Carlos Finlay, the doctor who discovered that a mosquito transmitted yellow fever and was ignored by his peers

Cuban doctor Carlos Finlay, who verified that a mosquito is the transmitter of yellow fever.

He had recognitions in life but began to pay tribute 38 years after his death when, with justice, it was determined that his date of birth was instituted as Doctor’s Day. Carlos Juan Finlay y Barré had spent their entire lives investigating what caused yellow fever and when he discovered that the culprit was a mosquito, no one believed him.

He would never forget August 14, 1881 when he gave the results of his studies in the dissertation “The mosquito hypothetically considered as a transmission agent of Yellow Fever”, which he delivered in the ordinary assembly of the Royal Academy of Medical, Physical and Natural Sciences of Havana that worked on the first floor of the former convent of San Agustín, an ancient building founded by the Spanish in the seventeenth century.

It was the result of years of research that dismantled old, unprovable conceptions that this disease was transmitted through the air and by direct contact. Finlay assured that the female of the Aedes Aegypti was the culprit of the spread of a scourge that revealed to the world scientific community. Smiles, murmurs, and a thunderous silence preceded the departure from the doctors’ room. They turned their backs on him.

Carlos Finlay's presentation of 1881.
Carlos Finlay’s presentation of 1881.

He was used to it by now. When on his return from a study trip to Europe, he announced that cholera was transmitted through the Zanja Real – the first aqueduct that supplied drinking water to the Cuban capital – that passed through the Cerro neighborhood where he lived, he was forbidden to publish it . It was wartime and it was not convenient. It would only become known in 1873, when the epidemic had already passed.

With a Scottish surname, he was born in Cuba because his father Edward, a doctor who wanted to enlist in Simón Bolívar’s army, traveled on a ship that was wrecked, got married in Trinidad and Tobago and moved to the current town of Camagüey.

In 1855 he graduated from Jefferson Medical College, in the United States, a country in which the admission regime was much more flexible than in Spanish Cuba at the time. There studied with Professor John Mitchell, proponent of the groundbreaking theory that germs were transmitters of disease. Mitchell’s teachings stayed with him throughout his life: he stressed the importance of observation and investigation.

The study of the spread of cholera and smallpox became his obsession. Finlay also investigated cancer surgery, the harmful effects of birth gas, leprosy, and tetanus in newborn children.. Even so, with this background, the Royal Academy of Medical, Physical and Natural Sciences took seven years to accept him as a member.

The plaque at the entrance to the museum that bears the name of the Cuban doctor.
The plaque at the entrance to the museum that bears the name of the Cuban doctor.

In February 1881, at the Sanitary Conference held in the United States, he had already anticipated the existence of an independent agent for yellow fever and the patient. Together with his collaborator the Spanish doctor Claudio Delgado and Amestoy between 1881 and 1900 they carried out hundreds of experiments to be able to reliably demonstrate his theory, aided only with his old microscope that had accompanied him since his student days. It was on June 30, 1881 when he carried out the first experimental test with a mosquito.

In the following years, he had the help of Spanish priests who arrived on the island, who volunteered to undergo his tests.

Scientific commissions sent to Cuba in the last years of the century did not take into account the Cuban’s conclusions. And he, meanwhile, insisted on the destruction of mosquito larvae and called for the implementation of prophylactic measures. But there was no case; He did not have influential friends and the closeness of his colleagues prevented him from being heard.

It took a war to be listened to.

Bust in tribute to the Cuban doctor and scientist.  In his honor, the day of his birth is commemorated Doctor's Day.
Bust in tribute to the Cuban doctor and scientist. In his honor, the day of his birth is commemorated Doctor’s Day.

During the conflict between the United States and Spain over Cuba in 1898, Americans were more concerned with soldiers dying each day from yellow fever than by casualties on the battlefields. Leonard Wood, the island’s military governor, who was also a doctor, asked the United States government to send a commission to study why his soldiers died like flies from yellow fever, also known as “black vomit.” .

Two doctors who were part of that commission and who investigated malaria, recommended that attention be paid to the investigations of the Cuban. One of them, Jesse Lazear, was the most convinced that Finlay was on the right track, to the point that he died to prove him right.

It is that Lazear himself and other volunteers allowed themselves to be bitten by mosquitoes obtained from eggs provided by Finlay, and that they had ingested blood from yellow fever patients two weeks before.

Lazear, physician James Carroll, and Private William Dean became ill voluntarily. Lezear kept a diary in a small notebook, where he described the symptoms day by day. His last entry was on the 13th, when he passed away. It was September 25, 1900. Yet Finlay still failed to overcome the reluctance of the scientific world.

The doctor Jesse Lazear, who supported Finlay in his investigations, ended up being a victim of yellow fever.
The doctor Jesse Lazear, who supported Finlay in his investigations, ended up being a victim of yellow fever.

It was necessary to wait for the following year with the successful campaign of the American military doctor William Gorgas. The US occupation government was cornered by criticism from Cubans, who accused it that there were more and more patients with yellow fever and that it was doing nothing. So he applied Finlay’s advice, and with the launch of the “War to the Death against the Mosquito” campaign, eradication of the disease began.

When Cuba declared its independence, Finlay was appointed Superior Chief of Health. It had its litmus test in 1905, when in three months it eliminated the yellow fever epidemic that had been unleashed. And no one could take away the merits. A 250-year history of this scourge in Cuba would end.

Since 1905, Finlay has been nominated for the Nobel Prize, with no luck. He died in Havana on August 20, 1915, at the age of 82.

Today there is the “Carlos J. Finlay” order of merit to those who provide relevant services to science. In the Royal Academy of Medical, Physical and Natural Sciences there is a museum that bears his name, which tells the story of a Cuban, with a Scottish surname and that one day an American ended up agreeing with him.


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