent of the amount of inoculum. We examine the interaction between local amplification of inoculum by parasitic activity and subsequent dilution by dispersal and identify criteria whereby asymptomatic patches may persist as inoculum falls below a threshold necessary for symptoms to appear in the subsequent crop. The model is motivated by the spread of rhizomania, an economically important soil-borne disease of sugar beet. However, the results have broad applicability to a very wide range of diseases that survive as discrete units of inoculum. The application of the model to patch dynamics of weed seeds and local introductions of genetically modified seeds is also discussed.

Impact of vaccination on the spatial correlation and persistence of measles dynamics.

The onset of measles vaccination in England and Wales in 1968 coincided with a marked drop in the temporal correlation of epidemic patterns between major cities. We analyze a variety of hypotheses for the mechanisms driving this change. Straightforward stochastic models suggest that the interaction between a lowered susceptible population (and hence increased demographic noise) and nonlinear dynamics is sufficient to cause the observed drop in correlation. The decorrelation of epidemics could potentially lessen the chance of global extinction and so inhibit attempts at measles eradication.

Emergence of a new epidemic/epizootic Venezuelan equine encephalitis virus in South America.

One of the most important questions in arbovirology concerns the origin of epidemic Venezuelan equine encephalitis (VEE) viruses; these viruses caused periodic, extensive epidemics/epizootics in the Americas from 1938-1973 (reaching the United States in 1971) but had recently been presumed extinct. We have documented the 1992 emergence of a new epidemic/epizootic VEE virus in Venezuela. Phylogenetic analysis of strains isolated during two outbreaks indicated that the new epidemic/epizootic virus(es) evolved recently from an enzootic VEE virus in northern South America. These results suggest continued emergence of epizootic VEE viruses; surveillance of enzootic viruses and routine vaccination of equines should therefore be resumed.

La importancia del higienismo y la potabilización del agua en la ciudad de Valencia (1860-1910)

El siglo XIX se caracteriza por numerosos cambios tanto a nivel social como estructural de la población: se produce un acelerado desarrollo urbano sin planificación y carente de servicios que da lugar a una mala calidad de vida y numerosas epidemias. Estos cambios tienen como resultado un nuevo movimiento, el Higienismo, que pretende mejorar las condiciones de vida de la población. En España, todas las reformas higiénicas se desarrollaron mediante los planes de Ensanche. Uno de los puntos clave de este pensamiento es el abastecimiento de agua potable como medio para evitar enfermedades. La ciudad de Valencia es un claro ejemplo de la importancia de este movimiento y cómo el abastecimiento de agua es un elemento clave en la mejora de la calidad de vida de las personas.

Student notes from medical lectures by Benjamin Rush, undated

The volumes contain student notes on a course of medical lectures given by Dr. Benjamin Rush (1746-1813) while he was Professor of the Institutes of Medicine and Clinical Practice at the University of Pennsylvania Medical School, likely in circa 1800-1813. The notes indicate Rush often referenced the works or teachings of contemporaries such as Scottish physicians William Cullen, John Brown, John Gregory, and Robert Whytt, and Dutch physician Herman Boerhaave. He frequently included anecdotes and case histories of his own patients, as well as those of other doctors, to illustrate his lecture topics. He also advised students to take notes on the lectures after they ended to allow them to focus on what they were hearing. Volume 1 includes notes on: physician conduct during visits to patients; human and animal physiology; voice and speech; the nervous system; the five senses; and faculties of the mind. Volume 2 includes notes on: food, the sources of appetite and thirst, and digestion; the lymphatic system; secretions; excretions; theories of nutrition; differences in the minds and bodies of women and men; reproduction; pathology; a table outlining the stages of disease production; “disease and the origin of moral and natural evil”; contagions; the role of food, drink, and clothing in producing disease; worms; hereditary diseases; predisposition to diseases; proximate causes of diseases; and pulmonary conditions. Volume 3 includes notes on: the pulse; therapeutics, such as emetics, sedatives, and digitalis, and treatment of various illnesses like pulmonary consumption, kidney disease, palsy, and rheumatism; diagnosis and prognosis of fever; treatment of intermitting fever; and epidemics including plague, smallpox, and yellow fever, with an emphasis on the yellow fever outbreaks in Philadelphia in 1793 and 1797.

Demographic situation in Russia. OSW Study 24/2006

Throughout the history of Russia, periods of deep chaos have been accompanied by demographic crises. This was the case during the Time of Troubles, or Smutnoye Vremya, in the seventeenth century, and during the period of wars and revolutions in the early twentieth century, which brought the Bolsheviks to power. Similarly, the break-up of the USSR also coincided with a demographic crisis. However, while the previous crises had been caused by factors such as war, famine, epidemics or repressive policies, and were followed by periods of rapid population growth once these factors had ceased to operate, the current crisis is systemic and structural. To a large extent, it has been occasioned by cultural factors such as changing family models and the roles of women in today's society. In Russia, the effect of these factors on population increase is exacerbated by excessive alcohol consumption, an culture of inadequate working conditions which leads to many accidents at work, and healthcare deficiencies (only c. 3% of the GDP is spent on healthcare annually).

The effect of extreme cold temperatures on the risk of death in the two major Portuguese cities

It is well known that meteorological conditions influence the comfort and human health. Southern European countries, including Portugal, show the highest mortality rates during winter, but the effects of extreme cold temperatures in Portugal have never been estimated. The objective of this study was the estimation of the effect of extreme cold temperatures on the risk of death in Lisbon and Oporto, aiming the production of scientific evidence for the development of a real-time health warning system. Poisson regression models combined with distributed lag non-linear models were applied to assess the exposure-response relation and lag patterns of the association between minimum temperature and all-causes mortality and between minimum temperature and circulatory and respiratory system diseases mortality from 1992 to 2012, stratified by age, for the period from November to March. The analysis was adjusted for over dispersion and population size, for the confounding effect of influenza epidemics and controlled for long-term trend, seasonality and day of the week. Results showed that the effect of cold temperatures in mortality was not immediate, presenting a 1–2-day delay, reaching maximumincreased risk of death after 6–7 days and lasting up to 20–28 days. The overall effect was generally higher and more persistent in Lisbon than in Oporto, particularly for circulatory and respiratory mortality and for the elderly. Exposure to cold temperatures is an important public health problem for a relevant part of the Portuguese population, in particular in Lisbon.

AIDS and the historian : proceedings of a conference at the National Institutes of Health, 20-21 March 1989 /

"Sponsors: National Heart, Lung, and Blood Institute, ... [et al.]"

D. Nicolai Francisci de San Iuan et Domingo ... De morbis endemis Caesar-Augustae : opus pro ineuntibus praxim, veram et tutam medendi viam ostendens ...

Mode of access: Internet.

Tratado de las epidemias malignas, y enfermedades particulares de los exercitos, con advertencias á sus capitanes generales, ingenieros, medicos, y cirujanos ... /

Mode of access: Internet.

Petri Francisci Phrygii ... Commentarii in Historias epidemicas Hippocratis : in tres partes digesti : opus omnibus medicinae studiosis vtilissimum

Mode of access: Internet.

Hyppocratis epidemialium observationum pars prima : quatuor contenta languentibus : in qua ne dum praxis methodica, cum auxiliis legitur, sed etiam multa quaestiones, philosophis, ac medicis utilissime, proponuntur /

Mode of access: Internet.

Relacion de las epidemias, que han afligido a la ciudad de Cartagena, sus causas y metodo curativo arreglado à los mas celebres Autores ... /

Mode of access: Internet.

Disputa epidemica : teatro racional donde desnuda la verdad se presenta al examen de los ingenios : thesis en que se ventila el vso de los alexifarmacos sudorificos en el principio de las malignas del año de 84 /

Mode of access: Internet.

Disputa epidemica : teatro racional donde desnuda la verdad se presenta al examen de los ingenios : thesis en que se ventila el vso de los alexifarmacos sudorificos en el principio de las malignas del año de 84 /

Mode of access: Internet.