Carlos Juan Finlay and Yellow Fever

Summary

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Podcast Summary: Stuff You Missed in History Class

Episode: Carlos Juan Finlay and Yellow Fever
Hosts: Tracy V. Wilson & Holly Fry
Date: May 25, 2026
Podcast by: iHeartPodcasts

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Episode Overview

This episode dives deep into the life and legacy of Dr. Carlos Juan Finlay, a Cuban physician whose groundbreaking hypothesis identified mosquitoes as the vector for yellow fever—years before scientific consensus caught up. While Finlay’s work set the foundation for crucial advancements in epidemiology, especially the experiments later made famous by U.S. Army doctor Walter Reed, Finlay often faced skepticism and was overlooked in favor of others. Holly and Tracy highlight both his scientific achievements and the historical context of his work, exploring why his essential contributions were ignored for decades.

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Key Discussion Points & Insights

1. Finlay’s Background and Early Life

• Birth and Family Heritage
  • Born December 3, 1833, in Camagüey, Cuba.
  • Son of a French-Trinidadian mother and a Scottish father, both immigrants to Cuba.

    "Like to one other great Antillean, Alexander Hamilton, he was born of two great races, the Scotch and the French." — Tracy quoting Dr. Juan Gutierrez (04:14)

• Education and Challenges
  • Educated at home, then sent to France at 11.
  • Suffered from chorea—a movement disorder—affecting his speech, which led some to misjudge his intellect.
  • Education interrupted by illness and political unrest (the Revolution of 1848, typhoid fever).
• Linguistic Prowess & Medical Training
  • Fluent in Spanish, English, German, French, and skilled in Greek and Latin.
  • Denied entry to medical school in Havana, attended Jefferson Medical College in Philadelphia (graduated 1855).

2. Early Medical Career and Focus on Public Health

• Practiced general medicine, ophthalmology, and neurology in Cuba, France, and Peru.
• Married Adela (from Trinidad); had three children.
• Swiftly turned focus to public health crises in Cuba, notably yellow fever.

3. The Burden of Yellow Fever in Cuba

• Yellow fever described as a viral hemorrhagic disease, with devastating outbreaks, especially among non-immune populations like Spanish soldiers.
  • Up to 50% fatality in serious cases ([09:23]).
• The disease became endemic in Cuba due to the transatlantic slave trade and thriving Aedes aegypti mosquitoes.

4. Finlay’s Hypothesis: Mosquitoes as Disease Vectors

• Recognized patterns in outbreaks, considered environmental and biological transmission possibilities.

• By 1881, posited that mosquitoes, specifically Aedes aegypti, spread yellow fever.

  • Introduced at the International Sanitary Conference in Washington, D.C. ([20:08]).

    "He said that he believed an intermediate agent played a role in yellow fever transmission. He said that he was not yet ready to say what that intermediate agent was, but that he was working on a paper about it." — Holly (20:23)

• First substantial paper:

  "The Mosquito Hypothetically Considered as the Transmitting Agent of Yellow Fever" presented in Havana (22:02).

• Detailed logic and experimental work, including controlled mosquito-to-human exposures, though limited by scientific means of the time (no knowledge of viruses, could not culture the agent, [21:35]).

  • Finlay’s own summary of transmission requirements ([23:19]):

    “1. The existence of a yellow fever patient into whose capillaries the mosquito is able to drive its sting... 2. That the life of the mosquito be spared... 3. The coincidence that some of the persons whom the same mosquito happens to bite... shall be susceptible..."

5. Scientific Rejection and Ridicule

• His hypothesis ran counter to prevailing wisdom (fomite theory) and upended public health practices of aggressive cleaning and disinfection ([25:47]).
• Ostracized in the Cuban research community; dubbed "the Mosquito Man" ([26:33]).
• Professional isolation led to emotional hardship for Finlay, with support only from a few, notably his wife and Dr. Claudio Delgado ([27:50]).

6. Persistent Research and Accumulating Evidence

• Performed 102 experiments, primarily using recent arrivals to Cuba as volunteers; his aim was to create immunity, not necessarily full-blown disease ([28:45]).
• Documented long-term outcomes (over three years) of 67 volunteers, showing successful "acclimatization" to yellow fever ([30:28]):

  “92.2% of these test subjects were acclimated to yellow fever by being bitten by a mosquito in this experiment having at most very mild symptoms.” — Tracy (31:24)

7. The Walter Reed Commission and U.S. Recognition

• By 1900, U.S. Army Yellow Fever Board (including Walter Reed) visited Finlay, used his mosquitoes and methods.
• Confirmed mosquito transmission, announced by Reed on October 23, 1900 ([40:18]).
  • Reed acknowledged Finlay:

    "It was Finlay's theory, and he deserves much for having suggested it." — Reed quoted by Holly (41:03)

• Despite this:
  • The U.S. focus on Reed and the Army's role in controlling yellow fever overshadowed Finlay ([41:44]-[42:36]).
  • Recognition more prominent in Cuba and Europe; Finlay became chief sanitary officer of Cuba ([42:36]).

8. Legacy and Later Years

• Led successful mosquito control campaigns in Cuba, contributing to yellow fever's eradication in many regions ([43:22]).
• Researched and implemented programs to reduce neonatal tetanus ([43:55]).
• Retired in 1909; received some late recognition, but never awarded a Nobel, though nominated seven times ([44:58]).
• Died August 20, 1915, after publishing 40 articles on yellow fever and many on other diseases.

9. Modern Relevance

• Finlay’s insight underpins prevention methods for yellow fever and other mosquito-borne diseases to this day.
• Yellow fever remains present in parts of Africa and Latin America; vaccination and mosquito control are critical ([46:25]-[46:55]).

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Notable Quotes & Memorable Moments

• On National Heritage and Character:

  “From the Scotch he inherited the intensity... from the French he received his characteristic amiability and courtesy together with a lively imagination and the love of glory..."
  — Dr. Juan Gutierrez, as read by Holly (04:37)

• On Scientific Bias:

  “Finlay's conclusions were not just dismissed, they were ridiculed. People started calling him the ‘Mosquito Man’.”
  — Tracy (26:33)

• Finlay’s Experimental Philosophy:

  “I understand but too well that nothing less than an absolutely incontrovertible demonstration will be required before the generality of my colleagues accept a theory so entirely at variance with the ideas which have, until now prevailed about yellow fever.”
  — Finlay, as read by Holly (24:40)

• On Having His Work Recognized:

  “But it has been enough to break anyone's heart to see himself so utterly ignored while the world has been singing the praises of the men upon whom he forced his ideas.”
  — Tracy (44:48)

• Finlay’s Broader Contribution:

  “He was nominated for the Nobel Prize in physiology or medicine seven times, but he was never awarded it.”
  — Tracy (44:58)

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Important Timestamps

• Finlay’s early life, background, and education: 02:25–07:58
• Focus on yellow fever and the historic burden in Cuba: 09:23–13:36
• Finlay’s hypothesis and presentation to scientific community: 20:08–25:03
• Scientific rejection and community backlash: 26:33–27:22
• Experimental work and findings: 28:15–31:24
• U.S. Army involvement; Walter Reed’s confirmation: 37:48–41:44
• Recognition, legacy in Cuba, and modern implications: 42:36–47:47

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Conclusion

Carlos Juan Finlay was ahead of his time—his work on yellow fever transmission was methodical, inspired, and, for many years, marginalized. The episode not only re-centers Finlay’s role in public health history but also highlights the social and scientific obstacles that hinder groundbreaking discoveries. By the end, listeners are left with a nuanced appreciation for Finlay’s perseverance and the ripple effects of his work in today’s fight against mosquito-borne diseases.

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For further reading and show notes, visit the podcast website.

Transcript

[Tracy V. Wilson]

This is an iHeart podcast guaranteed human

[Holly Fry]

living with a rare autoimmune condition brings uncertainty, but it can also create community. In season six of Untold Life with a Severe Autoimmune Condition, they go beyond MG and cidp as host Martine Hackett welcomes stories from other conditions like myositis and IgAN into the conversation. Untold Stories is produced by Ruby Studio in partnership with Argenics. Listen to Untold Stories Life with a Severe Autoimmune condition on the iHeartRadio app, podcasts, or wherever you get your podcasts. Wouldn't it be great to never buy gas again? EVs are as easy to charge as your phone, and they are a perfect addition to your everyday life. Most people are only driving about 40 miles a day, and most EVs can handle 200 to 400 miles of range on a charge. And there are hundreds of EV models available today, so there's something perfect for every lifestyle and budget. I drive an ev. I've had it for a couple of years. It's my favorite car I've ever owned. It is so fun to drive. The pickup is incredible. It's super agile and it is easy to maintain. The way forward is electric. Learn [e-mail] Work can be a little weird.

[Tracy V. Wilson]

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[Holly Fry]

Stuff youf Missed in History Class, a production of iHeartradio.

[Tracy V. Wilson]

Hello and welcome to the podcast. I'm Tracy V. Wilson.

[Holly Fry]

And I'm Holly Fry.

[Tracy V. Wilson]

And way back in 2014 we did an episode on Walter Reed which we reran as a Saturday classic maybe 3ish years ago. Walter Reed was a US army physician who was most known for his work on illnesses that were really affecting soldiers in the Caribbean, especially yellow fever. In that episode we talked about how Reed's work was really based on that of a Cuban doctor named Carlos Juan Finlay. I'm going to take a pronunciation moment here because I think a lot of people in English speaking countries pronounce that name, which is spelled F I, N L A Y, as Finley. But everything I found from an institute named after him and some things from Spanish speakers in Cuba pronounced it more like Finlay. So that's what we are going with. So Finlay had already figured out a lot of what Reed and his team confirmed and then were pretty much given credit for. I've always wanted to talk more about Finlay and now we are finally.

[Holly Fry]

Juan Carlos Finlay was born on December 3, 1833. He was born in Camague in central Cuba, which was at the time known as Santa Maria del Puerto del Principe. He went by Carlos and later on in his life started using J as his middle initial to differentiate from his son Carlos, Carlos Eduardo Finlay, who became an accomplished doctor and professor of medicine in his own right.

[Tracy V. Wilson]

Carlos's parents were both immigrants to Cuba. His mother, Elizabeth Debar, known as Eliza, was a French woman from Trinidad. His father, Edward Finlay, was from Scotland. In the words of a biographical sketch by Cuban physician and yellow fever specialist Dr. Juan Gutierrez, which was published in 1912, quote, unquote, like to one other great Antillean, Alexander Hamilton, he was born of two great races, the Scotch and the French. A quote I included in this episode because it made me laugh so hard when I read it for the first time.

[Holly Fry]

Gutierrez also had this to say about Finlay's personality and what his parents nationalities had to do with it. Quote from the Scotch he inherited the intensity and the ardor in the pursuit of an objective, together with the logic, discipline and the inclination to theorize upon and insistently to discuss abstruse subjects without losing, however, the golden thread of their practical application. From the French he received his characteristic amiability and courtesy together with a lively imagination and the love of glory, which though not apparent on the surface, must have spurred the Scotchman in his noble ambition. I feel like this is attributing a lot of stuff to his behavior that really we have no scientific basis for. But according to Guterres, that was tempered by, quote, the most exquisite Modesty, a virtue which I am pleased to think was fostered in the Creole atmosphere of the time, together with a great love for the land of his birth.

[Tracy V. Wilson]

Yeah, I really feel like that quote is a combination of a description of his personality and an example of how much people thought a national origin could affect a person's character. So at first, when Carlos was a child, he was educated at home, and when he was 11, his parents sent him to a school in France. His father was a doctor and wanted him to have access to a prestigious European education. But that education wound up having a lot of interruptions. First, Carlos got sick. Most accounts describe this as chorea, possibly Sydenham chorea, which is a movement disorder that can develop in children after they've had an illness like strep throat or scarlet fever. This affected his speech, and after Carlos got home, his father developed a regimen to try to help him recover. And it did help. For the rest of his life, Carlos spoke slowly and his speech could sound slurred, which sometimes affected people's perceptions of his intent intelligence. Gutierrez also suggested that the speech disorder came from Carlos's brain and might have been connected to his seeming perpetually absent minded.

[Holly Fry]

Carlos went back to France when he was 15, but before long he had to leave again due to the Revolution of 1848, which overthrew France's constitutional monarchy. Carlos went to London for a while and then spent a year studying in Germany before going back to France and and enrolling in college in rouen. Then in 1851, he faced yet another interruption when he contracted typhoid fever and had to once again go back home to Cuba to recover.

[Tracy V. Wilson]

By this point, Finlay was fluent in Spanish, English, German and French, and he knew enough classical Latin and Greek to translate works in those languages into Spanish for fun. His coursework in Europe was equivalent to a Bachelor of Arts, and he had reached a point in his education that once he recovered, the next step would be medical school. But the medical school at the University of Havana would not accept these credentials.

[Holly Fry]

So Finlay went to Philadelphia to attend Jefferson Medical College, earning his medical degree. On March 10, 1855, his professors and mentors encouraged him to go to New York and work with the Spanish speaking immigrant community there. But he wanted to go back to Cuba. He did, and Spanish authorities validated his medical degree and approved him to practice medicine there in 1857.

[Tracy V. Wilson]

Finlay didn't establish a permanent practice in Cuba right away. He went back to France for a while to continue his education in neurology and ophthalmology. He and his father also went to Peru together, and they practiced medicine there. On October 16, 1865, Carlos married a woman named Adela, who was from Trinidad. They would go on to have three children together. Carlos Eduardo in 1868, Jorge Enrique in 1870, and Jose Maria Francisco in 1876.

[Holly Fry]

In 1869, the family went to Trinidad to visit Adela's family. According to Guatera's biographical sketch, in 1875, Carlos also went to New York, quote, in search of professional advice for Mrs. Finlay, which suggests that she was having a medical issue and that he wanted to consult a specialist. But Gutierrez doesn't suggest what that issue may have been.

[Tracy V. Wilson]

At the beginning of his medical career, including while he was practicing outside of Cuba, Finlay focused on general medicine along with ophthalmology and eye surgery. But by the 1860s, he was focusing more on diseases that were public health issues in Cuba, including yellow fever, which is a viral hemorrhagic fever. Most people who contract yellow fever have symptoms like fever, chills, body aches, nausea, vomiting, and weakness, and they recover within three or four days. But about 15% of people who contract yellow fever develop a serious illness that has a much higher fever and organ damage, jaundice, hemorrhaging, and black vomit caused by that hemorrhaging and organ destruction. Still today, as many as 50% of people who develop this more serious version of the disease die within seven to 10 days.

[Holly Fry]

Today, we know that yellow fever is spread by mosquitoes, especially Aedes aegypti, which thrives in warm climates and is native to Africa. These mosquitoes were introduced to the Caribbean and the Americas through the transatlantic slave trade, and the first reports of yellow fever in the Americas were in the 17th century century. The disease soon became endemic in tropical areas that had a large enough population for sustained transmission. It also caused huge, devastating outbreaks in places outside the tropics, as mosquitoes and sick passengers arrived aboard ships. In the United States, there were frequent outbreaks in the south, but they could happen in the north as well. For example, about 10% of the people living in Philadelphia died in the yellow fever outbreak in 1793.

[Tracy V. Wilson]

Yellow fever also became a particular problem for Spanish colonial authorities and the Spanish military in Cuba. Spain had claimed Cuba as its territory in 1492 and started establishing settlements there in the 1500s. Cuba's indigenous population included multiple Arawakan speaking peoples, and they faced displacement, introduced diseases, violence, and genocide. Indigenous people and enslaved Africans rose up against the Spanish in Cuba for decades, and in 1868 an anti colonial uprising began that came to be known as the Ten Years War and this war was interconnected with the movement to abolish slavery.

[Holly Fry]

Large numbers of Spanish soldiers were sent to Cuba to put down this uprising and they were vulnerable not just to yellow fever, but to a range of other tropical diseases that their immune systems had no experience with. They were also housed in close quarters, making it easy for infected mosquitoes to bite multiple people. This contributed to the spread of other diseases, including malaria, which is also spread by mosquitoes, and typhus, which is spread by fleas and lice.

[Tracy V. Wilson]

Serious illnesses became an enormous problem for the Spanish military, with death rates that were much, much higher among soldiers than they were among the civilian Cuban pop. That continued to be true after the Ten Years War ended in 1878, including during the Cuban War of Independence that started in 1895. More than 90% of the deaths among Spanish troops between 1895 and 1898 were due to disease, not combat injuries, and more than a third of those deaths were from yellow fever.

[Holly Fry]

Maximo Gomez, yes, leader of the Cuban Liberation army during the Ten Years War and the Cuban War of Independence, described June, July and August as his best generals. Those were the months when many of these diseases peaked and the months when mosquitoes were most active, but at the time they didn't know that mosquitoes were spreading the illness. The person who figured out the mosquito part was Carlos Juan Finlay.

[Tracy V. Wilson]

We will talk about that after a sponsor break.

[Holly Fry]

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[Tracy V. Wilson]

The focus in today's episode is Yellow Fever, but in addition to his postgraduate training in ophthalmology, Carlos Juan Finlay also studied and wrote on a range of other illnesses that were affecting people in Cuba. One was cholera. In 1867, he suggested that the source of a cholera outbreak was sewage contamination of a water supply. Over the course of his work, he also published papers on tuberculosis, tetanus, leprosy, nutritional diseases like beriberi, and parasitic diseases like trichinosis and filariasis. He was writing about yellow fever. By 1865, Finlay developed a thorough knowledge

[Holly Fry]

of the late 19th century's medical understanding of yellow fever. He also studied the air in Havana, measuring its alkalinity and cross referencing that with the seasons, the climate, and public health. He noticed that the air seemed to be more alkaline in times when yellow fever outbreaks peaked, and he thought there might be some kind of connection there.

[Tracy V. Wilson]

In 1879, after the end of the Ten Years War, the United States sent a commission of doctors to Cuba to study yellow fever in the US Interest in the disease was primarily connected to those unpredictable and horrifying outbreaks that struck American cities. A huge outbreak had struck more than a hundred cities and towns in the southern US the year before.

[Holly Fry]

Because of his reputation and his previous work on yellow fever, Finlay was appointed to work with the U.S. commission. They did not pinpoint the cause of yellow fever or correctly identify how it was spread, but this work did connect Finlay to US army physician and bacteriologist George Miller Sternberg, the commission's microscopist. Finlay and Sternberg became friends, and Sternberg shared his collection of slides containing blood and tissue samples from yellow fever patients with Finlay.

[Tracy V. Wilson]

The commission's report concluded that the infectious agent that caused yellow fever had to be replicating somewhere outside of human bodies before it infected them. I could not get my hands on this actual report, but that is how it was characterized. In other writing about it, Finley had also learned about a type of corn rust that had to incubate in barberry bushes before it could infect the corn. That combined with his microscopic study of Sternberg's blood and tissue samples and what the blood cells and vessels looked like in those samples, he started to wonder if yellow fever could be introduced into the body through the bite of an insect.

[Holly Fry]

By 1881, Finley was confident that yellow fever was being spread by mosquitoes, specifically the females of the species known as Aedes aegypti. Today, it has had multiple other scientific names at various points in the past, so if you do additional reading, you may see that species name differently. But on February 18th of 1881, he presented at the International Sanitary Conference in Washington, D.C. and he said that he believed an intermediate agent played a role in yellow fever transmission. He said that he was not yet ready to say what that intermediate agent was, but that he was working on a paper about it.

[Tracy V. Wilson]

This presentation was not received very well. He had been selected to attend this conference without a lot of notice, so he hadn't had time to really do a lot of experiments to verify what he had concluded based on his observations so far. Even though he was sure that the mosquito was the vector in question, he did not want to make that announcement without evidence to support it. Nobody from the audience asked him any questions about his presentation. But apparently somebody did tell him that he needed to follow Robert Koch's postulates, including isolating the organism in question, culturing it, and confirming that it caused disease in a healthy subject.

[Holly Fry]

This would have been impossible at the time. Koch's postulates were developed through study of bacterial illnesses like anthrax and tuberculosis, which could be filtered, cultured and observed through a microbe microscope. Yellow fever is caused by a virus, and viruses could not be filtered, cultured or seen using the technologies that were in existence at the time. People did not yet know that viruses existed.

[Tracy V. Wilson]

On August 14, 1881, Finlay delivered a paper titled the Mosquito Hypothetically Considered as the Transmitting Agent of Yellow Fever before the Havana Academy of Sciences. In it, he referenced Sternberg's tissue samples, quote showing what to me appeared to be a most striking feature, namely that the red blood globules are discharged unbroken in the hemorrhages of yellow fever. This fact, taken in connection with the circumstance that those hemorrhages are often unattended with any perceptible break in the blood vessels, while on the other hand, they constitute a most, most essential clinical symptom of the disease, led me to infer that the principal lesion of yellow fever should be sought for in the vascular endothelium. The disease is transmissible. It attacks but once the same person and always presents in its phenomena a regular order comparable with that observed in the eruptive fevers. All of which circumstances suggested to my mind the hypothesis that yellow fever should be considered as a sort of eruptive fever in which the seat of the eruption is the vascular endothelium.

[Holly Fry]

He walked through what was needed for yellow fever to be transmitted. Quote 1. The existence of a yellow fever patient into whose capillaries the mosquito is able to drive its sting and to impregnate it with the virulent particles at an appropriate stage of the disease. 2. That the life of the mosquito be spared after its bite upon the patient until it has a chance of biting the person in whom the disease is to be reproduced. 3. The coincidence that some of the persons whom the same mosquito happens to bite thereafter shall be susceptible of contracting the disease.

[Tracy V. Wilson]

He also explained the mosquito's physiology and behavior and how they facilitated the spread of yellow fever. He described the experiments that he had conducted in which he allowed a mosquito to bite a yellow fever patient and then later bite someone who had never had yellow fever. This seemed to lead to mild cases of yellow fever, and several of his test subjects were diagnosed with, quote, abortive yellow fever. But most of his test subjects didn't develop any kind of symptoms. Quote Barring my first three inoculated men, no other case of confirmed or abortive yellow fever has occurred among the 20 non immunes whom I have had under observation.

[Holly Fry]

He also very clearly understood that his conclusions would be controversial. Wrote quote, I understand but too well that nothing less than an absolutely incontrovertible demonstration will be required before the generality of my colleagues accept a theory so entirely at variance with the ideas which have, until now prevailed about yellow fever.

[Tracy V. Wilson]

The prevailing idea about yellow fever at this point was that it was spread through fomites, I.e. inanimate objects or materials that could carry infectious agents. And when it came to yellow fever, especially severe hemorrhagic cases of yellow fever, this idea made so much sense. Since yellow fever is a hemorrhagic disease, patients bled and they vomited their linens. The medical equipment and the rooms where they were being treated became soiled, and the nature of that contamination was just viscerally horrifying. So a big part of attempts to control the spread of yellow fever was relentless aggressive cleaning and disinfection of those spaces.

[Holly Fry]

So Finlay's hypothesis about mosquitoes wasn't just going against the prevailing medical knowledge about yellow fever. If he was correct, it also meant that the one thing people felt like they could do to control yellow fever was wrong. And all the time and money and effort that had been spent on disinfecting linens and scrubbing hospital walls and floors had been essentially useless in 1881. There was also only one other disease that had been identified as being spread by insects, A parasitic infection called filariasis. Although the transmission of that was not fully understood until 1901, people just did not think of insect borne diseases as a real possibility.

[Tracy V. Wilson]

So Finlay's conclusions were not just dismissed, they were Ridiculed people started calling him the Mosquito Man. Other researchers in Cuba excluded him from their work. That included Juan Santos Fernandez, who established and funded a histobacteriological laboratory and institute of rabies vaccination in 1885. In addition to dismissing Finlay's work, Santos Fernandez hired Diego Tamayo, who was another vocal critic of Finlay's, to head up that institute's yellow fever research. This dismissal and derision continued after Finlay did more research and published yellow fever, its transmission by means of the Culex mosquito, in the American Journal of the Medical Sciences in 1886.

[Holly Fry]

This was obviously both personally and professionally crushing. It shook Finlay's faith in the broader scientific and medical community. It was true that his conclusions had come from his observations and limited experiments on volunteers, not through rigorous controlled studies or following Koch's postulates. But he was also confident that his conclusions were correct and that they were worth examining further.

[Tracy V. Wilson]

Finlay's wife was a big source of support. Another was Claudio Delgado, a doctor from Spain who was Finlay's friend and colleague and continued to work with him through all of this. They lobbied for the establishment of another bacteriological research facility dedicated specifically to finding the cause of yellow fever. Again, viruses still had not been discovered yet, which is why their focus was still on bacteria.

[Holly Fry]

Their efforts to establish a new research center were unsuccessful. But Finlay continued to gather supporting evidence for his hypothesis through 102 experiments on human volunteers. Most of them were new arrivals to Cuba, including soldiers and Catholic clergy. He had the cooperation of Jesuit and Carmelite fathers working in Cuba and of Captain General Ramon Blanco, who was a Brigadier general and colonial administrator.

[Tracy V. Wilson]

A lot of writing about this research, including the way we described it in our episode on Walter Reed, Mrs. Something really important. Finlay is characterized as not understanding that it takes roughly two weeks for the yellow fever virus to replicate in a mosquito's body before it can cause serious illness. And that's why most of his experiments did not result in patients who had full blown yellow fever. This is presented as a reason why people were not taking him seriously. He was waiting only long enough for the mosquito to digest the infected blood it had consumed than to be hungry again. This only took about four days. So his experimental subjects typically did not get very sick if they showed any symptoms at all. But he was not trying to give people full blown yellow fever. He was using these mosquito bites as an inoculation, much like intentionally exposing someone to cowpox, which is a mild disease, to make them immune to Smallpox and

[Holly Fry]

his test subjects did seem to have resistance to yellow fever after being bitten. In 1891, Finlay published Inoculations for yellow fever by means of contaminated mosquitoes in the American Journal of the Medical Sciences. In this paper, he rebutted some of the criticism of his earlier work, and he also presented the results of a study of 67 volunteers who were monitored for three or more years after being bitten by a mosquito that was infected with yellow fever. During that three year period, they lived in parts of central Havana where there were frequent yellow fever outbreaks.

[Tracy V. Wilson]

This observation was still ongoing, so 15 of them hadn't gotten to that three year mark yet. But they also had not had any indication of contracting yellow fever. 12 had developed a fever within 25 days of being bitten by the mosquito, and they either had or had not had albumin in their urine, which is a sign of yellow fever. Twelve of them had no symptoms at all after being bitten and also no other yellow fever symptoms in the three years since then. 24 of them had no symptoms after being bitten and then had a mild fever sometime in the three years afterward, but no other sign of yellow fever beyond that. Three had no symptoms after being bitten and then later got yellow fever but recovered, and then one had no symptoms after being bitten, but then later on got yellow fever and died.

[Holly Fry]

Outsiders who came to Cuba were described as acclimated once they no longer seemed susceptible to the tropical diseases that were endemic there. Usually that happened after repeated illnesses, at least some of them serious. By Finlay's calculations, 92.2% of these test subjects were acclimated to yellow fever by being bitten by a mosquito in this experiment having at most very mild symptoms. That acclimation was the goal, not a full blown case of a potentially deadly disease.

[Tracy V. Wilson]

We'll talk about how Walter Reed wound up being given a lot of the credit for the discovery that mosquitoes spread yellow fever after a sponsor break.

[Holly Fry]

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[Tracy V. Wilson]

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[Holly Fry]

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[Tracy V. Wilson]

In 1893, Carlos Juan Finlay and Claudio Delgado started started collaborating with some of the researchers from Juan Santos Fernandez's institute. At that point, Diego Tamayo had resigned and while Santos Fernandez was not a believer in Finlay's ideas, there were less objections to working with him. That continued until 1895 with the start of the Cuban War of Independence. Medical and scientific research really struggled during the war. In addition to the typical risks and hardships of war, a lot of Cuban doctors and researchers started leaving for the United States.

[Holly Fry]

The U.S. became directly involved in this war between Cuba and Spain in 1898, after Congress issued resolutions supporting Cuban independence and demanded a withdrawal of Spanish troops, Spain declared war on the US which then declared war on Spain. And from the US Point of view, this part of it is known as the Spanish American War. Finlay was in Tampa, Florida when the US declared war on Spain and he traveled to Washington, D.C. to volunteer his service as a surgeon. He was sent back to Cuba aboard a hospital ship. He was 64 at this point.

[Tracy V. Wilson]

The Spanish American War ended with a treaty signed in Paris on December 10, 1898. Under this treaty, Spain ceded the islands of Guam and Puerto Rico to the United states and the US purchased the Philippines from Spain for $20 million. This treaty also guaranteed Cuba's independence, with the United States temporarily occupying Cuba and establishing a military government. The US Occupation lasted from the end of the war until Cuba became formally independent in 1902.

[Holly Fry]

George Miller Sternberg, the microscopist who had become Finlay's friend and colleague back in 1879, was now the Surgeon General of the Army. And the U.S. army faced the exact same issues with yellow fever and other tropical diseases as the Spanish army had. US Soldiers arrived in Cuba and quickly got sick with one disease after another, with diseases becoming a much bigger issue for soldiers than combat. The same was true on the other islands that the US had acquired from Spain and was now occupying. So there was a big focus on finding out how to prevent and treat yellow fever and other tropical diseases.

[Tracy V. Wilson]

By this point, there was a little less resistance to the idea that a disease could be spread through these kinds of bites. Ticks, which are arachnids, were identified as the vector In Texas cattle fever in 1890. Mosquitoes were identified as transmitting malaria in 1897. So when the US Army Yellow Fever Board visited Cuba in 1900, mosquitoes did not seem quite as far fetched as a vector of the disease. This was not the first commission the United States sent to Cuba for this kind of research. We talked about the one in 1879, and then there had been other ones in between. But this is the one that army physician Walter Reed was part of, and it's so associated with him that sometimes it is called the Reed Commission.

[Holly Fry]

Reed and his team eventually visited Finlay. They used mosquito eggs that he had collected and did experiments that were very similar to his own. Putting a mosquito in a test tube and then putting the mouth of that tube against the skin of someone who had yellow fever. Once the mosquito fed on that person, they would wait until it had digested its meal and then have it bite someone else. I will confess that this all puts a cartoon in my head. The idea of waiting for a mosquito to digest things like, did you enjoy your soup, sir? A member of this commission named James Carroll participated in one of these experiments, contracted yellow fever, and recovered another. Jesse Lazear was apparently bitten by a mosquito in the lab. Not part of this controlled experiment, just a mosquito that was flying around in a building that also housed yellow fever patients. He contracted yellow fever and unfortunately died.

[Tracy V. Wilson]

Based on the commission's research in Cuba, Reed announced that mosquitoes had been conclusively determined to be the vector for yellow fever on October 23, 1900. Reid's commission is sometimes also credited with figuring out the amount of time required for a mosquito to be able to infect someone with a serious case of yellow fever called the extrinsic incubation period. That, however, was discovered by Henry Rose Carter in experiments carried out in Mississippi in 1898. Carter did not publish this work until 1900, though, and one of the sources used in this episode also said that Finlay already understood this part of it as well.

[Holly Fry]

When Reid announced and wrote about this work, he made some references to Finlay, including at one point saying, quote, it was Finlay's theory, and he deserves much for having suggested it. William Crawford Gorgas, who would later become Surgeon General of the US army and was in charge of sanitation during the building of the Panama Canal, called Finlay's reasoning behind identifying the mosquito as the best piece of logical reasoning that can be found in medicine anywhere, and also described the US as owing a great debt to Finlay. But Finlay really didn't get much formal recognition in the US There was a much bigger focus on Walter Reed.

[Tracy V. Wilson]

There was also a big focus on how this discovery was connected to the military and military readiness. In 1900, US Army General Leonard Wood, who was a physician and military governor of Cuba, said, quote, the confirmation of the doctrine of Dr. Finlay is the biggest, biggest step that has been given in medical science after the discovery of Jenner's vaccine. And this single fact is enough to justify the war against Spain.

[Holly Fry]

That recognition of Finlay did not carry throughout the army. At the Pan American Medical Congress In February of 1901, the American army board gave a presentation that made this discovery sound like it was Walter Reed's work. That happened at a session Finlay was presiding over. Cuban delegates to this congress were absolutely furious.

[Tracy V. Wilson]

But Finley got more recognition in Europe and in Cuba, he became a national hero. He was appointed chief sanitary officer of Cuba after Cuba became formally independent in 1902. This work included mosquito control and eradication program, something that had started all across areas that were affected by yellow fever. As soon as Reid made this announcement, these efforts led to yellow fever being eradicated in the southern United States and in a number of tropical cities and towns. Although these mosquito control efforts involved the use of insecticides that did not target only mosquitoes, they killed other insects as well, and the insecticides also had other health effects of their own.

[Holly Fry]

Finlay continued to work on matters of public health in Cuba, including an anti infantile tetanus campaign. This included research carried out in 1903 which showed that wicks that were being used to tie off the umbilical cords of newborns provided a favorable medium for tetanus to grow. Findlay developed a program for distributing aseptic packages for treating the umbilical cord to poor parts of Cuba, and that led to a steep drop in infantile tetanus rates.

[Tracy V. Wilson]

Finley retired in 1909. In 1911, the New York Times published a piece titled Dr. Finlay Gets Full credit Now. Havana physician who solved the yellow fever problem is extolled here and abroad using the name Charles, which Finlay did use himself in work that was published in English. It described his research prior to the arrival of the Reed Commission. And it summarized a paper written by a doctor from Edinburgh who wrote in part, quote, considering the Times, it will eventually be considered one of the most wonderful pieces of constructive work in the history of medicine. But like every other advance, it was rejected by contemporaries. Unlike nearly all other great medical discoverers, however, he has lived to see the acceptance of his facts and has not had to die of a broken heart.

[Holly Fry]

Heart.

[Tracy V. Wilson]

But it has been enough to break anyone's heart to see himself so utterly ignored while the world has been singing the praises of the men upon whom he forced his ideas.

[Holly Fry]

Carlos Juan Finlay died on August 20, 1915, at the age of 82. He had written 40 articles on yellow fever over the course of his career and many, many other articles on other diseases and conditions over the course of his life. He was nominated for the Nobel Prize in physiology or medicine seven times, but he was never awarded it.

[Tracy V. Wilson]

He was briefly acknowledged when Max Thyler was awarded the Nobel Prize in 1951 for his discoveries concerning yellow fever and how to combat it. Those discoveries included an attenuated form of the virus that could be used as a vaccine. Part of the presentation speech said, quote, as early as the 18th century, the abundance of mosquitoes in places where the disease occurred has been observed. And in 1881, Dr. Carlos Finlay, a Cuban physician in Havana, had written a treatise in which he asserted that the disease was transmitted by mosquitoes. But his assertion drew little attention.

[Holly Fry]

As we said earlier, Finlay became a national hero in Cuba. He was honored with postage stamps and street names. The Finlay Institute for Investigations in Tropical Medicine was established in his honor after his death in 2013. He was also honored with a Google doodle for his 180th birthday.

[Tracy V. Wilson]

Yellow fever, of course, still exists today. Researchers started discovering viruses and differentiating them from bacteria and toxins at the very end of the 19th and early 20th centuries. The yellow fever virus was isolated for the first time during a massive outbreak in Africa in 1927. Today, the World Health Organization lists 27 countries in Africa and 13 in Latin America as at high risk for yellow fever outbreaks.

[Holly Fry]

Protection from mosquito bites, eliminating stagnant water and mosquito eradication programs can all reduce the risk of yellow fever outbreak and outbreaks of other mosquito borne diseases. But the disease cannot be eliminated entirely. In addition to Aedes aegypti, which lives in urban areas, it can also be carried by other mosquitoes that live in the jungle and feed primarily on monkeys. So there's ongoing circulation of the disease in jungle environments, which can then be carried back to human settlements when people get bitten in the jungle and then return home. Yellow fever is vaccine preventable today. And while there are some antiviral treatments that are used on occasion, there's no specific yellow fever antiviral. Most people who contract it receive supportive care.

[Tracy V. Wilson]

So that's Carlos Juan Findlay. Finally, after many years of wanting to do this episode.

[Holly Fry]

Do you have a listener mail? I wanted to say listener mail that you've been waiting to read for several years, but I know that's not true. No.

[Tracy V. Wilson]

I mean, I could try to look for some from way way in the past, but I won't. Rather than reading a specific mail, I wanted to talk generally about the theme of some email, because when we did our episode on Bhagat Sing Thind, we talked about how to pronounce the religion Sikh and how there are people who pronounce it Sikh. And we have gotten some feedback from folks whose relatives who immigrated from India do pronounce the at Sikh. So I wanted to talk a little bit more about that. The people that I listened to on how to pronounce this name are themselves Sikhs. Some of them are Sikhs from India or somewhere else in the Indian subcontinent or immigrants to the United States who are Sikhs. And they were pretty specifically adamant that Sikh is the correct pronunciation. Although, as we said, there's some nuance and how to pronounce it with that vowel sound that I cannot hear the difference.

[Holly Fry]

Right.

[Tracy V. Wilson]

And how it's being said that said, the pronunciation of Sikh was incredibly widespread here in the U.S. incredibly widespread in former British territory, in what's now like India and Pakistan and Bangladesh and all of that. And so the way it's really been characterized is the pronunciation of Sikh being a pronunciation that evolved because of British colonization of that part of the world. And that the pronunciation of sic is like reclaiming the correct pronunciation from one that had been Anglicized many years ago. Absolutely unsurprising that people's maybe older relatives, maybe people who came to the United States a long time ago, might be using the pronunciation Sikh. And that might sound correct because that's the one that they grew up with and have always used. But a lot of people have talked about trying to reclaim the pronunciation of sic as the correct pronunciation now today. So, yeah, I think Holly and I, when you and I were talking about it, we both had always heard the pronunciation seek from earlier in our lives.

[Holly Fry]

Yeah.

[Tracy V. Wilson]

And all of that. So I just wanted to give a little more context. Context to that after getting some email about it. If you would like to send us an email about anything, we'[e-mail] and if you want to find the show notes to this episode with all of our research that we used, it is at our website, which [e-mail] and you can subscribe to the show on the iHeartRadio app and anywhere else you'd like to get your podcast Podcasts. Stuff youf Missed in History Class is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.

[Holly Fry]

Living with a rare autoimmune condition brings uncertainty, but it can also create community In Season six of Untold Life with a Severe Autoimmune Condition, they go beyond MG and cidp. Host Martine Hackett welcomes stories from other conditions like myositis and IGAN into the conversation. Untold Stories is produced by Ruby Studio in partnership with Argenics. Listen to Untold Stories Life with a Severe Autoimmune condition on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Wouldn't it be great to never buy gas again? EVs are as easy to charge as your phone, and they are a perfect addition to your everyday life. Most people are only driving about 40 miles a day, and most EVs can handle 200 to 400 miles of RA a charge. And there are hundreds of EV models available today, so there's something perfect for every lifestyle and budget. I drive an ev. I've had it for a couple of years. It's my favorite car I've ever owned. It is so fun to drive. The pickup is incredible. It's super agile and it is easy to maintain. The way forward is electric. Learn [e-mail] brought to you in part by Vital Farms.

[Tracy V. Wilson]

I love eggs. I turn to them all the time as a quick and easy way to start a meal. And Vital Farms eggs are brought to pens that have access to fresh air and sunshine, and you can actually look up on the carton and see the farm that those eggs came from. Vital Farms is also a certified bee corporation with a purpose to improve the lives of people, animals and the planet through food. Look for the black egg carton in the egg aisle and visit vitalfarms.com to learn more. Vital Good Eggs no Shortcuts these days

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[Tracy V. Wilson]

This is an iHeart podcast. Guaranteed Human.