1. Epidemiology. Doctrine about epidemiological process
Epidemiology. Doctrine about epidemiological process. Classification of infectious diseases

2. There are as many numbers of definitions as there are books on epidemiology.
E. is the study etiology and spreading of infectious diseases in a human community and is aimed at prevention, control, and final eradication of these diseases (Prague, 1960).
“Study of the occurrence of illness” (Gaylord Anderson, 1979) .

3. Considering the wide range of areas in epidemiologic research and the major methodologies involved a comprehensive definition would be –
Epidemiology is the study of frequency, distribution and determinants of health related events.
This is a synthesis of the major ideas given by expert epidemiologists.

4. Frequency – implies measurements summarized information
Frequency – implies measurements summarized information. It is essential for comparing information and different problems or magnitude of same problem among different groups. Study of frequencies makes epidemiology a quantitative science. It may be expressed as rates or proportions. They are simple arithmetic expresions.

5. Distribution implies the study of the patterns of the health problem in a community. For example, which age group or gender group is more affected or which geographic area is affected or spared and what is the time of the year when problems are more or less, etc.

6. Determinants mean causative factors.
Information on both frequency and distribution throws light on possible causative factors.
The analytical approach in epidemiology tests the hypothesis thus made, and arrives at definite conclusions on causative factors. Biostatistics is the tool for making these measurements.

7. E. is a very old word dating back to 3 rd century BC
E. is a very old word dating back to 3 rd century BC. It is derived from three words in Greek: Epi = Upon + Demos = People + Logos = Study of.
E. developed into a science of separate identity during 20th century. There are references about epidemiological studies conducted many years before. Many of the epidemiologists in these formative years were physicians who were challenged by the health problems.

8. D. Samoilovich ( )

9. E. Jenner ( )

10. L. Pasture ( )

11. D. K. Zabolotny ( )

12. M. F. Hamalia ( )

13. E. N. Pavlovsky ( )

14. L. V. Gromashevsky ( )

15. AIM OF EPIDEMIOLOGY
The International Epidemiological Association (IEA) has listed three main aims for the science of e.
To describe the distribution and magnitude of health and disease problem in human population.
To identify etiological factors (risk factors) in the pathogenesis of disease.
To provide the data essential to the planning, implementation and evaluation of services for the prevention, control and treatment of disease and to setting up of prioritiesamong those services.

16. Microorganisms causing i. d
Microorganisms causing i.d. parasitize on host and persist due to continuous reproduction of new generations. Then the pathogenic microorganism can survive by changing its residence, via a corresponding transmission mechanism. This continuous chain of successive transmission of infection (patient-carrier), manifested by symptomatic or asymptomatic forms of disease, is called an
epidemic process

17. Epidemiological process – circulation of infectious diseases among people
Epizootological process – circulation of infectious diseases among animals.

18. Source of infectious agents is an object of natural habitation and multiplication of the pathogenic microorganisms and in which they may accumulated. Since pathogenic microorganisms are parasites, only living macroorganism can be such an object, a human or an animal

19. Source of infectious agents
Human – patient or carrier (from the end of the incubation period; prodromal period; climax period; convalescence, when microorganism excretion occur) - antroponosis
Animals (domestic, wild) – zoonosis
Antropozoonosis (both man and animal can be the source)
Environment – sapronosis (tetanus, legionellosis)

20. Epidemic focus is the residence of infection source including the surrounding territory within the boundaries of which, the source can, under given conditions, transmit a given disease through the agency of the pathogenic microorganisms.

21. The focus of infection remains active until the pathogenic microorganisms are completely eradicated, plus the maximal incubation period in persons that were in contact with the source of infection.

22. The combination of routes by which the pathogenic microorganisms are transmitted from an infected macroorganism to a healthy one is called the mechanism of infection transmission.

23. Fecal-oral (intestinal localization); Air-borne (respiratory tract);
4 mechanisms of transmission are distinguished according to the primary localization of pathogenic agents in macroorganisms:
Fecal-oral (intestinal localization);
Air-borne (respiratory tract);
Transmissive (blood circulating system);
Contact (wound) (biological fluids)

24. Excretion from an infected macroorganism;
3 phases are distinguished in the transmission of infection from one person to another:
Excretion from an infected macroorganism;
Presence in the environment;
Penetration into a healthy macroorganism.

26. The method by which agents are excreted from an infected macroorganism depends on the localization of pathological process.
The presence of causative agents outside of macroorganism (2-nd phase) is connected with various environmental objects.
The environmental objects that transmit the pathogenic agents from one person to another are called transmission factors.

27. Fecal-oral mechanism

28. Air-borne mechanism

29. Transmissive mechanism

30. Contact (wound) mechanism

31. Susceptibility is a biological property of organism, characterized by optimum conditions for multiplication of pathogenic microorganisms. S. is a species property that is transmitted by hereditary trait.
Immunity
Hereditary Acquired
(species) Natural Artificial
(active, passive)

32. Natural active i. is formed as a result of a sustained disease (postinfection or acquired).
Natural passive – from the mother to child (intrauterine). Newborn acquires it with mothers milk.

33. Artificial active immunity (postvaccinal)
develops during 3-4 weeks and persists from 6 months to 5 years.
Artificial passive immunity is created by administration of antibodies (serum, immune globulin). It persists for 3-4 weeks.

34. Sterile immunity microorganism is disappear from the macroorganism after the treatment.
Non-sterile immunity immunity persists until the pathogenic agent remains in the macroorganism globulin).

35. Community immunity is non-susceptibility of a community to a given infection. Created by specific prophylactic and other measures that are taken by health-care services, and also by improvement of well-being of population.

36. Main motive forces of epidemiological process:
Source of infectious agent
Mechanisms of infectious agent transfer
Receptive organism
Secondary motive forces
of epidemiological process:
Social factors
Environmental factors

37. PRINCIPLES OF EPIDEMIOLOGY
I principle
Source of infectious agent is infected (sick or carrier) organism - human or animal
(object which is the site of natural habitation and multiplication of pathogenic organisms, from where they can infect healthy people)

38. PRINCIPLES OF EPIDEMIOLOGY
II principle
Infectious agent’s localization in the organism and mechanism of it’s transmission from one individual to another form persistent connection, which provide pathogenic species preservation in the environment and continuity of epidemic process of infectious disease.

39. Mechanism of infectious agent’s transmission
1st phase: excretion of the causative agent from the infected macroorganism
2nd phase: staining of the causative agent in environment
3rd phase: infectious agent’s penetration into healthy (susceptible) organism

40. PRINCIPLES OF EPIDEMIOLOGY
III principle
Infectious diseases can be rationally classified according to specific localization of infectious agent in the organism, corresponding mechanism of transmission and main biological properties of causative agent:
intestinal infections
respiratory infections
blood infections
infections of external covers

41. PRINCIPLES OF EPIDEMIOLOGY
IV principle
Epidemic process originates and maintained only due to combined action of three main motive forces:
Presence of infectious agent’s source;
Realization of transmission mechanism;
Population susceptibility to the infection.
If any of these factors is excluded, epidemic process stop

42. PRINCIPLES OF EPIDEMIOLOGY
V principle
Natural and social factors stipulate quantitative and qualitative changes in the epidemic process (increase or decrease), thus they are
secondary motive forces
of epidemic process

43. EPIDEMICAL FOCUS
site of infectious agent habituation, including surrounding territory with the limits where it can be contagious for others.
Epidemical focus exist in time (maximal incubation period of the disease) and in area (determined by transmission mechanism)

44. ANTIEPIDEMIC MEASURES IN THE FOCUS OF INFECTION
Measures concerning infectious agent’s source
Disease diagnosis
Registration
Isolation of the patient (carrier)
Etiological treatment
Measures concerning transmission mechanisms
disinfection (disinsection, deratization) – current, final
Measures concerning contact persons:
Sanitary processing
Medical observation
Laboratory examination
Specific prophylaxis

45. DEGREES OF INFECTION’S SPREADING:
Sporadic – normal level of morbidity for the given territory in a given period of time
Epidemic – morbidity in a few times more higher than sporadic
Pandemic – extraordinary intensive epidemic process and considerably greater than epidemic.
Endemic infections – connected to certain territory.
Exotic infections – diseases, which are not characteristic for the local territory, but can be transferred from other countries.

46. Localization of infectious agent in organism
PRINCIPLES OF INFECTIOUS DISEASES CLASSIFICATION (ACCORDING TO L. GROMASHEVSKY)
Localization of infectious agent in organism
Mechanisms responsive for transmission of infectious agent

47. GROUPS OF INFECTIOUS DISEASES (according to Gromashevsky)
Intestinal infections – are transferred by fecal-oral mechanism
Respiratory infections – are transferred by the droplet mechanism
Blood infections – by means of transmissive mechanism of transfer
Infections of external covers – by means of contact or contact-wound mechanism
Distinguished trans-placental (vertical) mechanism of transfer, and accordingly, infections which are transferred by trans-placental way

48. THE TOOLS OF EPIDEMIOLOGY
Clinical medicine, immunology, microbiology, pathology, demography, and statistics. The use of each of these tools for achieving a specific objective forms for tpidemiologic method.

49. Epidemiological methods
For achieving the above objectives various methods are used by epidemiologists. They have evolved from 19th century:
1. Observational
2. Experimental
Observational – as the name implies involves only making observations on what has happened to persons and communities and make inferences from these observations.
It may be further classified into descriptive and analytical.

50. Descriptive studies
observe health phenomena in terms of time / place / person.
Cross-sectional made on populations or communities at one point of time. They give information on the community just as a cross section of a specimen gives informationat that particular level of sectioning.
Longitudinal surveys conducted over long periods in the same population. They give information over different time points. Useful in calculating incidence rates and drawing time trends in health and disease.

51. Analytical designs
Based on specific hypothesis generated from cross sectional or longitudinal studies. Used to gather data and the data is analysed to test the specific hypotesis. May be called retrospective studies when both the exposure and outcome has occurred before the study commences. They are prospective when both exposure and outcomes are yet to occur.

52. Experimental design
Are methods where suspected causal situation is induced in selected and control populations and their effects are observed to prove or disprove a hypothesis. The major modalities of experimental designs in vogue currently may be classified as follows:
Randomised controlled clinical trial;
Field trials;
Community trials.

53. Inspection – revealing of the source
Examination – studying of morbidity
Analysis of morbidity
Experiment – microbiological and serological examination, physical and chemical studies, experiment on humans and animals

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