How epidemiology grew from one doctor's hunch into a global science
Epidemiology's roots stretch back almost 2,500 years, but it didn't become the organized science we know today until the last 170 years or so. Here are the milestones every Disease Detective should recognize.
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~400 BC
Hippocrates
Tied disease to environment & behavior, not angry gods: the “father of medicine”
JG
1662
John Graunt
Found patterns in London’s death records: the “father of demography”
1747
James Lind
Ran one of the first controlled trials: citrus cured scurvy; later, lime-juice rations earned British sailors the nickname “limeys”
1796
Edward Jenner
Used material from cowpox sores to protect people against smallpox: the first vaccine
1800s
William Farr
Built modern vital statistics: the “father of modern surveillance.” His death categories led to the ICD
1847
Ignaz Semmelweis
Showed that doctors washing their hands cut deaths from childbed fever
1854
John Snow
Mapped a cholera outbreak to one water pump, building the case against miasma ("bad air") theory: "father of field epidemiology"
1854–56
Florence Nightingale
Improved hygiene & sanitation for wounded soldiers during the Crimean War, cutting death rates: founder of modern nursing
1860s–80s
Louis Pasteur
Helped prove germ theory; invented pasteurization (heating to kill microbes) and made vaccines for anthrax and rabies
1880s
Robert Koch
Wrote the first set of rules (Koch's postulates) for proving a microbe causes a disease
1946–1980
CDC & Eradication
CDC founded (1946) to fight malaria; smallpox eradicated (1980), the first disease ever wiped out
2001–today
Modern Era
Genomics, bioterrorism readiness, and real-time digital surveillance
Big Outbreaks Through History
Tests ask you to put these in order. Scroll sideways to see them all →
541–549
Plague of Justinian
Bubonic plague across the Byzantine Empire.
1347–1351
Black Death
Plague (Yersinia pestis) killed about a third of Europe.
1854
Broad Street cholera
John Snow's London outbreak (below), during the third cholera pandemic (1846–1860). The first of seven began in 1817.
1855–
Third plague pandemic
Began in Yunnan, China and spread around the world through port cities.
1889–1890
“Russian flu” pandemic
Spread around the world. Scientists do not know for certain which virus caused it.
1918–1920
1918 flu (“Spanish flu”)
An H1N1 flu virus; tens of millions of deaths worldwide.
1961–
Seventh cholera pandemic
The El Tor strain spread from Indonesia across Asia, Africa and Latin America, and is still going.
2002–2003
SARS
A new coronavirus (SARS-CoV) from China reached about 30 countries before isolation and quarantine contained it in 2003.
2009
H1N1 “swine flu” pandemic
A new flu virus mixing pig, bird and human flu genes (antigenic shift).
2014–2016
West African Ebola
The largest Ebola outbreak ever, mainly in Guinea, Liberia and Sierra Leone.
2014–2015
Flint, Michigan
Legionnaires' disease after the city switched its water source.
2019–
COVID-19 pandemic
Caused by the SARS-CoV-2 coronavirus.
"Father of epidemiology" on a test: most test writers mean John Snow (cholera, London, spot map). He's also called the father of field or modern epidemiology. Hippocrates is the common wrong answer: he was the first to tie disease to environment, so he's sometimes called the "first epidemiologist."
More Names Tests Ask About
Match the person to what they did.
Germs & medicine
Lady Mary Wortley Montagu1721
Brought variolation from Turkey to England, 75 years before Jenner.
Joseph Lister1867
Antiseptic surgery: cleaned wounds and tools with carbolic acid.
Hans Christian Gram1884
The Gram stain sorts bacteria by their cell walls.
Walter Reed1900
Showed that Aedes mosquitoes spread yellow fever.
Paul Ehrlich1910
Salvarsan, the first effective drug for syphilis: a “magic bullet.”
Stanley Prusiner1982
Discovered prions, infectious misfolded proteins.
Vaccines & eradication
Jonas Salk1955
Polio vaccine made from killed virus, given as a shot (IPV).
Albert Sabin1961
Polio vaccine made from live, weakened virus, given by mouth (OPV).
JE
John Enders1963
Grew measles virus in the lab; his team made the first measles vaccine.
D.A. Henderson1966–77
Led WHO’s smallpox eradication with surveillance and ring vaccination.
Studies & surveillance
Percivall Pott1775
Linked soot to cancer in chimney sweeps: the first job-related cancer.
Janet Lane-Claypon1912, 1926
Ran some of the first cohort and case-control studies.
Austin Bradford Hill1948
Designed the first randomized controlled trial (streptomycin for TB).
Alexander Langmuir1951
Founded the EIS; CDC’s first chief epidemiologist (from 1949).
Health, work & environment
Alice Hamilton1910s
Studied lead poisoning in factory workers; founded U.S. workplace medicine.
Joseph Goldberger1914–1920s
Showed pellagra came from a poor diet (no niacin), not germs.
Rachel Carson1962
Silent Spring exposed the harm done by the pesticide DDT.
CU
Carlo Urbani2003
WHO doctor who first spotted SARS in Hanoi; he died of it.
Portraits: Wikimedia Commons, public domain, except Stanley Prusiner (Christopher Michel), Janet Lane-Claypon (Wellcome Collection) and Austin Bradford Hill (unknown photographer), all CC BY 4.0. Hippocrates is shown as a sculpture; no portrait of John Graunt exists.
Landmark InvestigationJohn Snow and the Broad Street Pump
1 · The mystery
Summer 1854: cholera kills hundreds of people in London's Golden Square neighborhood in just days. Most doctors blamed miasma, “bad air” from rotting garbage. Germ theory hadn't been proven yet.
2 · Map it
Snow had no lab, so he used a map. He drew a dot for every death and an × for every water pump.
Figure 1.1. Snow's spot map of cholera deaths in the Golden Square area, London, 1854 (redrawn from the original). Each dot is a death; each × is a water pump.
3 · Follow the clues
The dots crowded around one pump on Broad Street. Even people who lived nearer other pumps had walked there, because they liked the taste of its water.
4 · A puzzle solved
A brewery right next to the pump had no deaths among its workers. Why? They drank the beer they made, not the pump water.
5 · Take action
Snow convinced officials to remove the pump's handle. The outbreak was already slowing, but it didn't come back. The pump handle became public health's most famous symbol.
6 · Count, divide, compare
Snow also compared two water companies: one took river water downstream of the city's sewage, one upstream. Homes on the downstream water had a cholera death rate more than 5 times higher.
Why it matters: step 6 is often called the first modern epidemiologic study: count the cases, divide by the people at risk, and compare the rates. That's the same logic you'll use on every Disease Detectives test.
Did Snow win the argument? Not in his lifetime. An 1855 government inquiry rejected his water theory. Miasma thinking lasted until germ theory (Pasteur in the 1860s, then Koch finding the cholera bacterium in 1883).
Why "shoe-leather" epidemiology? CDC's disease-detective training program, the Epidemic Intelligence Service (EIS), uses a shoe with a hole worn through the sole as its symbol. It's a nod to investigators who wear out their shoes walking door to door, tracking down cases and clues: exactly like Snow did in 1854.
After Snow, epidemiology spent most of the 1800s and early 1900s focused on acute infectious diseases. That changed in the mid-20th century, when studies linking smoking to lung cancer and the famous Framingham Heart Study turned epidemiology's tools toward chronic diseases like heart disease and cancer. In the 1960s–70s, epidemiologic methods helped eradicate smallpox worldwide, still one of public health's greatest victories. Since the early 2000s, epidemiologists have also had to watch for deliberately caused outbreaks (bioterrorism) alongside natural ones.
Tests often ask you to name a landmark study, say what it set out to find, and explain why it mattered. Know at least two of these cold:
1948–today · cohort
Framingham Heart Study
Objective
Follow thousands of residents of Framingham, Massachusetts for decades to find what causes heart disease.
Why it mattered
Identified the major cardiovascular risk factors (blood pressure, cholesterol, smoking) and made "risk factor" a household term.
1951–2001 · cohort
British Doctors' Study (Doll & Hill)
Objective
Track the smoking habits and causes of death of about 40,000 British doctors.
Why it mattered
Showed smoking causes lung cancer and other diseases, leading to anti-smoking policy worldwide.
1954 · field trial
Salk Polio Vaccine Trials
Objective
Test whether the Salk vaccine prevented polio. About 1.8 million schoolchildren took part: some got the vaccine, some got a placebo shot, and others were watched as controls.
Why it mattered
Proved the vaccine worked, launched mass polio vaccination and today's eradication effort, and set the model for large vaccine trials.
1964 · report
Surgeon General's Report on Smoking and Health
Objective
Review all the evidence on smoking and disease.
Why it mattered
Officially concluded that smoking causes lung cancer in men, and laid out criteria for judging whether something causes a disease.
1972 · community trials
North Karelia (Finland) & Stanford Three Communities
Objective
Test whether town-wide campaigns (ads, schools, healthier food) could cut heart disease risk.
Why it mattered
Showed whole communities can lower risks like smoking and high cholesterol.
1976–today · cohort
Nurses' Health Study
Objective
Follow over 100,000 female nurses to study how diet, lifestyle and hormones affect chronic disease in women.
Why it mattered
One of the largest studies of women's health; shaped advice on diet, smoking and hormone therapy.
1967–today · cohort
Whitehall Studies
Objective
Compare heart disease and death rates among British civil servants of different job grades.
Why it mattered
Showed lower job rank meant higher death rates, making the case for social determinants of health.
Current leaders (check every season): tests sometimes ask who runs the big public health agencies. As of fall 2026:
WHO Director-GeneralDr. Tedros Adhanom Ghebreyesus (since 2017; term runs to 2027)
CDC DirectorDr. Erica Schwartz (confirmed August 2026)
What made smallpox eradicable: not every disease can be wiped out, but smallpox had a rare combination of traits working in its favor: an effective, heat-stable vaccine; no animal reservoir (it only infected humans, so there was no hidden pool to reintroduce it); a distinctive, visible rash that made cases easy to spot and isolate; and no significant asymptomatic spread, so nearly every infected person could be found and contained. Rinderpest, a cattle disease, is the only other disease ever eradicated (2011).
✓ Check Yourself
Q1Which 19th-century investigator is considered the "father of field epidemiology," and what disease did he famously investigate?
John Snow, who traced an 1854 cholera outbreak in London to the contaminated Broad Street water pump.
Q2Name one landmark epidemiologic study, what it set out to find, and why it mattered.
Example: the Framingham Heart Study (1948 to today) followed Framingham, Massachusetts residents to find the causes of heart disease. It identified the major cardiovascular risk factors and made "risk factor" a core idea in chronic disease epidemiology.
Q3Put these in order, earliest first.
Drag to reorder (or use the arrows), then press Check.
