Эпидемиология = Epidemiology

 Л. П. Мамчиц



            Эпидемиология


            Epidemiology


  Допущено
  Министерством образования Республики Беларусь в качестве учебного пособия
  для иностранных студентов учреждений высшего образования по специальности «Лечебное дело»













       Минск «Вышэйшая школа» 2021

УДК 616-036.22(075.8)-054.6
ББК 51.9я73
    М22




    Рецензенты: кафедра эпидемиологии УО «Белорусский государственный медицинский университет» (доцент кафедры кандидат медицинских наук О.А. Горбич); доцент кафедры инфекционных болезней УО «Гродненский государственный медицинский университет» кандидат медицинских наук, доцент Ю.В. Кравчук



















      Мамчиц, Л. П.
М22 Эпидемиология = Epidemiology : учебное пособие / Л. П. Мамчиц. - Минск : Вышэйшая школа, 2021. - 191 с. : ил.
          ISBN 978-985-06-3373-6.

          В учебном пособии представлен основной программный материал по общей эпидемиологии. На современном уровне освещены теоретические основы эпидемиологии и принципы организации противоэпидемической работы, а также система организации эпидемиологического надзора. Приведены практические задачи и тестовые задания для студентов по изучаемой дисциплине.
          Предназначено для проведения практических занятий по эпидемиологии со студентами факультета иностранных студентов в медицинских учреждениях высшего образования Республики Беларусь.

УДК 616-036.22(075.8)-054.6
ББК 51.9я73

ISBN 978-985-06-3373-6                         © Мамчиц Л.П., 2021
© Оформление. УП «Издательство
“Вышэйшая школа”», 2021

FOREWORD


   Teaching epidemiology in the system of higher medical education aims to form students’ preventive thinking and acquire scientific knowledge about the patterns and features of the epidemic process of infectious diseases that are relevant for the population of the Republic of Belarus. It is also aimed at mastering practical skills and abilities of preventive and anti-epidemic measures by students.
   Further advancement of student training requires improving the arrangement, concretising the content and practical orienting of the self-study of learners while studying the discipline.
   The proposed textbook on general epidemiology is the result of generalising the experience of teaching this academic discipline at Gomel State Medical University. The textbook covers all units, and its chapters corresponding to the topics of the curriculum that was made in accordance with the requirements of the current State Educational Standard of higher professional education in medical specialities.
   Situational tasks, algorithms for self-study, assessment tests to check course content mastering and practical recommendations for conducting preventive and anti-epidemic measures take a significant place in the textbook. This allows one to guide, organise and control the individual cognitive activity of students while studying the discipline.
   The textbook is made in accordance with the standard curriculum in epidemiology for the medical faculty. It can be used to have classes for students of the medical and medical diagnostic faculties.
   The author will gratefully accept all comments and suggestions aimed at improving the textbook.

LIST OF KEY TERMS AND CONCEPTS
USED IN EPIDEMIOLOGY

   Analytical (Gr. “analysis” - decomposition, dissection) epidemiological methods - methods designed to establish the causes of the occurrence and spread of diseases, i.e. risk factors. Analytical population studies include the establishment of statistical relationships (correlation analysis) and comparative studies. Currently, the latter include “case-control” and cohort studies.
   A biological species - an aggregate of natural populations united by a single gene pool.
   A natural factor in epidemiology - a combination of abiotic and biotic elements of the external environment, which directly or indirectly (through changes in social conditions) have an activating or inhibiting effect on the epidemic process.
   An uncontrolled epidemiological experiment - an epidemiological study based on the results of the intervention in the development of the epidemic process by carrying out anti-epidemic measures while providing for the allocation of control groups. To evaluate the results, equivalent teams or periods of time are selected that differ in their application (non-application) or the quality of the events.
   Anti-epidemic measures - a set of scientifically grounded and justified by practical activities measures to combat emerging infectious diseases among people.
   Anthroponoses (Gr. “anthropos” - human + “nosos” - disease) are infectious diseases in which humans are the reservoir of the causative agent.
   Anthropurgical (Gr. “anthropos” - human + “ergon” - activity, action) focus of infection - a focus of zoonotic infection formed in connection with human activities.
   A randomised controlled trial (RCT) - an epidemiological trial that is usually organised as a cohort study with a randomised sample.
   A reservoir (Lat. “reservare” - to preserve, conserve) of an infectious agent is a set of conditions that make up the natural habitat of the pathogen and ensure the maintenance of its populations. The reservoir of the causative agents of anthroponosis is the human organism, of zoonoses - the organism of animals, the reservoir of sapronoses is the external environment.
   A social factor in epidemiology - a set of social connections and relationships that have an activating or inhibiting effect on the epidemic process.
   Biocenosis (Gr. “bios” - life + “koinos” - common) - the cumulative, evolutionarily formed existence of different species of living beings in the same environment.
   Cohort analytical epidemiological study - a study based on the comparison of the incidence in equal groups (cohorts) exposed and not exposed to a hypothetical risk factor.
   Contagiosity (Lat. “contagiosus” - contagious) - 1) contagiousness; 2) a species property of a pathogen characterised by the probability of movement (transmission) from one host individual to another (others).


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    Controlled infections - infectious diseases for which scientifically based measures have been developed and their effectiveness has been shown. There are groups of infections controlled by 1) means of immunoprophylaxis, 2) sanitary and hygienic measures, and 3) other types of measures.
    Dynamics (Gr. “dynamikos” - having force) of the epidemic process - the change in the incidence of infectious diseases in people over the years (cyclicity), months during the year (seasonality) and shorter intervals during a single epidemic. It is determined by social, biological and natural factors.
    Elimination (Fr. “Elimination” - destruction) of infection - the eradication of the nosological form of an infectious disease due to the destruction (eradication) of the pathogen as a bioloEgical species on a global scale. Global elimination goes through the stages of its regional elimination, achieved by the destruction of the pathogen within the administrative territories and the creation in these territories of conditions that prevent the rooting of the pathogen in the event of importation.
    Epidemiological diagnosis - causes (risk factors) of the occurrence and spread of pathological conditions.
    Epidemic tendency - the main directions of changes in the intensity of the epidemic process in long-term dynamics. Reflects the stabilisation, increase or decrease in the incidence.
    Epidemic year - an interval that includes the first month of a seasonal increase in incidence in one calendar year and the month preceding a new seasonal increase in incidence in the next calendar year.
    Epidemiological surveillance - a continuous assessment of the state and development trends of the epidemic process in order to determine the reasons for its development and timely decision-making, ensuring that measures are taken adequate to the situation.
    Evidence-based medicine - a branch of medicine based on epidemiological diagnostic methods that involves the search, comparison, synthesis and wide dissemination of the evidence obtained regarding the effectiveness of means and methods of the disease prevention and treatment.
    Experimental epidemiological methods - methods used to show epidemiological hypotheses and assess the effectiveness of anti-epidemic measures. Based on artificial intervention in the natural development of the epidemic process.
    Immunity (Lat. “immunitas” - liberation from something) - a specific immunity to infectious agents and their toxins, produced by the interaction of the body with the antigen.
    Immunogenicity (“immune” + Gr. “genes” - born) - a specific property of a parasitic pathogen that manifests itself in the ability to cause certain forms of immunity in the host organism.
    Immunological structure of the population - the distribution of people in the population by the presence or absence of immunity, and the immune stratum - by the strength of immunity.
    Invasion - 1) infection with protozoa and helminths; 2) the process of interaction between the host organism and a parasite belonging to protozoa or helminths. Can manifest in a manifest form of varying degrees of severity or develop asymptomatically.

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    Infectious diseases - diseases that develop as a result of the introduction, reproduction and vital activity of viruses and prokaryotes in the body of patients. The nosological form of the disease is determined by the species specificity of the pathogen.
    Infectious Disease Control (ID) - a system of continuous epidemiological surveillance in a health-care facility with epidemiological analysis of the results of this surveillance and targeted measures based on epidemiological diagnosis to improve the quality of medical care.
    Infectious process - a process of interaction between a parasitic pathogen and a host (human, animal), manifested by a disease or illness.
    Infection (Lat. “infectio” - infection) - 1) infectious process; 2) nosological form of infectious disease; 3) a specific infectious disease.
    Health care-associated infections, or “nosocomial” and “hospital” infections -infections that affect patients in a hospital or other health-care facility, and are not present or incubating at the time of admission. They also include infections acquired by patients in the hospital or facility but appearing after discharge, and occupational infections among staff.
    Heterogeneity (Gr. “heterogenes” - heterogeneous, of different origin) of a population is the heterogeneity of the individuals that make up the population. Phenotypic heterogeneity is genetically determined.
    Homogeneity (Gr. “homogenes” - homogeneous, of the same origin) of a population - the relative homogeneity of individuals (clones) according to the analysed trait.
    Localisation (lat. “localisatio” - location) of a pathogen in a specific host - the location of the pathogen in an infected organism, determined by the pathogen’s tropism, which determines the mechanism of transmission. Four types of main localisation are typical of anthroponotic pathogens: on the mucous membranes of the respiratory tract, in the intestines, on the skin and external mucous membranes, and in the blood. Possible, along with the main localisation, is secondary (a pathogenetic pattern during the development of an infectious or invasive process, or its complication, in particular penetration into the fetus).
    Manifestation of infection - the proportion of infected people with manifestations of the disease characteristic of certain nosological forms of infectious diseases. It is determined by the specific characteristic of the pathogenicity of the pathogen, the specific degree of its virulence, the structure of the human population according to the degree of susceptibility, as well as the likelihood during the development of the epidemic process of infection with doses of the pathogen leading to manifestation.
    Meta-analysis (synthesis of information) - a review that summarises data from several population studies using a quantitative method of assessment (mainly randomised controlled trials) devoted to one problem, and the final result is presented as one summary indicator.
    Mortality - an index that reflects the number of deaths among patients with any nosoform, expressed as a percentage.
    Mortality rate - an index that reflects the number of deaths from any nosoform in the population, most often expressed as a rate per 100,000 population.

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    Natural focus - 1) a part of the territory of the geographical landscape, within which, among wild animals, the pathogen is transmitted from the donor to the recipient; 2) a population of the pathogen formed independently of human activity, together with populations of vertebrate hosts that support it (with transmissible infections and populations of arthropods, with sapronosis and specific environmental conditions).
    Operational epidemiological analysis - a dynamic assessment of the state and development trends of the epidemic process, designed to identify not sustainable trends, but emerging outbreaks (epidemics). It is carried out with the help of constant analysis of the registration of emerging diseases (assessment of the dynamics in time, space, in different population groups) and the establishment of statistical links with a factor that could cause an outbreak (epidemic). It includes epidemiological examination of foci, various laboratory diagnostic methods. Operational analysis is an integral part of epidemiological surveillance.
    Parasitic agents - 1) eukaryotes (fungi, protozoa, helminths and arthropods) that have a pathogenic effect on the organism; 2) parasites of all systematic groups capable of causing disease.
    Pathogenicity (Gr. “pathos” - suffering, disease + “genes” - born) - a specific property of a parasitic pathogen, characterised by its ability to cause disturbances in the host’s normal physiological processes, i.e., illness. It is provided with the mechanisms of adhesion, invasion, reproduction and distribution, as well as the production of specific functional active substances (pathogenicity factors), including toxins.
    Population (Lat. “populatio”) - an aggregate of individuals of a biological species, relatively isolated in its natural life from other aggregates of individuals of this species.
    Population immunity - a specific protection against any parasite of the population or its individual groups. It is determined by the specific gravity of immune people.
    Preventive measures - a set of scientifically grounded and justified by practical activities, designed to prevent the emergence and spread of any pathological conditions among people.
    Pro-epidemic - the formation of a high level of population immunity as a result of active circulation of the pathogen due to asymptomatic forms of infections or lungs, undiagnosed diseases.
    Randomisation - a way to control interfering factors by randomly distributing the studied persons or phenomena into groups.
    Resistance (Lat. “resistentia” - resistance, elasticity) - the immunity of individuals to a disease, not depending on the specific factors of immunity. Determined by genotype and phenotypic factors.
    Retrospective epidemiological analysis - is carried out in order to establish the main trends in the nature and causes of the development of the epidemic process. The analysis is carried out using statistical methods for researching hypotheses about risk factors. The final stage of the retrospective analysis is the epidemiological conclusion about the causes and conditions that determine the incidence rate in the

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territory. The results of the analysis are used to develop plans for complex organisational, sanitary and anti-epidemic measures.
    Sapronoses - infectious diseases, the reservoir of pathogens of which is the external environment.
    Source of infection (source of the infectious agent) - 1) the natural environment of the parasitic pathogen; 2) the infected human or animal organism from which the patient became infected (in facultative parasitism - objects of the environment).
    Spatial characteristic - the distribution of frequency indicators (intensity) over the territory.
    Specific prophylaxis - the artificial creation of immunity in individuals or population immunity.
    Susceptibility - a species-specific property of a specific host to respond with an infectious process to the introduction of an infectious agent. The degree of susceptibility is determined by non-specific protective factors and immunity.
    Systematic reviews - a literature review that critically assesses and summarises the results of primary research on a specific issue.
    The biological factor in epidemiology - the evolutionary nature of the population relations of biological species, parasite and host. The biological factor reflects the specificity of the epidemic process.
    The time of risk - the period of increased morbidity rates.
    Virulence (Lat. “virulentus” - poisonous) - a measure (degree) of pathogenicity of a pathogen.
    Ways of transmission of the pathogen - specific elements of the external environment or their combinations, which ensure the transfer of the pathogen from one organism to another under specific conditions of an epidemic situation.
    Zoonoses (Gr. “zoon” - animal + “nosos” - disease) - infectious diseases whose pathogen reservoirs are animals (“diseases from animals”). The human body is more often a biological dead end.

LIST OF ABBREVIATIONS


AEFI - adverse events following immunisation
AIDS - acquired immunodeficiency syndrome
ALAT - alanine aminotransferase
ASAT - aspartate aminotransferase
BA - biological agents
BCG - Bacillus Calmette-Gurin
BDO - biological defence organisations
BM - biological means
BW - biological weapons
CCM - cold chain monitor card
GBS - Guillian-Barre syndrome
DOT- direct observed therapy
DT - diphtheria and tetanus toxoids
DTaP - diphtheria and tetanus toxoids and acellular pertussis
DTP - diphtheria toxoid, tetanus toxoid, and pertussis
ELISA - enzyme-linked immunosorbent assay
HepB - hepatitis B
HEV - hepatitis E virus
Hib - haemophilus influenzae type b
HIV - human immunodeficiency virus
HDCV - inactivated, human diploid cell rabies vaccine
HIV - human immunodeficiency virus
IgM - immunoglobulin M
IgG - immunoglobulin G
ID - intradermal
IBD - immunobiological drugs
IB - immune blotting
IIV - inactivated influenza vaccine
IPV - inactivated poliovirus
LAIV - live, attenuated influenza vaccine
MMR - measles, mumps, and rubella
MMRV - measles, mumps, rubella and varicella
OPV - oral polio (myelitis) vaccine
PAT - portable appliance testing
PCV13 - pneumococcal conjugate vaccine
PPSV23 - pneumococcal polysaccharide vaccine

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      PRP - polyribosylribitol phosphate
      PCECV - inactivated, purified chick embryo cell rabies vaccine
      PVH - parenteral viral hepatitis
      RIG - rabies immunoglobulin
      RV- rotavirus vaccines
      RT-PCR - reverse transcriptase polymerase chain reaction
      SCID - severe combined immune deficiency
      STD’s - sexually transmitted diseases
      Td - tetanus and diphtheria toxoids
      Tdap - tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis
      TIG - tetanus immune globulin
      TTA - tetanus toxoid adsorbed
      TT - tetanus toxoid
      TB - tuberculosis
      WHO - World Health Organisation