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EPIDEMIOLOGY PRACTICALS

EPIDEMIOLOGY PRACTICALS. 2014 - 2015. PRACTICALS - SUBJECTS I. Epidemiological inquiry for transmissible diseases II. Elements of Immunoepidemiology . Vaccines available under the National Immunisation Program III. Vaccines used in special epidemiological situations

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EPIDEMIOLOGY PRACTICALS

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  1. EPIDEMIOLOGYPRACTICALS 2014 - 2015

  2. PRACTICALS - SUBJECTS I. Epidemiological inquiry for transmissible diseases II. Elements of Immunoepidemiology. Vaccines available under the National Immunisation Program III. Vaccines used in special epidemiological situations IV. Serum-prevention, Immunoglobulin-prevention Immunomodulators V. Decontamination and sterilization VI. Laboratory investigations in practical epidemiology VII. Epidemiological surveillance of transmissible diseases

  3. EPIDEMIOLOGICAL PROCESS (EP) - All the factors, phenomena and biological, natural and social mechanisms, which participate, in a determining or favouring way, to the occurrence, extension and particular evolution of a disease in a population.

  4. “If you have an apple and I have an apple and we exchange these apples then you and I will still each have one apple. But if you have an idea and I have an idea and we exchange these ideas, then each of us will have two ideas.” George Bernard Shaw

  5. A. DETERMINING FACTORS I. SOURCE OF PATHOGENIC AGENTS • humans sick persons – with typical disease - withatypical disease (subclinical, asymptomatic) carriers of pathogenic agents: - pre-infectious = “before infection “ carrier (influenza, measles, HBV) - healthy carrier - post-infectious = “after infection”carrier (people in their recovering period / chronic) • animals (including birds) ill / carrier • biologic active vectors ( , , )

  6. A. DETERMINING FACTORS II. MODES AND WAYS OF TRANSMISSION direct mode -agents with low environment resistance - Pflügge drops - blood transfusion - transplacental - unprotected sexual contact - direct contact with skin lesions indirect mode - agents with strong environment resistance - through contaminated routes of transmission: → air, water, soil, → food, objects, hands, → biologic passive vectors

  7. A. DETERMINING FACTORS III. RECEPTIVE HOST → receptivity status in relation to: • non-specific general resistance (mucosal barriers, cough or sneeze reflex) 2. specific resistance (immunity) • natural - species immunity - active acquired - passive acquired • artificial - active acquired - passive acquired just a part of animals’ diseases can be transmitted to human → as a result of a disease Ag → transplacental + breastfeeding Ab → vaccination →Ig, immune serum

  8. B. FAVOURING FACTORS • → bring together the three determining factors • → modulate the manifestation forms of epidemiological process • I. Natural factors: • Cosmic • - radiations, sun activity • Meteorologic • - temperature, atmospheric pressure, air currents • Climatic • - latitude and altitude • Geographic • - landforms

  9. B. FAVOURING FACTORS II. Socio-economic factors: 1.living and working conditions: - income - level of education - home - diet - healthcare 2. occupational conditions: - qualification - seniority - work area - agents of aggression

  10. PRACTICAL IEpidemiological inquiry (epidemiological investigation) in transmissible diseases

  11. EPIDEMIOLOGICAL INQUIRY/ INVESTIGATION (E.I.) all the investigations performed in different groups of people in order to identify causes of transmissible or non-transmissible diseases and their evolution to elaborate the measures of their prevention and control

  12. OBJECTIVES ? 1. to solve epidemiological emergencies 2. to know the risk factors involved in the occurrence of some non-transmissible diseases (NTD) Ex.H. pylori → peptic ulcer Chlamydia → atheromatous disease 3. to identify the multifactorial aetiology of NTD with a large distribution among population Ex. tobacco, HTA, dyslipidemia, obesity, stress – for CVD 4. to make predictions about natural history of transmissible diseases (TD)

  13. 5. to avoid the “import” and the “export” of some TD Ex. “import” for Romania → malaria brought from Turkey - “export” for Romania → TB for persons from areas where the disease is under control (West European countries) – when they travel to Romania 6. orientation of biological materials production 7. improving national and international programs of prevention and control 8. to evaluate the effectiveness of prevention and control measures applied in population OBJECTIVES

  14. METHODS FOR ACHIEVING THE E.I. • patienthistory→from him and/or from his family 2.epidemiological observation →identification of a phenomenon in the population 3.descriptive method →detailed representation of a phenomenon 4.analytical method →identification and studying the components of a health problem in order to achieve its characterization within the population that emerged and the factors that have competed at the onset morbid phenomenon 5. analytical method + biostatistics→meta-analysis=systematic procedure of combining the results of different studies on the same topic

  15. METHODS FOR ACHIEVING THE E.I. 5.the epidemiological experiment→verification of hypothesis regarding the occurrence and evolution of an epidemiological process 6.comparison (historical, geographical, between population – by age, sex, profession)→knowledge of the natural history of a disease, temporal and spatial features of the EP and clinical symptoms 7.the screening→identification of probably affected individuals detected in a population of apparently healthy in order to be subject to further investigation or to implement early preventionmeasures 8.biostatistics →can be associated with any of the methods listed above, to increaseefficiency in synthesizing and interpreting information obtained 9.mathematical method→ involvestransposition of biological, medical and social parameters into mathematical equations, using epidemiological and mathematical models

  16. Types of epidemiological inquiry A. Operational epidemiological inquiries for prevention for control (emergency) B. Special epidemiological inquiries (for research) 1. descriptive (transversal observational / cross-sectional)– development of hypothesis - case raport - case series - ecological studies / correlational studies - prevalence studies 2. analytical – demonstration of hypothesis a) etiological observational: -case-control study - cohort study b) interventional – clinical trial 3. meta-analysis – verifying of hypothesis 4. decision analysis studies– application in practice

  17. A. Operational Epidemiological Inquiry

  18. Epidemiological inquiry for prevention • assess population health and the risks to which it is exposed • health status → indicators: - average lifespan (F=75,8 years; M=68,7 years) • may be single or repeated ~ for the same person, to the entire population or only to a sample • Cross-sectional EI • Longitudinal type of EI

  19. II. Epidemiological inquiry for control (emergency) • to stop the evolution of the epidemiological process and to eradicate its development • practical utility in transmissible diseases • performed by family doctor (general practitioner) from urban or rural areas • is addressed to all categories of persons from the outbreak: - sick individuals -with typical or atypical forms of disease - suspects(persons alleged to present atypical or unapparent disease) - known carriersof pathogenic agents - former patientswhich are in the convalescent stage and for whom the diagnosis was determined retrospectively - direct and indirectcontactswith “index” case or cases

  20. Stages of Epidemiological Inquiry

  21. The stage of orientation (preliminary stage) →performed by the family doctor - early detection and diagnosisof disease cases - establishingthe maincharacteristicsfor the factors ofthe epidemiological process - development and implementation ofemergency anti-epidemic measures → isolation of patients, suspects and possible contacts - decontamination, disinsection, deratization - reinforcement ofhealth education measuresof the population - operative information transmittedto superior health units about the epidemiological situation and preliminary measures adopted (notification) - epidemiological inquiry sheet (reporting sheet)

  22. b) The studying stage(final stage) → family doctor + epidemiologist + other specialities → the final epidemiological inquiry is performed and the epidemiological inquiry sheet is completed • isolation modeand treatment of patients throughout the disease • final diagnosis of the diseaseand of the evolutionary form • epidemiological situation of the patient clinically cured and discharged → carrier • follow up - after returning at home • modes and routes of transmission of pathogenic agents and the effectiveness of their neutralization→DDD methods • epidemiological and clinical surveillance of contacts → maximum of the incubation period of the disease • evaluation of the population receptivity(immune background) • evaluation of preventive measuresused in the outbreak andaround its • health education measures

  23. E.I. Methodology Knowledge of the E.P. factors using the collection, analysing and interpretation of epidemiologicalinformation II. Elaboration of measures to eradicate the epidemiological process and to prevent its recurrence

  24. E.I. Methodology III. Checking the correct application of hygienico-sanitary and anti-epidemic measures and monitoring their effectiveness IV. Elaboration of the E.I. sheet

  25. I. Knowledge of the E.P. factors using the collection, analysing and interpretation of epidemiologicalinformation

  26. 1. Collection of the data → is achieved by: conversation (anamnesis or interview) epidemiological observation laboratory investigations special information

  27. The conversation (anamnesis, interview) → obtaining information about epidemiological factors ~ from sick people and / or their family • probable date and circumstances of contamination • date of real onset of illness → to determine the incubation period of the disease (retrospective) • to specify the infectious moment • identification of a single infectious moment • sometimes – many probable infectious moments • possible association between first symptoms and consumption of food, water

  28. The conversation (anamnesis, interview) • relationships with certain people in the family, relatives, community, workplace, public transport → among contacts we can find the source of pathogenic agents → receptive contacts - preventative measures (ATB, Ig) - travels - infectious pathologic history and what immune measures are taken → information about receptivity - patient environment → domestic animals, wild rodents, birds, arthropods → and established relationships with them, continuously or accidentally →information about the sources and about the routes of transmission

  29. Epidemiological observation • assessing the hygienico-sanitary conditions of the house • personal hygiene and food quality • how the residues are removed • the situation of plumbing installations • animal maintenance → in the outbreaks/ at work place / in the collectivity (community)

  30. Laboratory investigations • useful for: • sources of pathogenic agents detection • knowledge of population receptivity • knowledge of the modes and routes of transmission

  31. Special information • topographical situation of the village • type of soil and water sources • communications network • climate and weather conditions • morbidity, mortality • the situation of TD and vaccinations • food, drinking water

  32. 2. Analysis of epidemiological data systematization of information including in various documents (EIS, tables, graphs, drafts, maps etc.) facilitate the application of prevention and control measures

  33. 3. Data interpretation Analysing data from the diagnosed people table: - repeating the same name → existence of a family outbreak - repeating the same address → possible existence of a source in that home or community - repetition of the same age group→ the receptivity to the disease - mentioning the same profession→ the professional character of the disease Analysing the drawings (maps) of the village or community where the epidemiological outbreaks occurred →possible clustering of disease in the area near the source of drinking water → information regarding the source of pathogenic agent, the modes and routes of transmission Data presented in the graphs → conclusions regarding the onset, the evolution mode, the peak of the epidemiological event, the decreasing period etc.

  34. II. Elaboration of measures to eradicate the epidemiological process and to prevent its recurrence

  35. 1. Hygienico-sanitary measures (general) • Recommended by the law and specific regulation - Their objective is to improve the individual, family or community hygiene conditions, and of the natural or occupational environment

  36. 2. Anti-epidemic measures (for control) a) Measures for ill persons • Active early detection • Isolation in the hospital or at home • Nominal or numeric reporting • Decontamination and deratization Example: the VHB ill person b) Measures for suspects - The same as in the case of the ill people until the diagnosis is clarified.

  37. 2. Anti-epidemic measures (for control) c) Measures for contacts • isolation in family or community, quarantine • surveillance for the maximum duration of the incubation period of the disease • clinical examination, temperature • laboratory examination • chemical/antibiotic/serum/immunoglobulin/vaccine - prevention • D.D.D. measures • health education Example – contact with confirmed case of meningococcal meningitis

  38. 2. Anti-epidemic measures (for control) d) Measures for carriers • registration and follow up • microbiological “sterilisation” • surveillance • health education • exclusion from population risk sectors Example – healthy carrier of type A beta-haemolytic Streptococcus

  39. 2. Anti-epidemic measures (for control) e) Measures for convalescents - follow up (surveillance) Example - convalescent after type B viral hepatitis 1. Clinical and laboratory surveillance for 1 year: -at 1 month, at 3 months, at 6 months: -examination of liver size - transaminases, bilirubin -at 1 year: - transaminases, bilirubin -total proteins -HBs antigen 2. Exclusion from blood donation for the entire life

  40. 3) Other measures - vaccination, revaccination in the outbreak or among population • immunoglobulin-prevention and chemo-prevention • tests for population to evaluate the receptivity (ex. IDR for tuberculin) • special measures - temporary cessation of activity in some areas of public interest - health education

  41. III. Verifying and monitoring the efficiency of hygieno-sanitary and anti-epidemic measures Control of the way each doctor/nurse undertakes the proposed measures Determination of the surveillance period → maximum duration of the disease incubation period (calculated from the last case) Date and person which will declare the outbreak eradication, and the analysis of the actions taken (preventional programmes).

  42. IV. Preparation of the epidemiological inquiry sheet • The epidemiological inquiry sheet (EIS) = the most important methodological document elaborate at the occurrence of the transmissible disease • Used for epidemiological data collection, but also as a forensic document • Base for the Reporting System of Notifiable Diseases • in TD ~ has 7 chapters: - information about the ill person - pathogenic agent source - ways of transmission - receptivity level - intervention of the favouring factors - prevention and control measures - conclusions (source ~ nominal/non-identified; MWT; measures taken; duration of the outbreak surveillance).

  43. Type A VIRAL HEPATITIS Model

  44. I. The Epidemiological Process Virus source: • Humans - ill ~ children < 15 years; - carrier: pre-infectious (very contagious through his/her feces along 8-10 days before the onset of the disease); healthy (persons in close contact with the ill or pre-infectious carrier); post-infectious (eliminates small doses of virus for a few days of the convalescence) • Animals ~ non-human primates (monkeys). ~ type A hepatitis virus is eliminated through feces or blood (viremia)

  45. I. The Epidemiological Process Ways of transmission: • direct - in communities with a low level of hygiene - natural (floods, earthquake) or social (war) disasters - sexual contact - blood transfusions • indirect - food (seafood) - contaminated water, objects, hands, flies - rats (who mechanically circulate the virus)

  46. I. The Epidemiological Process Receptivity: • general ~ for persons which don’t have specific antibodies; • passive immunity (transplacental) ~ very evident because almost all women at fertility age have high levels of antibodies (repeated immunizations with small doses of virus along their lives). Favouring factors: crowd and non-hygienic behaviour.

  47. II. Control measures in VHA outbreak Measures for ill people: • detection; • hospital isolation; • nominal reporting; • decontamination of the outbreak with substances containing chlorine. Measures for suspects: • the same as in the case of the ill people until the diagnosis is clarified.

  48. II. Control measures in VHA outbreak Measures for contacts: • isolation at home • epidemiological, clinical and laboratory surveillance, for 30-40 days • excluded from blood donation for 6 months • standard immunoglobulin Measures for convalescents: • follow up for6 months • clinical and laboratory examination: liver size, transaminases, bilirubin • excluded from blood donation for the entire life

  49. B. Special epidemiological investigations any epidemiological investigation outside the operationalone used in epidemiological surveillance activities they refer to certain indicators: - morbidity, mortality, incidence, prevalence - extensivity and severity of an epidemic - immune background of the population

  50. OBJECTIVES 1. Measuring the morbidity 2. Study of the natural history of the disease 3.Health status characteristics → normal values are those: • located in the median interval (statistically normal) • observed for people without morbid manifestations (clinically normal) • proven by previous studies as being the normal status of the individual 4.Formulating and checking the aethiological hypotheses

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