An SIS epidemiology game with two subpopulations

There is significant current interest in the application of game theory to problems in epidemiology. Most mathematical analyses of epidemiology games have studied populations where all individuals have the same risks and interests. This paper analyses the rational-expectation equilibria in an epidemiology game with two interacting subpopulations of equal size where decisions change the prevalence and transmission patterns of an infectious disease. The transmission dynamics are described by an SIS model and individuals are only allowed to invest in daily prevention measures like hygiene. The analysis shows that disassortative mixing may lead to multiple Nash equilibria when there are two interacting subpopulations affecting disease prevalence. The dynamic stability of these equilibria is analysed under the assumption that strategies change slowly in the direction of self-interest. When mixing is disassortative, interior Nash equilibria are always unstable. When mixing is positively assortative, there is a unique Nash equilibrium that is globally stable.     

An SIS epidemiology game with two subpopulations

There is significant current interest in the application of game theory to problems in epidemiology. Most mathematical analyses of epidemiology games have studied populations where all individuals have the same risks and interests. This paper analyses the rational-expectation equilibria in an epidemiology game with two interacting subpopulations of equal size where decisions change the prevalence and transmission patterns of an infectious disease. The transmission dynamics are described by an SIS model and individuals are only allowed to invest in daily prevention measures like hygiene. The analysis shows that disassortative mixing may lead to multiple Nash equilibria when there are two interacting subpopulations affecting disease prevalence. The dynamic stability of these equilibria is analysed under the assumption that strategies change slowly in the direction of self-interest. When mixing is disassortative, interior Nash equilibria are always unstable. When mixing is positively assortative, there is a unique Nash equilibrium that is globally stable.     

Molecular epidemiology of infectious diseases

Data on molecular epidemiology of bacterial infections is summarized. The term definitions of "molecular epidemiology", "taxonomic species" are given, the limits and species structure of prokaryotes are described. The basic mechanisms of the prokaryotes variability in the epidemic process, as well as the possibilities and limitations of microbiological, molecular-biological and population--genetic typing methods, are characterized. The tactics of molecular-biological studies in analyzing the population structure on the global, regional and local levels is presented. The economic effectiveness of measures taken with due consideration of information on the clonal structure of causative agents of hospital infections is shown.     

Pools versus Queues: The Variable Dynamics of Stochastic “Steady States”

Mathematical models in ecology and epidemiology often consider populations “at equilibrium”, where in-flows, such as births, equal out-flows, such as death. For stochastic models, what is meant by equilibrium is less clear – should the population size be fixed or growing and shrinking with equal probability? Two different mechanisms to implement a stochastic steady state are considered. Under these mechanisms, both a predator-prey model and an epidemic model have vastly different outcomes, including the median population values for both predators and prey and the median levels of infection within a hospital (P < 0.001 for all comparisons). These results suggest that the question of how a stochastic steady state is modeled, and what it implies for the dynamics of the system, should be carefully considered.     

Schistosoma intercalatum: an endangered species in Cameroon?

Despite the extremely wide distribution of both intermediate (snail) and definitive hosts, the species Schistosoma intercalatum has a highly restricted distribution in parts of West Africa (Cameroon, Equatorial Guinea, Gabon, Nigeria, Democratic Republic of Congo and S?o Tomé). Recent studies showed that the epidemiology of this species is very dynamic, including invasions and extinctions. This article reviews the epidemiology of S. intercalatum in Cameroon, where the species is endangered, and analyses its overall status in Africa. The possible reasons for the limited distribution of S. intercalatum are discussed.     

Cell population-based framework of genetic epidemiology in the single-cell omics era

Genetic epidemiology is a rapidly advancing field due to the recent availability of large amounts of omics data. In recent years, it has become possible to obtain omics information at the single-cell level, so genetic epidemiological models need to be updated to integrate with single-cell expression data. In this perspective paper, we propose a cell population-based framework for genetic epidemiology in the single-cell era. In this framework, genetic diversity influences phenotypic diversity through the diversity of cell population profiles, which are defined as high-dimensional probability distributions of the state spaces of biomolecules of each omics layer. We discuss how biomolecular experimental measurement data can capture the different properties of this distribution. In particular, single-cell data constitute a sample from this population distribution where only some coordinate values are observable. From a data analysis standpoint, we introduce methodology for feature extraction from cell population profiles. Finally, we discuss how this framework can be applied not only to genetic epidemiology but also to systems biology.     

Human herpesvirus 8: an update

The discovery of human herpesvirus 8 (HHV-8) has opened a new field in the biology and in the clinical definition of HHV-8-associated diseases. Various aspects of epidemiology, laboratory diagnosis and treatment of HHV-8 infection are still controversial. This review will summarise the most recent findings on the modalities of viral transmission in geographic areas where the virus is endemic as compared with those where the infection is sporadic. The studies on the interactions between HHV-8 and Epstein-Barr virus in the promotion of tumorigenesis will be then emphasised. This review will finally address the problems still open in the laboratory diagnosis and in the definition of antiviral drug susceptibility of HHV-8. Solving satisfactorily these issues will be necessary to better understand the epidemiology of HHV-8 infection, to reduce the risk of viral transmission, the progression of infected hosts to HHV-8-related malignancies and to achieve more active treatment options for these clinical conditions.     

Persistence of carbapenem-resistant Acinetobacter baumannii strains in an Italian intensive care unit during a forty-six month study period

The aims of this study were to analyze carbapenem-resistance Acinetobacter baumannii isolates (CRAB) and their molecular epidemiology in an ICU of Southern Italy. Clinical outcomes and therapeutic management of patients are also described. The study was performed from January 2007 to October 2010. The presence of carbapenemases was determined by PCR. Strains were typed by PFGE. All A. baumannii isolates were carbapenem-resistant with imipenem MIC≥16 μg/mL. Molecular characterization showed the occurrence of a predominant clone. The most frequent infection by CRAB was ventilator-associated pneumonia; colistin was the drug of choice for this infection. The therapy was safe in all cases except in one where therapy was suspended due to the onset of acute renal failure. We documented the presence of CRAB in this ICU, besides the occurrence of a predominant clone, over all the study period. Despite the infection control procedures used, intra-facility A. baumannii transmission is evident as well as the significant capacity for long-term survival in the hospital environment.     

A brief history of R0 and a recipe for its calculation

In 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 populations.     

RAPD-fingerprinting of Serratia marcescens after formaldehyde inactivation of DNase activity

Serratia marcescens strains commonly cause hospital outbreaks. A random amplified polymorphic DNA (RAPD) assay was applied to the epidemiology of Ser. marcescens using formaldehyde fixation and boiling of bacterial cells for DNA extraction. The method preserved bacterial DNA and gave optimal results of RAPD-fingerprinting, facilitating the investigation of hospital infections caused by Ser. marcescens.     

Therapeutic approach to Staphylococcus aureus bacteremia

Staphylococcus aureus is an important human pathogen, responsible for 11-33% of the bacteremias acquired in the hospital setting and nearly 50% of those acquired in the community at large. The epidemiology of S. aureus bacteremia is discussed, with an special emphasis on the situation in Colombia and the resistance mechanisms against the major drug groups used for the treatment. The clinical keys and laboratory support for the appropriate clinical approaches are presented together with the therapeutic strategies for the treatment of patients with S. aureus bacteremia.     

In the Eastern Townships,Province of Quebec: Occurrence of Pneumocystosis

Three cases of pneumocystosis which occurred in the Quebec Eastern Townships are reported. It seems that in Canada such cases are concentrated in that province. The number of infections caused by this micro-organism is steadily rising and at the present time more cases are reported from Canada and the United States than from Europe. In most cases these patients, children as well as adults, are suffering from an immunologic defect. The authors review morphology, epidemiology and the relationship between host and infecting micro-organism. Clinical diagnosis is possible. Identification of asymptomatic carriers is important, particularly among hospital staff working in nurseries, transplant units and with patients whose condition lowers their immunologic resistance.     

The effects of shifts and drifts on the epidemiology of influenza in man

Accurate information on the epidemiology of influenza over the World is difficult to obtain as it is dependent on both national statistics of morbidity and mortality and on adequate virological confirmation of suspected cases. Only a few countries have the facilities for these and in much of the World it is difficult to establish exactly the impact of influenza. For this reason, our knowledge on the natural history of the disease and the virus causing it is restricted to what happens in a few areas of the World where the necessary information is obtainable. In one of these areas, the U.K., it has been possible to follow the appearance of influenza in successive years throughout the 11 years of prevalence of the H2N2 virus and throughout the 10 years of prevalence of the H3N2 virus. What are still unknown are the factors that determine this pattern. Various hypotheses have been proposed to explain the epidemiology of influenza.     

Do hookworms elicit protective immunity in man?

The two main species of human hookworm, Ancylostoma duodenale and Necator americanus (Table 1), are together believed to infect about 900 million people - mainly in tropical countries where adequate sanitary facilities may be lacking. But interactions between the two species, and their relative contributions to observed age-related infection patterns and seasonal cycles of transmission, continue to engender controversy. People tend to remain susceptible to infection through-out life, even with constant exposure to the infective stages. So what role does human immunity or resistance play in the epidemiology and control of infection? In this article, Jerzy Behnke reviews the epidemiology of hookworm infection in the light of current understanding of mechanisms involved in host responses to infection and hookworm evasion of those responses. As he stresses, much further work is required.     

Molecular epidemiology of infections caused by methicillin-resistant staphylococci

The review deals with the periodicity of the spread of methicillin-resistant S. aureus (MRSA) strains during the last 40 years, the mechanism of their resistance to methicillin and other beta-lactamic antibiotics, the genetic control of methicillin resistance, the genome organization of mec DNA and its possible cause, as well as the organization of epidemiological surveillance on MSRA in hospitals. The problem of changes in the epidemiology of staphylococcal infections due to the appearance of MRSA in the absence of contacts with carriers, treatment with antibiotics or stay in a hospital is discussed. The concern of public health authorities in connection with the emergence of MRSA strains, moderately resistant or resistant to vancomycin, is also discussed. The most promising programs of the MRSA study, as well as the optimum programs introduced in economically developed counties for the control of hospital infections caused by MRSA, are considered.     

生物样本库及其伦理问题简介

随着分子和基因组信息对流行病学影响的增加,无数遗传流行病学研究和后人类基因组计划的研究都越来越依赖人类生物样本库的使用。生物样本库的范围也已横跨学术或者医院环境下的小数量收集到大规模的全国性储藏。尽管生物样本库的概念并不新,但是在基因组研究和后人类基因组计划的背景下,伴随它们十几年极大发展的是无数待解决的伦理挑战。从生物样本库的概念着手,介绍了其与一般遗传数据库的区别以及建立生物样本库的意义;然后介绍并比较国际上已有的生物样本库,以及其伦理问题和伦理法律框架的发展趋势。     

Molecular epidemiology: potential impacts on the assessment of public health

In trying to decide what type of scientific paper I could prepare as a tribute to Jim Neel, I thought back over the discussions that we had over some 25 years. Sometimes these discussions were on specific topics such as how to extrapolate from mutation data in mice to those for humans following radiation or chemical exposures. On other occasions, our discussions were of a more philosophical nature, particularly on where the field of epidemiology might or needed to go. For example, what types of data are needed for assessing the public health impact of exposure to environmental agents. Perhaps because I enjoyed these discussions so much, I have chosen to take a look from a current perspective at the field of molecular epidemiology. Jim Neel would have loved to have entered into this discussion; he would have enhanced it in is own inimitable way.     

戊型肝炎病毒研究新进展

戊型肝炎病毒(hepatitis E virus,HEV)是引起全球多地区大规模流行和散发病例的急性病毒性肝炎的病原体,发展中国家尤为突出;我国是戊型肝炎(hepatitis E,HE)流行的高发区.HE是一种人畜共患病,猪是人HEV病毒的主要储库,因而HE已成为一个全球性的的公共卫生问题.对HEV的病毒学和基因组特征、临床表征、流行病学、主要抗原表位以及HEV诊断试剂和疫苗研制的进展进行了综述.     

The prospect of eliminating malaria transmission in some regions of Brazil

This paper discusses malaria epidemiology and control in Brazil as well as the prospect of interrupting transmission in some areas of the country. The concepts of receptivity and vulnerability of an area to malaria transmission are analysed to predict where elimination might occur in a near future. Outside of the Amazon Region and in the oriental states of the Amazon, such as Tocantins, Maranh?o and Mato Grosso, it is likely that malaria transmission can be eliminated with the development and sustained use of a good surveillance system.     

耳念珠菌的流行病学和生物学研究进展

耳念珠菌Candida auris已成为引起严重院里感染的新兴病原真菌。自2009年第一次报道以来,耳念珠菌在全球迅速传播并导致几次院内感染的暴发。与念珠菌属其他成员相比,耳念珠菌具有诸多特点,比如多重耐药、鉴别困难、死亡率高、易在医院内传播等。关于耳念珠菌的生物学和致病性研究越来越多,我们对耳念珠菌的认识也逐渐增强,本综述详细地介绍了耳念珠菌全球感染的流行病学以及该病原真菌的基本生物学特征,并对其毒力和耐药机制研究进展进行汇总,对未来关于耳念珠菌研究的前景进行了展望。