1,721,148 research outputs found
On stochastic models for the spread of infections
Get PDFHeesterbeek, J.A.P. [Promotor]Meester, R.W.J. [Promotor
The metapopulation dynamics of an infectious disease: a case study of tuberculosis in possums
No full textAn SEI metapopulation model is developed for the spread of an infectious agent by migration. The
model portrays two age classes on a number of patches connected by migration routes which are
used as host animals mature. A feature of this model is that the basic reproduction ratio may be
computed directly, using a scheme that separates topography, demography, and epidemiology. We
also provide formulas for individual patch basic reproduction numbers and discuss their connection
with the basic reproduction ratio for the system. The model is applied to the problem of spatial
spread of bovine tuberculosis in a possum population. The temporal dynamics of infection are
investigated for some generic networks of migration links, and the basic reproduction ratio is
computed—its value is not greatly different from that for a homogeneous model. Three scenarios
are considered for the control of bovine tuberculosis in possums where the spatial aspect is shown
to be crucial for the design of disease management operations
How to estimate the efficacy of control of an infectious plant disease
Get PDFCertain infectious plant diseases are controlled by inspection and subsequent hand removal of diseased parts. In this paper we give two sets of criteria from which one can conclude whether this control effort is adequate or not. These criteria do not require knowledge of the infection- or detection rate of the disease but only use the structure of the contact matrix. Computer experiments give a feeling of how many inspections are needed in order to draw a conclusion
The saturating contact rate in marriage and epidemic models
Get PDFIn this note we show how to derive, by a mechanistic argument, an expression for the saturating contact rate of individual contacts in a population that mixes randomly. The main assumption is that the individual interaction times are typically short as compared to the time-scale of changes in, for example, individual-type, but that the interactions yet make up a considerable fraction of the time-budget of an individual. In special cases an explicit formula for the contact rate is obtained. The result is applied to mathematical epidemiology and marriage models
Facing dengue in pediatrics: studies in a highly endemic region: Dengue in pediatrics
No full textAn overview of dengue epidemiology in Indonesia over 45 years showed an increase in dengue infections in the adolescent age group since 1999. Clinical and laboratory manifestations in children were mostly fever, petechiae, epistaxis, hepatomegaly, and thrombocytopenia. Encephalopathy and gastrointestinal bleeding were found only in dengue shock syndrome (DSS). Subsequent study demonstrated that in our tertiary care hospital, one third of hospitalized children with dengue fever progressed to DSS, and of dengue hemorrhagic fever (DHF) cases, 6% progressed to DSS. Only fever duration was significantly associated with clinical progression, suggesting that the disease course of dengue in children is predictable and stressing the importance of close clinical monitoring of patients. Further study of the profile and clinical signs in infants with confirmed dengue in a 10-year period showed that two strong indicators of DSS in infants were liver enlargement and fluid accumulation. Diarrhea and cough as atypical clinical presentations were found in one third of dengue in infants. The diagnostic value of warning signs in different age groups of children was also explored, to help clinicians facing dengue in endemic countries. Infants with the warning signs of liver enlargement and clinical fluid accumulation are more likely to progress to severe dengue, while in younger children and adolescents, the warning signs are firstly an increase in hematocrit with concurrent rapid decrease in platelet count, followed by abdominal pain, vomiting, or fluid accumulation. A long-term follow-up study of pediatric DHF patients assessed Carotid intima-media thickness (cIMT) and arterial stiffness to detect preclinical atherosclerosis, comparing a post-DHF group and a control group. The result showed no differences in arterial stiffness; longer follow-up studies are warranted
On the definition and the computation of the basic reproduction ratio R0 in models for infectious diseases in heterogeneous populations.
No full textThe expected number of secondary cases produced by a typical infected individual during its entire period of infectiousness in a completely susceptible population is mathematically defined as the dominant eigenvalue of a positive linear operator. It is shown that in certain special cases one can easily compute or estimate this eigenvalue. Several examples involving various structuring variables like age, sexual disposition and activity are presented
A brief history of R0 and a recipe for its calculation
No full textIn this paper I present the genesis of R 0 in demography, ecology and epidemiology, from embryo to its current adult form. I argue on why it has taken so long for the concept to mature in epidemiology when there were ample opportunities for cross-fertilisation from demography and ecology from where it reached adulthood fifty years earlier. Today, R 0 is a more fully developed adult in epidemiology than in demography. In the final section I give an algorithm for its calculation in heterogeneous population
A brief history of Ro and a recipe for its calculation
No full textIn this paper I present the genesis of R0 in demography, ecology and epidemiology, from embryo to its current adult form. I argue on why it has taken so long for the concept to mature in epidemiology when there were ample opportunities for cross-fertilisation from demography and ecology from where it reached adulthood fifty years earlier. Today, R0 is a more fully developed adult in epidemiology than in demography. In the final section I give an algorithm for its calculation in heterogeneous populations
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