Public Health Unit 3

Exposure

anything that can cause illness

Exposure Example

whatever bacteria that is in a cough, factor that causes autism

Fetal Alcohol Syndrome Exposure Example

pregnant women drinking alcohol, not the alcohol itself

n

number of people in a particular study (sample of population)

Case Study n

n=1 studied one person

Epidemiology

study of distribution and determinants (exposures) of disease frequency in human populations, diagnostic discipline of public health, evaluates effectiveness of medical and public health interventions

Etiology

investigates causes of diseases

Epidemiology Definition

identifies trends in disease occurrence

What function is epidemiology a part of

assessment function

Epidemiology Work Origin

epi: upon, demos: people, logos: study

Endemic

disease that is expected and can predict rates

Endemic Example

flu- weather related, seasonal

Elimination Example

WHO declares measles eliminated

Eradication Example

smallpox eradicated when endemic rate was 0

Outbreak

when actual cases gets larger than endemic rate

Surveillance

monitor disease rates

Epidemic Surveillance

looking for an increase of cases/gathering data

SARS

severe acute respiratory syndrome (2002)

MERS

Middle East respiratory syndrome (2012)

COVID-19

SARS-COV2 caused by corona virus (2019)

Outbreak Investigation

trying to find source

Shoe Leather Investigation

physically going to talk to people

Chronic Disease Monitoring

hard to monitor ex. smoking, bad nutrition

Father of Epidemiology

John snow, 1st epidemiologist (cholera)

Sanitation Definition

ability to clean water, able to separate waste from potable drinking water

Framingham Study

one of the 1st most long running studies, MA heart disease

What did the Framingham Study Determine?

smoking is bad and can lead to chronic diseases based on location

Prevention Example

framingham study, etiology (causes), monitors diseases

MMWR

CDC publishes statistics on diseases currently

Mortality (deaths)

causes or contributors given range

Morbidity

how many people are affected?

Calculate Incidence

number of new cases this week

Calculate Prevalence

all known cases total

Calculate Total Cases

incident - mortality

Population Attributable Risk

portion of people who got disease from one exposure

Example of Population Attributable Risk

extent to which smoking impacts (effect size)

Distribution in Public Health

who/when where

Determinants

why

Research Approaches

ways of knowing, differs based on curves

Epidemiological Curves Classification

each box represents 1 case

Point Source Curve Definition

outbreak, spike that goes away, not endemic

Point Source Example

cyclospora

Point Source Curve Image

Propagated Source Definition

cannot pinpoint 1 exposure, represents waves

Propagated Source Example

influenza type illness (iti)

Propagated Source Image

Continuous Source Definition

cases start day 1, small variation, represent pattern of disease acquisition

Continuous Source Example

water source that causes cancer, heart disease

Continuous Source Image

Intermittent Source Definition

1 specific exposure, spikes, represent waves

Intermittent Source Example

infected food handler with Hep A that only works some days

Intermittent Source Image

Step 1 of Epidemiological Process

confirm outbreak diagnosis

Step 2 of Epidemiological Process

Form outbreak control team

Step 3 of Epidemiological Process

Define a case- must meet clinical criteria to count as a case

Step 4 of Epidemiological Process

identify cases and obtain info (shoe leather)

Step 5 of Epidemiological Process

describe data by time, place, person

Step 6 of Epidemiological Process

Develop hypothesis

Step 7 of Epidemiological Process

Test hypothesis, analytical studies (must be tested in investigational location (lab testing))

Step 8 of Epidemiological Process

Additional Studies

Step 9 of Epidemiological Process

Implement control measures

Step 10 of Epidemiological Process

communicate results

What are the three types of studies?

intervention/experimental design, cohort, case-control

Intervention/Experimental Design Description

gives best most precise results (gold standard)

Drawback of Intervention/Experimental Method

not possible in a lot of cases because of ethical standards

Example of Why Experimental Goes Against Ethical Standards

to test HIV you cannot ethically or legally inject people with HIV

Key Point in Intervention/Experimental Design

must have at least two groups (experimental and control) that are randomly assigned

What role does time play in intervention/experimental design?

track before, during, after, intervention

What is the only factor that can determine cause and effect in intervention/experimental design?

time

Cohort Definition

naturally occurring exposure, similar subjects, one or more groups

What factor can show cause and effect in cohort study but not as good as intervention?

time

What key point about the exposure is needed in cohort study?

must be tracked with something that will not cause dropout

Benefits of cohort study

study things that may cause cancer or alcohol effects in ethical manner, good for rare exposures

Disadvantages for cohort study

hard to study rare diseases, differential dropouts

Case-Control Study Description

match 1 person to another person (best for rare diseases)

Can cause and effect be determined in case-control?

not really because exposure has already occurred

Case-Control Study Example

siblings, 1 pregnant takes Tylenol and the other pregnant one doesn’t, compare autism rates

Dose Response Relationship

the more of something you give, the more of an effect you would see

Intervention Problem

subjects may not follow prescribed behaviors throughout study period

Cohort Study Problem

sometimes it is hard to isolate which of many factors are responsible for health differences

Case-Control Problem

control group may not be truly comparable, errors may exist in reporting or recalls

Error Definition

random variation and confounding variables (variables that affects outcome)

Bias Definition

selection bias, reporting bias or recall bias (not remembering correctly)

Validity Definition

strong association, dose response relationship, known biological explanation, large study population and consistent results from several studies

Epidemiology Definition

science that helps us uncover truths about health