THINKER'S ALMANAC - December 3

Subject: Illusion of Knowledge - Yellow Fever

Event:  Birthday of epidemiologist Juan Carlos Finlay, 1833

In 1881, epidemiologists -- disease detectives -- were searching for the cause of yellow fever.  Conventional wisdom at the time was that it had something to do with unsanitary conditions and unhealthy air.  

One doctor, however, had a different hypothesis.  He was the Spanish, Cuban epidemiologist named Juan Carlos Finlay, who was born on this day in 1833.  Finley noticed a correlation between the presence of the Culex mosquito and yellow fever.  It seemed that the warm weather that brought the Culex also inevitably brought yellow fever.  However, when the weather cooled and the Culex disappeared, so did yellow fever.

Finlay tested his hypothesis by having mosquitoes first bite patients with yellow fever and then bite healthy patients.  The healthy patients, however, failed to get sick.  Based on this evidence, Finlay’s hypothesis was disregarded.

One American doctor, however, remembered Finlay’s mosquito hypothesis when yellow fever broke out where he was working in Mississippi.  Henry Rose Carter noted a pattern of yellow fever outbreaks aboard ships that arrived at port in the southern United States.  Initially, there might be some cases, but then there appeared to be a period of around two weeks before other cases developed.  This caused Carter to hypothesize that there might be a short incubation period.

In 1901, Carter was reassigned to Havana, Cuba, as a quarantine officer.  There, he was able to persuade his superior, Water Reed, to put his mosquito hypothesis to the test.  Two of Reed’s assistants, Jesse Lazear and James Carroll, agreed to use themselves as guinea pigs.  They first had mosquitos bite patients with yellow fever.  They then waited for twelve days before letting the mosquitoes bite them.  Confirming Carter’s hypothesis, both Lazear and Carroll came down with yellow fever, and unfortunately, Lazear’s case was so severe that he died.

The work of all these doctors to discover the cause of yellow fever confirms what the historian Daniel Boorstin about learning: “The greatest obstacle to knowledge is not ignorance; it is the illusion of knowledge.”  Lazear’s initial hypothesis seemed crazy; after all, how could such a tiny insect be the cause of the death of so many people?  It seemed much more plausible that the cause must be the unhealthy conditions revealed by the stench in the air.

Challenge - Heroes of Epidemiology: Do some research on epidemiologists who have made great contributions to public health.  Identify one person, and explain his or her specific contribution.

Sources:

1-Klein, Gary. Seeing What Others Don’t. London: Nicholas Brealey Publishing, 2013.