Carlos Juan Finlay was a Cuban physician and biologist, who, in 1881, suggested that yellow fever, an acute febrile illness fatal to half its victims, was transmitted by mosquitoes. His theory, confirmed in 1900 by the American surgeon Walter Reed, led to widescale control of the disease. Finlay also made important contributions toward the understanding of infant tetanus and of cholera.
Carlos Juan Finlay was born in Camagüey, Cuba, on December 3, 1833. He was one of seven children born to Edward Finlay, a Scottish physician who had fought alongside Simon Bolivar, and Eliza Isabel, née deBarrés, a French woman. The family owned a large coffee plantation in Guanimar, in the Alquizar region of Cuba. Finlay spent his early childhood on this plantation and in a family home in Havana. He received his schooling from his paternal aunt, Ana, who had started a school in Edinburgh, Scotland, but had returned to Cuba to live with her brother's family. In 1844 Finlay was sent to La Havre, France, to begin his formal education. Two years later, suffering from an attack of chorea, a condition in which facial and limb muscles contract spasmodically, he returned to Cuba. After extensive therapy in his father's medical institute, he returned to Europe in 1848, intending to complete his education in France. Political turmoil across the European continent forced him to remain in England for two years. When he finally entered the lycée in Rouen, his studies were interrupted once again, this time because he had contracted typhoid fever. After a period of convalescence in Cuba, he attempted to enroll in a medical training program at the University of Havana. It was not possible to transfer his European credits, and the only program he could enter without prerequisite courses was in Philadelphia, at the Jefferson Medical College. His decision to study in Philadelphia was to have a major impact on his future career, for it was here that he met and befriended the family of John Kearsly Mitchell. Mitchell was an outspoken proponent of the Germ Theory of disease, which held that illness was caused by micro-organisms. He and his son S. Weir Mitchell were professors at Jefferson Medical College. The younger Mitchell directed Finlay's studies for three years, and was to become a lifelong friend. Finlay received his medical degree on March 10, 1855.
Although Mitchell attempted to convince Finlay to remain in America and set up a practice for the Spanish community in New York City, Finlay decided to return to Havana and work alongside his father. Together they made several trips to South America, treating a wide diversity of patients. It is likely that while on these trips, the younger Finlay encountered many victims of yellow fever. The disease was also endemic in the Caribbean. In 1857, after obtaining certification in Cuba, he set up a practice in ophthalmology. From 1860 to 1861, he went to Paris for additional clinical study. In 1865 Finlay married Adela Shine, from the island of Trinidad. Together they had three sons, Charles, George and Frank. The family was regarded highly in Cuban society and Finlay distinguished himself as a dedicated and caring physician. In the 1860s and 1870s there were frequent outbreaks of yellow fever, and Finlay observed that the disease seemed to be transmitted from one person to another. He postulated that the agent of transmission was the mosquito. In 1881 he was invited to speak before the International Sanitary Conference in Washington DC, as a representative of the Cuban colonial government. European scientists had begun to identify the infectious agents of several other illnesses and Germ Theory had now gained hold. Finlay's notion that yellow fever could be transmitted to humans by mosquitoes was well received.
In June of 1881 Finlay began a series of experiments to test his theories. He bred Aedes aegypti mosquitoes in captivity, and allowed them to feed on blood drawn from victims of yellow fever during the early stage of their illness. He then transported the mosquitoes to human volunteers, who were bitten by the insects. His goal was to see if he could induce a mild form of yellow fever that could confer immunity on the volunteers. In 1888, when the Spanish American War broke out, Finlay offered his services to the United States government. He befriended the director of military health, who sent him to work with American troops in Santiago de Cuba. He continued his experimentation, using soldiers as subjects, and by 1898 had collected a wealth of data which he presented to the military officials. It is unlikely, in light of what is now known about the length of incubation of yellow fever in the Aedes aegypti mosquito, that many of Finlay's early human experiments were successful. Nonetheless, his research laid the foundation for the success of others. In 1900, when Walter Reed (1851-1902), a major in the United States Army Medical Corps, began the definitive studies of yellow fever transmission, Finlay supplied him with the mosquitoes he had bred.
The pioneering studies that Finlay conducted and Reed was to successfully complete led to the eventual control of yellow fever around the world. In 1902, the government of Cuba honored Finlay by naming him the Chief of Health of the Republic and the President of the Superior Commission of Health. Finlay began, the next year, to tackle a new medical problem. Alarmed at the high rate of infant mortality from tetanus, he examined the pieces of cotton cording traditionally used for tying the umbilicus at birth. Finding them to be a nest for tetanus bacteria, he implemented a new sterile process. The mortality from tetanus was cut in half almost immediately. Finlay went on to make advances in the study of filarial illnesses and cholera. He was a prolific writer on the topics of pathology and therapeutics. As a hobby, he spent time deciphering antique Latin manuscripts, and enjoyed playing chess. In his seventies he began a study of immunology. Finlay died in 1915, at the age of eighty two.
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