let's run up the bradford hill

#FomiteFriday

search for additional cases and clues regarding source & mode of transmission

shoe leather epidemiology

measures exposure & early biological response by 1) evaluating host characteristics 2) using biochemical markers of a positive effect to refine disease categories

molecular epidemiology

Establishes 1) a genetic part to disorder 2) relative size of that genetic effect in relation to other sources of variation in disease risk & 3) responsible genes

genetic epidemiology

1) Pathogen must be present in case of disease

2) Pathogen can be isolated from infected host & grown in pure culture

3) Pathogen must cause disease when injected into new susceptible host

4) Pathogen reisolated from new host must be same as og inoculated pathogen

kochs postulates

1) Single pathogen can cause multiple disease

2) vice versa of 1 (one disease can be caused by multiple pathogens)

3) Some pathogen only cause disease in human and can’t be cultured in a lab

exceptions of kochs postulates

entire pop affected

holoendemic

persistent, high level disease

hyperendemic

disease constantly at low incidence = little or no immunity

hypoendemic

disease caused by doctor or meds

iatrogenic

disease w unknown cause

idiopathic

denominator of person time rate

\# of people followed multiplied by # of years

indirect measurement

proxy measurement

microbes that usually do not cause disease in healthy people, but may become virulent with immunocompromised and unhealthy individuals

opportunistic pathogen

LD50

Lethal Dose. dose that causes the death of 50% of a group of test animals

MRSA stands for

Methicillin Resistant Staphylococcus

MMWR

Morbidity mortality weekly report

When was WHO founded? (Month day, year)

April 7, 1948

What is a serial interval?

Duration between onset of secondary case from primary case

What is the chain of transmission triad?

Agent, vector, host

Pros of public health surveillance (3)

Timeliness, simplicity, felxibility

Cons of public health surveillance (3)

Expensive, not reproducible

What are the 5 steps of good surveillance?

Data collection, analysis, interpretation, dissemination, action

What are the pros of passive surveillance? (3)

Cheap, good for monitoring trends over time, large-scale

What are the cons of passive surveillance? (3)

Underreporting, low sensitivity, not representative

What are the pros of active surveillance? (3)

More information, better quality, high sensitivity

What are the cons of active surveillance? (3)

High use of resources, time consuming, hard to sustain over time

What are the pros of sentinel surveillance? (3)

High-quality, fast, cheap

What are the cons of sentinel surveillance? (3)

Bad for rare diseases, won’t report stuff outside sites, bad in monitoring incidence over time

What are the pros of syndromic surveillance? (3)

Low bias, cheap, fast

What are the cons of syndromic surveillance? (3)

Low specificity, bad for big outbreaks, inaccurate

What are the 13 steps of an outbreak investigation?

Prepare for field work, establish existence of disease, verify diagnosis, form case definition, find cases systematically and record info, use descriptive epidemiology, find hypothesis, evaluate hypotheiss, reconsider, refine, re-evaluate hypothesis, compare and reconcile with lab, control/prevent measures, initiate/maintain surveillance, communicate findings

What are the 9 Bradford hill criteria?

Strength of association, consistency, specificity, alternative explanation/casuality, temporality, dose-response/biological gradient, biological plausibility, experimental evidence, coherence

Single cause cause specific effect means what?

Specificity

What does it mean to consider multiply hypothesis before saying association causal or not?

Alternative explanation/causality

What does cause/exposure must precede outcome mean?

Temporality

What does it mean to have a stronger response when there’s more exposure?

Dose-response

What does it mean to be able to alter the condition or prevent/accelerate it?

Experimental evidence

What does it mean when the association is compatible with existing theory and knowledge of past cases?

Coherence

What case compares patients to themselves?

Case-crossover

What study is risk factors known, disease not known?

Cohort

What study is disease known, risk factors not known?

Case-control

What do you use for cohort studies?

Risk ratio

What do you use to calculate case-control studies?

Odds ratio

What are the pros for cohort? (3)

Good for long term disease, good for rare exposure, assess multiple outcomes for 1 exposure

What are the cons for cohort? (3)

Bias, costly, need large population

What are the pros for case-control? (3)

Cheap, good for rare & long latency period disease, shorter

What are the cons for case-control? (3)

Unreliable information, confounding variable, can’t calculate prevalence

What do you use to calculate cross-sectional?

Prevalence

What are the pros of cross-sectional? (3)

Quick, cheap, easy

What are the cons of cross-sectional? (3)

Low response, no causality, recall bias

Selection bias, patients lost to follow up exluded

Attrition bias

Selecting people from subpop

Berkson’s (selection) bias

Bias toward belief we already have

Confirmation bias

How can confounding be prevented?

Randomization, restriction, matching

When correlation at group level doesn’t accurately represent correlation at the individual level

Ecological fallacy

When people in survey don’t include dead/ill

Late look bias

Systematic difference between reported & unreported

Reporting bias

Groups differ in ways other than exposure

Selection bias

People with severe illnesses can’t fill out survey & excluded from study

Neyman bias

Out of how many people who have the disease, how many people actually test positive?

Sensitivity

Out of all the people who do not have the disease, how many people actually test negative?

Specificity

Out of all the people who test positive, how many people actually have the disease?

PPV

Out of all the people who test negative, how many people actually don’t have the disease?

NPV

Father of modern surgery

Joseph Lister

Created polio vaccine

James Salk

Landmark analysis of mortality data

John Graunt

Made smallpox vaccine

Edward Jenner

Father of epidemiology

John Snow

Made anthrax vaccine

Louis Pasteur

Primary control example (3)

Public education, vaccine, ban products

Primordial control example (3)

Optimal diet, remove barriers to exercise, government tax on cigarettes

Secondary control example (3)

Screening, physical exam, colonoscopy

Tertiary control example (3)

Rehab, surgery, speech therapy

Quaternary control example (3)

Pull plug on patient, anti arrhythmic drug, hormone replacement therapy

Public policy to restrict spread of agent before people begin to protect against agent

Control

Reduction to 0 of incidence of infection caused by specific agent in geographical area

Elimination

Permanent reduction to 0 of worldwide incidence of infection

Eradication

Agent does not exist in nature or in lab

Extinction

What graph is this and what spread is this?

Common continuous, water borne

What graph is this and what spread is this?

Point source, foodborne

What graph is this and what spread is this?

Propagated, person-perosn

What graph is this and what spread is this?

Intermittent, sporadic

What is leading rabies vector

Bats

Why cooked food still cause harm? 3

Temperature not hot enough, toxin is heat stable, release endotoxin from dead agent

Science of causes and effects of disease

Pathology

Study of cause of disease

Etiology

Biochemical test that measures presence/concentration of macromolecule in solution through proteins/antigens

Immunoassay

A study design in which the investigator specifies the type of exposure for each study participant

Experimental

A study in which a sample of persons from a pop are enrolled and their exposures and health outcomes measured simultaneously

Cross-sectional

What study is least subject to recall bias

Prospective cohort study

Want to test a hypothesis but don’t have funding or time. Have national data on masking policies and number of students in each district. What study design do you use?

Ecological

T/F One can skip the preparing for field work step of outbreak investigation unless one is traveling.

F

You have unlimited budget and access to labs but little time.

Case control

what case

Case control

some people may be infected with SARS/CO-V and have a negative test. What source of error (bias) is this?

Misclassification bias

Vector in which the parasite multiplies in numbers/undergoes developmental change in life cycle

Biologic vector