The 1928 Nobel Prize in Physiology or Medicine — Charles Nicolle

What You Will Learn in This Article

You will understand how a single observation – that a patient in a hospital would stop transmitting a disease as soon as they were undressed – led to the discovery of the true transmission route of typhus, and how this changed the principles of infectious disease control in the 20th century.

Taking Off Clothes Stops Transmission

In 1909, in a hospital in Tunis, Dr. Charles Nicolle was observing patients with typhus. This disease was extremely contagious, and when a patient arrived, it quickly spread to nurses, doctors, and other patients. But then, a surprising observation was repeated:

After a patient arrived in the emergency room, took off their clothes, bathed, and changed into hospital clothes before being moved to the ward, they would no longer infect anyone else. Even though the patient was still sick, with a fever and rash.

What did this mean? Nicolle’s conclusion was bold: “The infectious agent is on the patient’s clothes.” And the most likely candidate among the things living on those clothes? The louse.

This observation would break the 30-year-old mystery of typhus transmission. And it wasn’t just luck—it was the result of observational skills that didn’t ignore strange patterns in everyday life.

The Zeitgeist — The Peak of the Pasteur Network

In 1928, the world was on the eve of the Great Depression. The last few months of the Roaring Twenties were coming to an end, and the following year, the collapse of the New York Stock Exchange would plunge the world economy into turmoil. However, in that year, before the shadow of the Depression became clear, several symbolic events took place:

• Alexander Fleming’s observation of penicillin (September)—In the same year that Nicolle received the Nobel Prize, a chance observation in a London laboratory was about to fundamentally change the world of medicine.
• KLM’s first intercontinental scheduled flight (February)—The world began to shrink.
• The start of the first Soviet Five-Year Plan (October)—The beginning of Stalinist industrialization.
• Sony’s audio phone (first television broadcast)—The expansion of mass media.

From the perspective of medical history, this period was the peak of the Pasteur Institute’s global network. In addition to the Paris headquarters, branches in Tunis, Saigon, Dakar, and Shanghai served as centers for regional infectious disease research. This global network was the organization that first created a comprehensive map of infectious diseases around the world. And Nicolle’s Pasteur Institute in Tunis was one of the key nodes in that network.

When viewed in conjunction with Korean history, 1928 was a period of stabilization in the colonial administration, when Korean resistance was developing in various underground forms. There were activities by organizations such as the Sin’ganhoe, Geun’uhoe, and Joseoneo Yeonguhoe, but there was no real political freedom. While the European Pasteur network was comprehensively understanding the infectious diseases in each region, the map of infectious diseases in Korea was drawn only for the benefit of the colonial administration.

The Story of the Man — A French Bacteriologist in Tunis

Nicolle was born in Rouen, France, in 1866. After training at the Pasteur Institute in Paris, he was appointed director of the Pasteur Institute in Tunis in 1902. At the time, Tunis was a French protectorate, and the institute was a leading institution of French colonial medicine.

Nicolle’s arrival in Tunis was pivotal. At the time, Tunis was a hub for several infectious diseases:

• Typhus (chronic epidemic in the Mediterranean region)
• Malaria
• Tropical diseases (Leishmaniasis, etc.)

At the time, these diseases, which were difficult to access in university laboratories in Paris, were daily clinical problems in Tunis. Nicolle stayed there for over 20 years, unraveling the true transmission routes of each disease one by one.

He was a persistent observer. He spent more time observing patients in the hospital than cultivating bacteria in his own laboratory. In his Nobel Prize acceptance speech, he said: “I have learned more at the bedside of patients than I have by looking into petri dishes.”

This attitude made his discoveries possible.

Key Achievements — Defining the Vector

The Power of Observation

Nicolle’s approach to typhus was fundamentally different from that of other bacteriologists of the time.

The standard approach at the time (the era of Koch’s postulates):

1. Isolate bacteria from a patient
2. Pure culture
3. Inoculate another animal to reproduce the same disease
4. Confirm the cause

Nicolle’s approach:

1. Observe patients at various stages in the hospital
2. Discover at which stage the infectivity disappears
3. Identify what is removed at that stage
4. Confirm the vector candidate

This was an approach that prioritized epidemiological observation over bacterial isolation. And this approach worked perfectly for typhus. If the infectivity disappeared when the patient was moved to the ward and took off their clothes and bathed, then something on the clothes was the vector.

A CS analogy fits naturally here. This is similar to packet tracing to discover a man-in-the-middle (MITM) attack node. When there is strange data distortion in software communication, we capture packets at each node to determine at which point the distortion is inserted. Nicolle traced the “infectivity” signal at each stage of the hospital process, and localized the vector by identifying the point at which that signal disappeared.

However, this analogy breaks down here. Software tracing leaves clear logs, but Nicolle’s observations were based on the patient’s case and the statistics of infected staff. This data is noisy, and it is difficult to distinguish between correlation and causation. Nevertheless, he was able to accurately identify the vector because he repeatedly observed consistent patterns in multiple cases.

The Louse Experiment

To verify his hypothesis (that lice on clothing were the vector), Nicolle designed an experiment. He injected the blood of a typhus patient into a chimpanzee, infecting it, and then allowed lice from the chimpanzee to feed on a healthy chimpanzee. After that, when the lice were placed on a healthy chimpanzee, the chimpanzee contracted typhus.

This experiment was decisive. It was empirically proven that lice were the vector of typhus, and the microorganism within them was later identified and named Rickettsia prowazekii.

The clinical impact of this discovery was immediate. The principles of typhus prevention were completely changed: lice control is more important than patient isolation. Disinfection of clothing, bathing, and louse control. This is the archetype of the standard protocols we use today for typhus control.

The Discovery of Silent Infection

Nicolle’s second key observation was the existence of silent infection. He observed that people who had contact with typhus patients but showed no symptoms themselves could later transmit the disease to others. This observation is the archetype of today’s concept of asymptomatic carriers.

Why is this concept important? Until then, infectious disease control had focused on isolating sick people. After the concept of asymptomatic carriers, the response became much more complex: even if they are not sick, they must be tested, isolated, and contact traced. This is one of the fundamental principles of today’s COVID-19 response. The observation made 100 years ago by Nicolle created a framework that is still valid today.

To summarize with a CS analogy, asymptomatic carriers are like background processes that do not appear in the logs. Processes that are not visible in system state monitoring but are actually actively transmitting data. To catch such processes, we must monitor the network traffic itself. Nicolle established this principle for the first time in infectious disease control.

Why It Matters

Nicolle’s Nobel Prize was for establishing the principle that “vector-borne disease control must address the vector.” This principle has led to several successful responses:

• Malaria control—Prioritize mosquito control. DDT and insecticide-treated nets are applications of this principle.
• Yellow fever control—Control of Aedes aegypti mosquitoes.
• Dengue fever and Zika—Vector mosquito control and habitat management.
• Lyme disease—Tick control and prevention.

Another major legacy is the principle that “clinical observation itself is crucial data.” Nicolle made his discoveries by observing patients in the hospital rather than culturing bacteria in the laboratory. This approach has evolved into a separate field of study today, called clinical epidemiology. The fact that large-scale observational studies produce knowledge that complements laboratory research—this is one of the two pillars of infectious disease control today.

There is a lesson for us. It is to “observe what changes at each stage of the process.” Nicolle knew that patients went through several stages in the hospital, and he precisely localized the stage at which the infectivity disappeared. This is exactly the same logic as we use in software debugging, where we reproduce the issue and isolate each stage to localize the cause. The precision of observation determines the precision of the discovery.

Even as you read this sentence, vector-borne disease control is ongoing in various parts of the world. One of the conceptual roots of that response began 100 years ago in the emergency room of a hospital in Tunis.

Concluding the 20-Part Journey

This 20-part journey, which began with Koch’s thyroid surgery in 1909, concludes with Nicolle’s discovery of the vector in 1928. During that 20 years, the world of medicine changed dramatically:

• Surgery became a precise science (1909, Koch; 1912, Carrel).
• The chemistry within cells was first documented (1910, Kossel).
• The precise optics and balance system of the eye and ear were understood (1911, Gullstrand; 1914, Barany).
• The paradox of immunity and the double-layer structure were elucidated (1913, Richet; 1919, Bordet).
• The active regulation of microcirculation was confirmed (1920, Krogh).
• Energy accounting and insulin were established (1922, Hill and Meyerhof; 1923, Banting and Macleod).
• The electrical signals of the heart were recorded on paper (1924, Einthoven).
• Psychiatry received its first Nobel Prize (1927, Wagner-Jauregg).
• The principles of vector-borne disease were established (1928, Nicolle).

Although there were no Nobel Prizes in the six years (1915, 1916, 1917, 1918, 1921, 1925), we have seen that the fundamental infrastructure of 20th-century medicine was built during that downtime.

The fact that this short period between the two World Wars was one of the most important periods in shaping today’s medicine—that is the true theme of these 20 articles.

Nicolle’s Vector Tracing Summary: He observed patients at each stage of the hospital, localized the stage where infectivity disappeared, and identified the vector (clothing, lice) by identifying what was removed at that stage. This approach became the standard for vector-borne disease control.

→ Experience it with coding: DevBench — Process Tracing and Localization → Learn about CS concepts: DryBench — Vector Node Discovery and Log Tracing