Yellow Fever in the US: The Final Battle

Mosquito Larvae Suspended in a Water Droplet Photo: Dr. John H. Brackenbury

In 1900, Walter Reed’s team in Cuba produced solid evidence for the “Mosquito Doctrine of Yellow Fever Conveyance”. This doctrine allowed medical and public health personnel to focus on eliminating mosquito breeding sites and isolating infected patients from mosquitoes as means of halting Yellow Fever epidemics. The Yellow Fever mosquito, Aedes aegypti, breeds in stagnant water. Eliminating cisterns and other small containers of water as breeding sites for the mosquito was a key to halting the epidemic. A tactic as simple as covering cisterns with cheesecloth could save hundreds of lives.

Dr. Quitman Kohnke, the Health Officer for New Orleans in 1905 summarized his efforts in a lecture that was published as a paper, The Yellow Fever epidemic of 1905 in New Orleans.* He described the steps taken to control the epidemic and viewed his work as a definitive successful experiment.

For the final acceptance of what is called the mosquito doctrine of disease conveyance, as applied to yellow fever there was needed an object lesson, planned on a large scale; and New Orleans was offered up in sacrifice to furnish the demonstration.

The first step was to forcibly seize an unoccupied building in the infected area and convert it into a hospital with windows “screened” to exclude mosquitoes. He proudly notes “No case of Yellow Fever originated in this hospital…”. He chastises well-meaning and prominent citizens for clinging to the “fomites” theory of Yellow Fever and making his job of education and proper remediation more difficult.

Yellow Fever is conveyed in one way only. The Stegomyia (=Aedes) mosquito obtains the germ of the disease by feeding on the patient during the first three days of illness; the germs reach the salivary glands of the insect in twelve days, and not until then is the mosquito infectious; therefore, to keep mosquitoes from biting a patient during the first three days of his disease will prevent infection of mosquitoes; to destroy mosquitoes already infected prior to the expiration of the twelve day period will prevent infection by them of persons.

Knowledge of the way in which yellow fever is spread points logically to its prevention; but it is a far cry from the discovery of a scientific truth to its general acceptance by a community, and the hardest of our work was the instruction of the ignorant and the removal of prejudice against the new doctrine.

Dr Kohnke persevered in spite of attacks from the press and part of the “old school” medical establishment. Old beliefs die hard and some people refuse to accept scientific findings and knowledge to their own detriment. “Anti-science sentiment” persists among parts of the US public and some political leaders in spite of numerous cautionary tales. The 1905 Yellow Fever epidemic was brought under control primarily by exclusion of Yellow Fever mosquitoes from breeding sites and blocking access to infected patients.

You see here the same cisterns, covered with cheese-cloth to prevent the entrance of mosquitoes after the oiling of the water surface to kill those not yet developed into adults. This picture is a little too intensely colored, but everything about New Orleans was highly colored at that time – especially the libelous statements against the health authorities, extensively published by many of the yellow journals, and, I regret to say, by a portion of the medical press.

Fortunately, the advice of Dr Kohnke and like-minded science based professionals prevailed. Going forward, construction of better water storage that excluded Yellow Fever mosquitoes was an important step in the elimination of Yellow Fever epidemics in the United States.

*Public Health Pap Rep >v.32(Pt 1); 1906