The system of epidemiological surveillance as a reflection of the structure of the epidemic process

The socio-ecological concept in epidemiology, formulated by the author in his earlier works and regarding the epidemic process as a biosocial hierarchical, integral system, can serve as a theoretical basis for the epidemiological surveillance of infectious and parasitic diseases. In accordance with the structure of the epidemic process, the system of epidemiological surveillance is subdivided into the following monitoring levels: molecular, microbiological, clinical, biocenological, statistical and sociological. The functions of epidemiological surveillance should be performed by the existing and newly organized All-Union Centers for the corresponding nosological forms.     

Seasonal infectious disease epidemiology

Seasonal change in the incidence of infectious diseases is a common phenomenon in both temperate and tropical climates. However, the mechanisms responsible for seasonal disease incidence, and the epidemiological consequences of seasonality, are poorly understood with rare exception. Standard epidemiological theory and concepts such as the basic reproductive number R0 no longer apply, and the implications for interventions that themselves may be periodic, such as pulse vaccination, have not been formally examined. This paper examines the causes and consequences of seasonality, and in so doing derives several new results concerning vaccination strategy and the interpretation of disease outbreak data. It begins with a brief review of published scientific studies in support of different causes of seasonality in infectious diseases of humans, identifying four principal mechanisms and their association with different routes of transmission. It then describes the consequences of seasonality for R0, disease outbreaks, endemic dynamics and persistence. Finally, a mathematical analysis of routine and pulse vaccination programmes for seasonal infections is presented. The synthesis of seasonal infectious disease epidemiology attempted by this paper highlights the need for further empirical and theoretical work.     

Discussion on the problems of general epidemiology

The key problems of general epidemiology: the subject, method, causality in the epidemic process, the main categories and laws, the systematization of infectious pathology and epidemiological terminology are under discussion. It is at this stage when students should form valid notions, well grounded on scientific facts and practical experience, concerning the epidemiology of noninfectious diseases with due regard to the existing differences in the interpretation of the causes of the epidemic process in noninfectious diseases and to the characteristic distribution of noninfectious diseases among the population under the influence of environmental factors without any participation of parasitic systems. The review of the notion apparatus of the theoretical epidemiology and putting it in order in accordance with general biological concepts are proposed in connection with the necessity of differentiation between the epidemic process proper (in cases of anthroponosis) and the epidemic manifestations of epizoonotic and epiphytotic processes (in cases of zoonoses and sapronoses).     

Surveillance of bacterial pathogens associated with acute diarrheal disease in the Republic of Korea during one year, 2003

An epidemiological survey of human enterobacterial infections was conducted to determine the prevalence of enteropathogens in the Republic of Korea during one year, 2003. We tested for infectious diseases in 26,992 stool samples obtained from people who visited clinics located in six big cities and six rural provinces. From these samples, we isolated 1,291 cases of enteritis bacterial infection (4.8%). In the urban areas, 821 cases of bacterial infection (6.4%) were identified and, in the rural areas, 479 bacterial strains (3.3%) were isolated. Seasonal patterns were seen for diarrhea associated with S. aureus, E. coli and V. parahaemolyticus, while Salmonella and Shigella infections showed slight seasonal variation. We found that S. aureus and Salmonella were more frequently isolated from children and the elderly; however, the prevalence of E. coli, V. parahaemolyticus, and Shigella were similar in different age groups. Routine monitoring of these infections is considered a worthwhile means by which to elucidate their epidemiology and modes of transmission and ultimately to control them more effectively. Continuous laboratory-based surveillance for findings of enteritis bacterial infection should be emphasized in the prevention of these infections.     

Measured voluntary avoidance behaviour during the 2009 A/H1N1 epidemic

Managing infectious disease is among the foremost challenges for public health policy. Interpersonal contacts play a critical role in infectious disease transmission, and recent advances in epidemiological theory suggest a central role for adaptive human behaviour with respect to changing contact patterns. However, theoretical studies cannot answer the following question: are individual responses to disease of sufficient magnitude to shape epidemiological dynamics and infectious disease risk? We provide empirical evidence that Americans voluntarily reduced their time spent in public places during the 2009 A/H1N1 swine flu, and that these behavioural shifts were of a magnitude capable of reducing the total number of cases. We simulate 10 years of epidemics (2003–2012) based on mixing patterns derived from individual time-use data to show that the mixing patterns in 2009 yield the lowest number of total infections relative to if the epidemic had occurred in any of the other nine years. The World Health Organization and other public health bodies have emphasized an important role for ‘distancing’ or non-pharmaceutical interventions. Our empirical results suggest that neglect for voluntary avoidance behaviour in epidemic models may overestimate the public health benefits of public social distancing policies.     

Some remarks on definition and validity of terms used in models for infectious disease spread.

The epidemiology of infectious diseases makes use of a number of terms, such as exposure, infected, carrier, attack rate, and immunity. Researchers who intend to model the spread of epidemics should be aware of the problems with some of these terms. The role played by inapparent, or subclinical, infections is receiving increased attention in infectious disease epidemiology. Patients with such infections may never be reported as cases, which could give rise to problems when, for example, data from national surveillance bodies are being used for modeling. The assignment of patients to different transmission groups must, in most cases, rely on self-reported data from the medical interview. This possible source of bias should be recognized.     

糖尿病流行病学研究策略及分子遗传学研究进展

流行病学是现代医学的一门重要的基础学科,也是一门应用广泛的应用学科。流行病学作为方法学在复杂疾病研究中有不可替代的作用。糖尿病具有复杂疾病属性,应该以系统的多层次的流行病学方法为研究策略。本文从流行病学与临床医学、遗传学及分子生物学交叉所形成的分支学科--临床流行病学、遗传流行病学及分子流行病学三个方面对糖尿病的研究进展作一综述,并从分子遗传学角度列举了部分糖尿病的候选基因。提出糖尿病的研究应该从宏观流行病学(如社会环境等因素的影响)和微观流行病学(如分子遗传等)结合系统地进行研究。     

Nosocomial infections in the pediatric intensive care unit

Nosocomial (hospital-acquired) infections are a major complication of serious illnesses. Severely ill patients have a greater risk of acquiring nosocomial infections, so this problem is greatest in intensive care units. Studies have demonstrated that nosocomial infections are largely preventable. Adherence to recommended techniques for patient care will have the greatest benefit in the intensive care unit. In this paper the background epidemiology of nosocomial infections is reviewed and related to pediatrics and intensive care units. Types of diseases, assistance equipment, and monitoring devices which are associated with a high risk of nosocomial infections are emphasized and specific steps for lowering this risk are listed.     

On the epidemiological situation in quarantine, natural focal and other infections on the territory of the Southern Federal District

The data on the sanitary and epidemiological situation in the Southern Federal District are presented. The analysis of morbidity in tuberculosis, measles, HIV infection, viral hepatitis A, typhoid fever, cholera and quarantine infections, Crimean hemorrhagic fever, West Nile fever, rabies, malaria has been carried out. Special attention has been given to "new and newly returning infections", and among them to the spread of SARS ("atypical pneumonia"). The role of regional epidemiological safety programs, in particular such program as "The prophylaxis of quarantine and natural focal infections and the sanitary protection of the territory of the Southern Federal District of the Russian Federation from the import and spread infectious diseases in 2003-2005", has been substantiated.     

Evolutionary determinants of genetic variation in susceptibility to infectious diseases in humans

Although genetic variation among humans in their susceptibility to infectious diseases has long been appreciated, little focus has been devoted to identifying patterns in levels of variation in susceptibility to different diseases. Levels of genetic variation in susceptibility associated with 40 human infectious diseases were assessed by a survey of studies on both pedigree-based quantitative variation, as well as studies on different classes of marker alleles. These estimates were correlated with pathogen traits, epidemiological characteristics, and effectiveness of the human immune response. The strongest predictors of levels of genetic variation in susceptibility were disease characteristics negatively associated with immune effectiveness. High levels of genetic variation were associated with diseases with long infectious periods and for which vaccine development attempts have been unsuccessful. These findings are consistent with predictions based on theoretical models incorporating fitness costs associated with the different types of resistance mechanisms. An appreciation of these observed patterns will be a valuable tool in directing future research given that genetic variation in disease susceptibility has large implications for vaccine development and epidemiology.     

Applying population-genetic models in theoretical evolutionary epidemiology

Much of the existing theory for the evolutionary biology of infectious diseases uses an invasion analysis approach. In this Ideas and Perspectives article, we suggest that techniques from theoretical population genetics can also be profitably used to study the evolutionary epidemiology of infectious diseases. We highlight four ways in which population-genetic models provide benefits beyond those provided by most invasion analyses: (i) they can make predictions about the rate of pathogen evolution; (ii) they explicitly draw out the mechanistic way in which the epidemiological dynamics feed into evolutionary change, and thereby provide new insights into pathogen evolution; (iii) they can make predictions about the evolutionary consequences of non-equilibrium epidemiological dynamics; (iv) they can readily incorporate the effects of multiple host dynamics, and thereby account for phenomena such as immunological history and/or host co-evolution.     

Why genetic selection to reduce the prevalence of infectious diseases is way more promising than currently believed

Genetic selection for improved disease resistance is an important part of strategies to combat infectious diseases in agriculture. Quantitative genetic analyses of binary disease status, however, indicate low heritability for most diseases, which restricts the rate of genetic reduction in disease prevalence. Moreover, the common liability threshold model suggests that eradication of an infectious disease via genetic selection is impossible because the observed-scale heritability goes to zero when the prevalence approaches zero. From infectious disease epidemiology, however, we know that eradication of infectious diseases is possible, both in theory and practice, because of positive feedback mechanisms leading to the phenomenon known as herd immunity. The common quantitative genetic models, however, ignore these feedback mechanisms. Here, we integrate quantitative genetic analysis of binary disease status with epidemiological models of transmission, aiming to identify the potential response to selection for reducing the prevalence of endemic infectious diseases. The results show that typical heritability values of binary disease status correspond to a very substantial genetic variation in disease susceptibility among individuals. Moreover, our results show that eradication of infectious diseases by genetic selection is possible in principle. These findings strongly disagree with predictions based on common quantitative genetic models, which ignore the positive feedback effects that occur when reducing the transmission of infectious diseases. Those feedback effects are a specific kind of Indirect Genetic Effects; they contribute substantially to the response to selection and the development of herd immunity (i.e., an effective reproduction ratio less than one).     

Prevalence and structure of acute respiratory virus infections

Information on epidemiology of acute respiratory virus infections (ARVI) is reviewed and analyzed. In addition to influenza viruses, the role of respiratory syncytial viruses (RSV), rhino- and adenoviruses, as well as other viruses, in the development of respiratory diseases, especially in newborns, young children and elderly persons, is emphasized. A high proportion of RSV in the etiology the severe forms of ARVI and in the development of intrauterine infection is pointed out. The conclusion has been made that the identification of the causative agents of ARVI with the use of modern methods makes it possible to determine the real role of each of the pathogens in the formation of the severe forms of diseases, as well as the expediency of vaccinal prophylaxis.     

Emergency situations in the Republic of Ingushetia and the prevention of their epidemiological consequences

Information on the sanitary and epidemiological situation and water supply in the Republic of Ingushetia during the period before and after the emergency situation (high flood) is presented. The results of epidemiological observations on the territory of the Republic of Ingushetia for the period of June 22 to the end of the year 2002 indicate that no considerable rise in infectious morbidity, as well as outbreaks of natural focal infections, was noted. This suggests that, in spite of the complicated sanitary and epidemiological situation before the emergency situation (due to the vicinity of the conflict in the Chechen Republic, the intensive migration of the population and the presence of a large of refugees on the territory of the Republic of Ingushetia) and its sharp deterioration caused by the high flood, the timely realization of a complex of sanitary and prophylactic measures made it possible to avoid the wide spread of infectious diseases.     

Real time bayesian estimation of the epidemic potential of emerging infectious diseases

Background

Fast changes in human demographics worldwide, coupled with increased mobility, and modified land uses make the threat of emerging infectious diseases increasingly important. Currently there is worldwide alert for H5N1 avian influenza becoming as transmissible in humans as seasonal influenza, and potentially causing a pandemic of unprecedented proportions. Here we show how epidemiological surveillance data for emerging infectious diseases can be interpreted in real time to assess changes in transmissibility with quantified uncertainty, and to perform running time predictions of new cases and guide logistics allocations.

Methodology/Principal Findings

We develop an extension of standard epidemiological models, appropriate for emerging infectious diseases, that describes the probabilistic progression of case numbers due to the concurrent effects of (incipient) human transmission and multiple introductions from a reservoir. The model is cast in terms of surveillance observables and immediately suggests a simple graphical estimation procedure for the effective reproductive number R (mean number of cases generated by an infectious individual) of standard epidemics. For emerging infectious diseases, which typically show large relative case number fluctuations over time, we develop a Bayesian scheme for real time estimation of the probability distribution of the effective reproduction number and show how to use such inferences to formulate significance tests on future epidemiological observations.

Conclusions/Significance

Violations of these significance tests define statistical anomalies that may signal changes in the epidemiology of emerging diseases and should trigger further field investigation. We apply the methodology to case data from World Health Organization reports to place bounds on the current transmissibility of H5N1 influenza in humans and establish a statistical basis for monitoring its evolution in real time.     

Role of various diseases of the upper respiratory tract in the epidemiological process of streptococcal infections]

Investigations conducted with the use of a specially elaborated method revealed a specific association of some (15--24%) of diseases diagnosed clinically as "acute respiratory affection" (ARA) with streptococcus infection. This was also confirmed by detection of an epidemiological association of ARA with scarlet fever revealed in some child collective bodies. The data obtained pointed to the definite role played by such diseases in the epidemic process in streptococcus infections.     

糖尿病流行病学研究策略及分子遗传学研究进展

流行病学是现代医学的一门重要的基础学科,也是一门应用广泛的应用学科。流行病学作为方法学在复杂疾病研究中有不可替代的作用。糖尿病具有复杂疾病属性,应该以系统的多层次的流行病学方法为研究策略。本文从流行病学与临床医学、遗传学及分子生物学交叉所形成的分支学科一临床流行病学、遗传流行病学及分子流行病学三个方面对糖尿病的研究进展作一综述,并从分子遗传学角度列举了部分糖尿病的候选基因。提出糖尿病的研究应该从宏观流行病学（如社会环境等因素的影响）和微观流行病学（如分子遗传等）结合系统地进行研究。