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HS 370 Epidemiology Lesson 1

by: Cindy Cannon

HS 370 Epidemiology Lesson 1 HS 370

Cindy Cannon

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Basic Epidemiology
Watson, Tyler A.
Class Notes
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This 8 page Class Notes was uploaded by Cindy Cannon on Wednesday February 10, 2016. The Class Notes belongs to HS 370 at Brigham Young University - Idaho taught by Watson, Tyler A. in Fall 2016. Since its upload, it has received 14 views. For similar materials see Epidemiology in Nursing and Health Sciences at Brigham Young University - Idaho.

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Date Created: 02/10/16
Epidemiology Lesson 1 Epidemiology: the study of the distribution and determinants of health- related states or events in specified populations and the applications of this study to the control of health problems. Assumptions  Disease and illness have a “cause” o Pathogens: (Bacteria, Virus, Fungus, Parasite) o Mutations: (Cancer, birth defects, etc.) o Irritants/Allergies: (silica, CO asbestos) o Contaminants  Diseases do not arise in a vacuum (Gordis, 1996)  Illnesses arise from an interaction of human beings with the environment  Epidemiology can explain the importance of those interactions Pathogens/Contaminants tend to behave the same way in similar circumstances o They grow at the same rate at the same temp o They die if expose to the “right” things o Each pathogen/contaminant presents in the human body with distinct patterns o Pathogens don’t cause fever in one person and headache in another. The symptoms they cause will be replicated no matter the person infected 3 Ways Pathogens Enter the Body (Mode of Entry) o Eat it o Breathe it  Through mucus membranes… includes conjunctiva and mucus membranes of the genitourinary tract o Inject it Historical Uses of Epidemiology Old Testament Leviticus 13:2-8 o The Law of Moses: If you have scabs with white features you must go to the priest to determine what your illness is and if he suspects you with leprosy then they should be shut him up (quarantine) and after the 7 days the priest should look at him again to see if the illness has spread and if it did then it is leprosy and if it doesn’t then it is a scab. And if the man has leprosy then he must be permanently separated from the community in order to keep the illness from spreading. Epidemiology Lesson 1 1 John Snow o Creator of the first “Spot Map” o Found many getting E. Coli and began to investigate where the people in the area that were getting sick were getting their water. He found that more of the infected people were getting their water from the same area. He found one of the water pump and concluded that it was what making people were sick. However after he began to preach his findings to the people no one would believe him, so he ended up breaking the handle on that particular water pump and weeks after doing so the community saw a dramatic decline in E. Coli cases Edward Jenner o Was the first man you created the first vaccine for smallpox, by infecting a young boy with cowpox. He did this because he found that those who had already had cowpox weren’t getting smallpox. He then repeated the process by infecting the boy with smallpox. The reason that he chose a younger man because it would help ensure that he wasn’t exposed to smallpox already. o How he did it was that he would cut an small opening in the young boy’s arm then would poke the pus fill boil of one who was infected and then spread the puss into the young boy’s arm were the cut was. Why Epidemiology?  Assess the community  Making decisions  Completely the clinical picture  Finding the cause What We Do  Actions conducted after the epidemiology has been done o Linkages (conclusions based on analytical studies)  Policy development How We Do It  Count stuf o Not just the number of cases but the rate of cases in a particular area  Just comparing the number on skin cancer cases from Boise and Seattle isn’t vialed because of the population in Seattle being much higher then Boise  Compare stuf Epidemiology Lesson 1 2 o Seeing whether a particular sub-group rate is particular higher then others for a particular health risk. Study  Epidemiology is data-driven and relies on a systematic and unbiased approach to the collection, analysis, and interpretation of the data.  Basic epidemiology methods tend to rely on careful observations and use of valid comparison groups to asses whether what was observed, such as the number of cases of dieses in a particular are during exposure among persons with disease, difer from what might be expected o Epidemiology is a quantitate discipline that relies on a working knowledge of probability, statistics, and sound research methods o Epidemiology is a method of causal reasoning based on developing and testing hypothesis grounded in such scientific fields as biology, behavioral sciences, physics and ergonomics to explain health-related behaviors, states and events Distribution  Epidemiology is concerned with the frequency and pattern of health events in a population o Frequency refers to not only the number of health events such as the number of cases of meningitis or diabetes in a population, but also the relationship of that number to the size of the population o Patterns refers to the occurrence of health-related events by time, place and person  Descriptive Epidemiology: characterizing health events by time, place, and person Determinants  Epidemiology is also used to search for determinants, which are the causes and other factors that influence the occurrence of the disease and other health-related events o They assess whether groups with diferent rates of disease difer in their demographic characteristics, genetic or immunologic make-up, behaviors, environmental exposure, or other so-called potential risk factors Health-Related States or Events  Epidemiology was originally focused exclusively on epidemics of communicable disease but was subsequently expanded to also Epidemiology Lesson 1 3 address non-communicable infections and environmental and occupational health Specified Population  One diference between an epidemiologist and a clinician is that the clinician is concerned with the health of an individual and the epidemiologist is concerned with the collective health of the people in a community or population Application  The epidemiologist uses the scientific methods of descriptive and analytic epidemiology as well as experience, epidemiologic judgment, and understanding of local conditions in diagnosing the health of proposing appropriate, practical, and acceptable public health interventions to control and prevent disease in the community. Core Epidemiologic Functions  Public Health Surveillance: an ongoing systematic collection analysis interpretation, and dissemination of health data to help guide public health decision-making and action o Surveillance Cycle  Active Surveillance: actively seeking cases that would have not actively come to you  Passive Surveillance: cases, which are delivered to you, which you wouldn’t discover otherwise  Field Investigation: one of the first actions that results from a surveillance case report is an investigation by the public health department, whether by phone or travelling to the area  Analytic Studies: Surveillance and field investigation are usually sufficient but sometimes-analytic studies employing more rigorous methods are needed o The hallmark of an analytic epidemiologic study is the use of a valid comparison group  Design: includes determining the appropriate research strategy and study, design, writing Epidemiology Lesson 1 4 justifications and protocols, calculating sample sizes, deciding on criteria for subject selection, choosing an appropriate comparison group, and designing questioners.  Conduct: involves securing appropriate clearances and approvals, adhering to appropriate ethical principles, abstracting records, tracking down and interviewing subjects, collecting and handling specimens and managing data  Analysis: begins with describing the characteristics of the subjects and progresses to calculation of rates, creation of comparative tables, and computation of measures of association, tests of significance, confidences intervals, and the like  Interpretation: putting the study finding into perspective, identifying the key take-home message, and making sound recommendations.  Evaluation: the process of determining as systematically and objectively as possible the relevance, the efectiveness, efficiency, and impact of activities with respect to established goals o Efectiveness: the ability of a program to produce the intended or expected results in the field o Efficiency: the ability of the program to produce the intended results with a minimum expenditure of time and resources  Linkages: during an investigation an epidemiologist usually participates as either a member or the leader of a multidisciplinary team o To promote current and future collaboration, the epidemiologists need to maintain relation ships with staf of other agencies and institutions.  Policy Development: epidemiologists who understand a problem AND the population in which in occurs are often in a uniquely qualified position to recommend appropriate intervention. The Epidemiologic Approach  In very simple terms the epidemiologist o Counts cases or health events, and describes them in terms of time, place and person o Divides the number of cases by an appropriate denominator to calculate rates o Compares the rates over time or for diferent groups of people Epidemiology Lesson 1 5  Defining a Case: before counting cases, the epidemiologist must decide what to count, that is, what to call a case o Case Definition: a set of standard criteria for classifying whether a person has a particular disease, syndrome, or other health condition Components of a Case Definition (for outbreaks investigations) o A case definition consists of clinical criteria and, sometimes, limitations on time, place, and person  The clinical criteria usually include confirmatory laboratory test, if available, or combinations of symptoms (subjective complaints), signs) objective physical findings), and other findings o Confirmed: present a list of symptoms and then provided testing for those with those symptoms to see if the lab confirms it. o Probably: suspect with symptoms and has a epidemiological link with other’s who have the illness o Suspect: those who have the symptoms but no epidemiological link to others  Criteria in Case Definitions: case definitions may have several sets of criteria, depending on how certain the diagnosis is o A case might be classified as suspect or probably while waiting for the laboratory results to become available, then once the laboratory provides the report the case can be reclassified as either confirmed or “not a case”  Modifying Case Definitions: case definitions can also change over time as more information is obtained  Variation in Case Definitions: case definitions may also vary according to the purpose for classifying the occurrence of a disease o For such rare but potentially severe communicable disease, for which is important to identify every possible case, health officials use a sensitive case definition, which is broad or “loose” in the hope of capturing most or all true cases  Using Counts and Rates: for some purposes, the counts must be put into content based on the population in which they arose o Rates are measures that relate the number of cases during a certain period of time (usually per year) to the size of the population in which they occurred. Descriptive Epidemiology: covers time, place and person  Time: the occurrence of disease changes overtime o Secular (long-term) Trends: graphing the annual cases or rate of a disease over a period of years shows long-term or Epidemiology Lesson 1 6 secular trends in the occurrence (increasing, decreasing or essentially flat), help them evaluate programs or make policy decisions, infer what caused an increase or decrease in occurrence of a disease, and use past trends as a predictor of future incidence of disease o Seasonality: disease occurrence can be graphed by week or month over the course of a year to who it’s seasonal pattern, in any o Day of Week and Time of Day: analysis at these shorter time periods of particularly appropriate for conditions related to occupation or environmental exposures that tend to occur at regularly scheduled intervals o Epidemic Period: to show the time course of a disease outbreak or epidemic, epidemiologists use a graph called an epidemic curve  Place: describing the occurrence of disease by place provides insight into the geographic extent of the problem and it’s geographic variation  Person: because personal characteristics may afect illness, organization and analysis of data by “person” may use inherent characteristics, biological characteristics, acquired characteristics (marital status), activities or the condition under which a person lives Analytic Epidemiology  Epidemiologists can use descriptive epidemiology to generate hypotheses but rarely to test them. For that, they must turn to analytic epidemiology o The key feature of analytic epidemiology is a comparison group  Epidemiologist use analytic epidemiology to quantify the association between exposures and outcomes and to test hypotheses about casual relationships Epidemiologic studies fall into 2 categories: experimental and observational o Observational Studies: the epidemiologist simply observes the exposure and disease status of each study participant  Cohort Study: the epidemiologist records and separates each study participant by whether they are exposed or not, and then tracks the participants to see if they develop the disease of interest  This difers from an experimental study because, in a cohort study, then the investigation observes rather then determines the participants’ exposure status Epidemiology Lesson 1 7 o Prospective Cohort Study: studying exposure status as is it happening in the present o Retrospective Cohort Study: studying exposure status by researching the participants personal history  Case-Control Study: investigators enroll a group of people with disease (case) and a group without disease (control) and compare previous exposures between them  If the amount of exposure among the case group is substation ally higher than the amount you would expect based on the controlled group, then the illness is said to be associated with exposures o The diference between a case-control study and cohort study is that a case- control study separates the people into 2 separate groups based on whether or not they have the disease or not and a cohort study separates the people into 2 separate groups based on whether or not they have been exposed to the factor that may cause the disease.  Cross-Sectional Study: a sample of people from a population is enrolled and their exposures and health outcomes are measured simultaneously  Clinical Trials: is any research study that prospectively assigns human participants or groups of humans to one or more health-related interventions to evaluate the efects on health outcomes. Epidemiology Lesson 1 8


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