Disease Detectives(Full)

Hippocrates (460 BC

365 BC)

Black Death Pandemic (Oct 1347–1351)

Killed 50% of Europe

Antoine van Leeuwenhoek (1632)

Father of microbiology and first person to observe cells

John Graunt (1662)

London haberdasher and councilman who published a landmark analysis of mortality data

James Lind (1740)

Designed first experiment using a concurrently treated control group while studying scurvy (determined limes prevent scurvy)

Edward Jenner (1790)

Developed the smallpox vaccine using cowpox clinical trials

William Farr (1800)

Father of modern vital statistics and surveillance; built upon Graunt's work

John Snow (1813)

Father of field epidemiology; formed and tested hypothesis on cholera as waterborne transmission

Ignac Semmelweis (1818)

Father of hand washing

Louis Pasteur (1822)

Recognized bacterial cause, developed anthrax and rabies vaccines, established germ theory

Joseph Lister (1827)

Father of antiseptic surgery

Robert Koch (1843)

Formalized standards (postulates) to identify organisms with infectious diseases

Florence Nightingale (1853)

Founder of modern nursing; made significant sanitary reforms during the Crimean War

Mary Seacole

Opened the British hotel in Balaclava during the Crimean War, tending to British soldiers

Edgar Sydenstricker (1881–1931)

Pioneer public health statistician; helped shed light on true causes of pellagra

Jonas Salk (1914)

Created the polio vaccine in February 1955

Flu Pandemic (March 1918 – April 1920)

Major global influenza pandemic

Joseph Goldberger (1920)

Published a descriptive field study showing the dietary origin of pellagra

Alexander Fleming (1928)

Discovered penicillin and its potential in treating bacterial infections

William Gaunt (1937)

Gathered London morbidity data to understand how age, race, occupation, and gender affect health

Mantel and Haenszel (1959)

Developed a statistical procedure for stratified analysis of case-control studies

MacMahon (1960)

Published first epidemiologic text with a systematic focus on study design

DA Henderson (1966)

Known for eradicating smallpox and establishing the WHO Expanded Program on Immunization

Carlo Urbani (2003)

Discovered SARS; WHO expert in Hanoi, Vietnam

WHO Director

Dr. Tedros Adhanom Ghebreyesus

CDC Former Director

Susan Monarez, O’Neil

CDC Acting Director

Jay Bhattacharya

4 Steps to Solve Health Problems

1) Data Collection (Surveillance); 2) Assessment (Inference); 3) Hypothesis Testing (Determine how and why); 4) Action (Intervention)

Natural History of Disease

Progression of a disease process in an individual over time without treatment from pathological onset to resolution (recovery or death)

Role of Surveillance

Assess health status, detect change in disease trends/practices, data collection for planning/monitoring/evaluation, early warning & outbreak detection

Limitations of Surveillance

Dependent on reporting (underreporting), reporting inconsistency, unrepresentative data, takes time, not a standalone solution

5-Step Surveillance Process

Data collection, data analysis, data interpretation, data dissemination, link to action

Active Surveillance

State/local officials actively search for info by contacting health providers/labs; labor-intensive, timely, and accurate

Passive Surveillance

Healthcare providers/labs initiate reporting to officials; simple and easy, but prone to underreporting and inconsistency

Sentinel Surveillance

Deliberately involves a limited network of carefully selected reporting sites (e.g., large hospitals) for high-quality data; not for rare diseases

Syndromic Surveillance

Relies on individual and population health indicators detectable before confirmed diagnoses; early detection and collaboration

5 Stages of Infectious Disease Progression

1) Incubation stage, 2) Prodromal stage, 3) Acute stage, 4) Convalescent period, 5) Resolution

Incubation Stage

Pathogen actively replicates without producing symptoms (hours to years)

Prodromal Stage

Initial appearance of vague, flu-like symptoms

Acute Stage

Maximum impact of infectious process; rapid proliferation and specific symptoms

Convalescent Period

Infection is contained/eliminated, damaged tissue repaired, symptoms decrease

Resolution Stage

Total elimination of pathogen, no residual symptoms

Scientific Method for Disease Detectives

Obtain background info, define problem, formulate hypothesis, develop study, collect data/observations, evaluate results, refine hypothesis, formulate conclusions, report results

Cluster vs. Outbreak

A cluster is a spatiotemporal grouping of cases; an outbreak has a common agent and cases are higher than expected

BRFSS

Collects data from U.S. residents regarding health-related risk behaviors and chronic health conditions

Chronic Disease

A disease or condition lasting 3 months or longer that may worsen

Cluster

An aggregation of cases closely grouped in time and space

Communicable Disease

Infectious diseases that spread specifically from person-to-person or animal-to-person

Droplet Nuclei

Residue of droplets of infectious agents

Etiology

Study of the cause of a disease

Epidemiology

Study of how often diseases occur in different groups of people and why

FATTOM

Food safety mnemonic (Food, Acidity, Temperature

Food Borne Illness

Illness or disease that travels through unsafe foods

Fulminant

Occurring suddenly and with great intensity or severity

Fungi

Plant-like organisms that can be pathogens and cause infections

Hawthorne Effect

Individuals modify their behavior due to awareness that they are being studied

Holoendemic

Endemic affecting younger population/children (vs. hyperendemic for all age groups)

Iatrogenic

A disease or infection gained from being treated in a healthcare setting

Incubation Period

Time between contact with a pathogen and first showing symptoms

Index Case

First documented patient in a disease epidemic or epidemiological study

Infectivity

Proportion of exposed persons who become infected by infectious agents

Infectious Dose

Amount of pathogen required to cause disease

Latent Period

Time between contact with a pathogen and being able to spread it

Mode of Transmission

How a pathogen moves from one body to another

Morbidity

Rate of disease in a population

Mortality

Rate of death in a population

Mortality Rate

Number of deaths due to a disease divided by total population

Mycology

Study of fungi

NCHS

National Center for Health Statistics

NHANES

National Health and Nutrition Examination Survey

Pathogenicity

Proportion of infected persons who develop clinical disease

Portal of Entry / Exit

Opening where a pathogen enters or exits the body

Primary Case

Original case in a population (does not have to be the index case)

R Nought (R₀)

Reproductive number indicating how contagious a disease is

Reservoir

Area where agents can thrive and reproduce

Respiratory Droplet

Disease transmission through water or mucus droplets from coughs/sneezes

Risk

Probability that an individual will be affected by or die from an illness/injury

Sequelae

Aftereffect of a disease or injury

STD

Disease transmitted through sexual intercourse or mixing/exchanging blood

Surveillance

Systematic and ongoing collection, analysis, interpretation, and dissemination of health data

Vaccine Efficacy vs. Effectiveness

Performance in a controlled trial setting vs. real-world setting

Vector

Animal that can transfer a pathogen without necessarily having it

Virulence

Severity of clinical disease or degree of damage leading to death

Incidence

Number of new instances of disease in a population over a given time period at risk

Prevalence

Number of affected persons in the population at any given point in time

P = I * D Formula

Prevalence equals Incidence multiplied by Duration

Cross-Sectional Study

Survey or health questionnaire ('snapshot in time'); fastest, least expensive, good for multiple outcomes, but time-order confusion

Case-Control Study

Compares people with and without a disease to find common exposures; good for rare diseases/long latency, measures Odds Ratio

Cohort Study

Compares people with and without exposures to see what happens; most accurate observational study, correct time sequence, measures Relative Risk, expensive

Ecological Study

Comparisons of geographical locations using pre-existing data; easy/inexpensive, but cannot examine causality

Randomized Controlled Trial (RCT)

Gold standard study design (human experiment); most scientifically sound, but expensive and unethical for harmful exposures

Quasi Experiments

Research similar to RCTs but lacking random assignment; higher external validity, but harder to control confounding variables

Case Reports / Series

Observational design tracking individuals with a shared disease/exposure over time without a control group; critical for rare diseases

Animal Research

Scientific study of animals in labs for biological knowledge; allows molecular/cellular study, highly regulated and raises ethical issues

Meta-Analysis

Statistical method combining and synthesizing quantitative data from multiple independent studies using a weighted average

Systematic Review

Scholarly synthesis of evidence using explicit, reproducible methods to minimize bias (often following PRISMA)

Primordial Prevention

Risk factor reduction targeted toward an entire population through laws and social/environmental conditions

Primary Prevention

Early intervention to avoid initial exposure to a disease agent and prevent process from starting

Secondary Prevention

Screening and instituting treatment during the latent stage to prevent progression to symptoms

Tertiary Prevention

Intervention during the symptomatic stage to arrest, slow, or reverse disease progression