In the late 1900s a French-Scottish physician called Carlos Juan Finlay had been practicing medicine in Cuba. One of the diseases that plagued the region was yellow fever. The popular belief in the medical profession was that yellow fever was caused by unhygienic and unsanitary conditions and that it most likely spread through the air or via physical contact. However, Finlay noticed that there were three unexplained coincidences – all three to do with mosquitos. First – areas where there was a certain type of mosquito – then called the Culex, there was yellow fever. And the inverse was also true – no Culex mosquito, no yellow fever. Second – he also saw that when the temperature dropped and it became too cold for the mosquito, yellow fever disappeared, only to reappear the next summer when temperatures rose and the mosquito returned. Third – he observed that the Culex mosquito didn’t tolerate higher elevations, and the people who lived at higher elevations escaped yellow fever. So, in 1881, Finlay proposed the theory that yellow fever was spread by mosquitos and not through the air or physical contact. The medical community ridiculed him calling him the mosquito man. He was labelled a crank and a crazy old man. In fact, an experiment he conducted actually demolished his own theory. He did studies where healthy volunteers allowed the Culex mosquito to bite them but none of them got sick. This for the medical community was solid evidence that the mosquito theory was incorrect. About 2 decades later, Walter Reed, a U.S. Army physician was sent to Cuba to study yellow fever. While he was there, he heard a report from southern United States about yellow fever outbreaks. A public health physician at the port in Mississippi, Henry Rose Carter, noted an incubation effect. He observed that if a ship with yellow fever victims landed, there were some immediate cases among fellow shipmates but the rest of victims got yellow fever only 12 days to 3 weeks later. Carter wondered about 12 days to 3 weeks incubation period. He speculated that those who were sick when the ship arrived were beginning to develop the disease. The others, who got yellow fever two weeks later, might have been bitten by mosquitoes that first feasted on the initial ship victims and then had time for the disease to mature inside them before they bit fresh victims. Carter tested this idea by regularly visiting the initial victims’ houses. He saw that anyone who visited the house in the first two weeks remained healthy. However, those that visited after the two weeks were at a risk of catching the disease even when the patient was no longer around. No longer around to transmit the disease through the air or physical contact. Carter reasoned that if the mosquitoes needed an incubation period before becoming infectious, it would explain why Carlos Finlay’s experiment to replicate the spread of yellow fever had failed. By a fortunate coincidence, Carter was posted to Havana, Cuba as the harbour quarantine officer. He met Walter Reed there and had a chance to influence him with his idea of an incubation period. Despite warnings from his superiors Reed started re-exploring Finlay’s mosquito hypothesis. While Reed was on a trip back to the US, two of his colleagues – James Carroll & Jesse Lazear, with Reed’s permission tried an experiment on themselves. They let a mosquito bite a someone with yellow fever and then let the same mosquito bite them after 12 days. This was the same experiment that Finlay had tried except they added the incubation period. The experiment was successful. In fact, fatally so. Jesse Lazear lost his life to yellow fever. Thankfully, James Carroll survived to tell the story. When Reed was back Carroll shared with him the results of the experiment. They now started several controlled experiments to demonstrate that the Culex mosquito was indeed transmitting yellow fever. To succeed in convincing the medical community Walter Reed not only had to fight the prevalent belief of transmission through air and physical contact but also fight the so-called proof of Finlay’s failed experiment. What an interesting turn of events! Business Points ( Tags ) #Persistence #Facingresistance #breakingbeliefsystem
