Epidemiology Exam 1 Review PDF

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Exam review for exam 1 given by professor...

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Epidemiology Exam 1 Review -

Introduction to epi o Definitions of epi  Study of the dist. of disease or a physiological condition in human populations and of the factors that influence this distribution  The study of disease occurrence in human poulations  Study of the occurrence and distribution of disease or other health-related conditions in human populations  Study of the distribution and determinants of health-related states or events in specified populations and the application of this study to the control of health problems o Nature of life-expectancy improvements since HG days  We have increased overall life expectancy o Source of above improvements  Hygiene, better diet, o At what stage of life do most above increases occur?  During early life and midlife o Stages of disease prevention  Primary- prevention, preparing people to be healthy and not get sick in the first place  Secondary- treatment, managing a disease or preventing further demise and comorbidities  Tertiary- accommodation, making people with disease comfortable for the remainder of their lives o Semmelweis’ discovery  Women were dying at alarming rates of “childbed fever” shortly after giving birth  While running a women’s clinic that was also a site for autopsies of the mothers that passed away, he noticed that a second clinic that did not perform autopsies did not have the same mortality rates  He decided that the women in clinic 1 were dying because the disease was being transmitted on the doctors hands from the cadavers to the genitals of the new mothers. o Why did it take so long for Semmelweis’ ideas to be accepted?  It was very political to accuse doctors of killing their own patients, essentially.  He also never published his findings, so it wasn’t until way later that someone else published findings that rules were put in place permanently o Have we reached adequate hand-washing and hygiene to prevent nosocomial transmission of disease today?  On the healthcare provider’s side, we might be close. But it is hard to control patients and hospital visitors.

o Difference between descriptive and analytic, observational and experimental o Issues with loannidis paper  What paper o Why human populations are harder to study than physical and natural phenomena  idk o What are the 5 models of disease causation discussed in lecture  Host, agent, and environment model  There is a host where an agent lives/replicates and an environment where the agent normally resides  The nature or characteristics of each factor affects how or if the disease is transmitted successfully  Person time place model  Time and place are used to link persons  Being able to tie exposures between time periods and shared spaces between people is useful  Exposure outcome model  Exposure- likelihood of exposure and likelihood of outcome after exposure  Simple model connects exposure to an outcome  Cause-effect model  Establish cause and effect between the exposure and outcome  Math and statistical models  Mathematical representations of biologic processes  Mathematical approach to find and understand patterns in data  Which can contribute direct evidence for disease causation  Cause effect model?  Which models may not work in certain situations  idk  Examples of factors in a host-agent-environment  Agent- biological organism, environment- vectors, population density, host- age, sex, race/ethnicity  What limits does using person-time-place put on what we can do with the results  We cannot apply to future or past instances because it only refers to that specific time and place  Examples of exposure-outcome  ??  Simple definitions of each of the 9 types of possible causal evidence  Strength of association (bio stats)  Temporal relationship (biostats)  Dose-response relationship/gradient (pharmacology, bio, social science)  Biological plausibility in existing scientific theory (bio, med)

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Consistency (can be and has been replicated; biostats for metaanalysis) Specificity of exposure (clinical med and social science) Experimental evidence (biostats) Analogy (scientific literature)

Disease Dynamics o Major types of disease transmission  Direct  indirect o Direct and indirect modes of disease transmission in the book  Direct- through person to person contact  Indirect- through common vehicle or vector o How do the classes of severity of certain diseases fit together (textbook)?  ?? o How do latent periods, infectious periods, and incubation periods fit together with clinical disease (will be a matching question)  Latent period- when you have the disease but are not yet showing symptoms  Infectious period- when you are not sick yet but are spreading it to others  Incubation period- when the agent replicates or grows  It becomes clinical once the symptoms start showing up o Components of attack rate and how to calculate it  Number of people at risk who do develop the disease divided by number of people at risk during a specified period of time o What is reproductive rate  R(knot)  The number of secondary infections caused by one infected individual in a susceptible population  What do different levels of it mean  Rknot greater than 1 means epidemic  “ equal to 1 means endemic  “ less than 1 means extinction  What are its three constituent components  B, k, and D  Attack rate, # of susceptible contacts per time, and duration of infectiousness o Examples of different epidemic transmission types from lecture  ?? o Herd immunity and how it works/problems with its achievement and calculation  When unvaccinated members of a population are protected from disease because of large numbers of vaccinated individuals reducing transmission  It is determined by Rknot

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Problems- it requires very high levels of vaccinations since people are not random. These levels are unrealistic in most populations  Other problem is that the agent must be restricted to one host species and the transmission must be relatively direct. No resevoirs. Calculation for a Herd Immunity Threshold (HIT) from R(knot)  P,(HI) = 1- (1/Rknot) Relationship between reproductive rate and necessary vaccinations needed to achieve herd immunity  If the reproductive rate was 18, you would need 92 percent immunity to block transmission. And 18 is an unrealistic value to begin with. How the idealistic nature of R0 in an immune naïve population is complicated by the nature of current immunity in the real world (with and without vaccines; with natural immunity; with acquired immunity from similar infections like influenza strains; due to non-random distributions of vaccinations in populations versus HIT calculations, etc.).  Describe who is and who is not at risk when herd immunity falls  When herd immunity goes down, the unvaccinated people are at risk. Whether by choice or by physiological restrictions. Children, the elderly, the immunocompromised. Proximal control of ID and what does it require  Control source of pathogen  Modify host immune response (vaccines and immunotherapy)  Interrupt transmission (condom use, control vector) What is the spectrum of disease  From healthy disease onset  symptoms  seek care diagnosis  treatment  outcome Why is stopping an epidemic early so important?  Because of the incubation period where the disease is spread rapidly occurring toward the beginning. We want to overall decrease the number of people out there spreading the disease. Are all stages of epidemic equally risky?  No? What does the graph of an epidemic look like over time when tracking active disease?  ? What are the names for patients who: have new disease, no longer have active disease, and who get exposed during stages of an epidemic?  Case, removed, and contact Three stages of SIR epidemic model  Susceptible, infected, removed Types of physical transmission of diseases (Ppt)

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 Airborne, droplet, saliva, fecal-oral, sexual contact, bodily fluids o How does physical transmission type determine PUBH prevention and remediation steps for an epidemic?  An STD needs a different approach than an airborne disease. STDs have a larger behavioral component than an airborne disease. o How is remediation of an epidemic different for HIV versus smallpox due to physical transmission  They have different transmission rates  HIV is more related to behavior. Smallpox is airborne and thus the approach is not primarily about changing the behavior of patients. Epidemic Investigation o Five steps of an epidemic investigation, application to John Snow’s work 1. Define the epidemic a. Determine the number of cases b. Determine the population at risk c. Calculate attack rates 2. Examine the distribution of cases in terms of person, time, and place a. Epidemic curve b. Maps c. Tables stratified by demographics and other factors 3. Develop hypotheses for the cause or source of an epidemic a. Existing knowledge of the disease b. Analogy to other diseases 4. Test the hypotheses a. Case-control b. Cohort studies (retrospective and prospective) 5. Recommend control measures o How did maps help John Snow  Maps helped him understand the geographic nature of the spread of the disease  What did he include on the maps  the incidence and prevalence of cholera in certain areas  What step helped him stop the next epidemic  Removing the water pump handle helped stop the current one. Getting rules in place about reporting/surveillance helped prevent further epidemics. o Incidence proportion vs incidence rate, what dimensions do they vary by?  Incidence proportion is the incidence number over the population. Incidence rate is in a given time period.  The dimension they vary in is time. Epi Study Designs o Breakdown of epidemiologic study designs with:  Case report

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Good for making community aware of a disease, good for surveillance data, stimulates research  Cons: cannot infer correlation or causation, subject to reporting bias  Case series  Same as above  Cross-sectional  Measures a single point in time  Pros: efficient, quick assessment, leads to further investigation, yields prevalence estimates  Cons: cannot predict, limited use in epidemic investigations, no incidence data, does not establish sequence of events (childhood obesity and watching TV)  Case-control  Single instance of observation, exposure determined retrospectively  Pros can lead to determination of causation or correlation  Cons: finding cases, publication bias occurs if desired results are not found,  Cohort  Long time period  Pros: studying multiple outcomes, defining incidence of disease, sequence of events (cause and effect) can be determined, allows measurement of exposures more completely  cons: large sample size needed, requires follow up, expensive and time consuming, attrition very problematic  Ecologic  Unit of analysis is the group not individual  Correlations obtained between exposure rates and disease rates among different groups or populations  Ecologic comparison or ecologic trend study  Randomized clinical trial  Community randomized trial/field trials  Meta-analysis o what variable is manipulated in an experimental study design? Why might it be unethical in some human cases o how does sampling of exposures and outcomes vary in cohort versus case control studies o what study types deal with incidence? Prevalence? o What study types deal with time o What is the ecological fallacy Descriptive Epi o 5 objectives of epi

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Common problems with measuring demographic variables Common measure of place and time Common uses of descriptive epi What is disease surveillance, how is it done, and by what entities 9 uses of public health surveillance from lecture and examples Active surveillance vs passive Universal vs sentinel reporting Compoulsory vs voluntary reporting Measurement in the census (age, race/ethnicity, etc) What is difficult about lead exposure? Vitamin A?...