Origin of yellow fever

Enrique Chaves-Carballo 
Kansas City, Kansas, United States

 

Photo of Henry R. Carter, researcher into the origin of yellow fever
Henry R. Carter (1852-1925), Public Health Service Assistant Surgeon General and yellow fever epidemiologist. Credit: Wellcome Collection. Attribution 4.0 International (CC BY 4.0)

The origin of yellow fever has been a controversial subject since the disease appeared in the New World. William C. Gorgas, who was responsible for the sanitation of Cuba and Panama, believed that yellow fever originated in Panama.1 Henry R. Carter, from the U.S. Marine Hospital Service and director of hospitals and chief quarantine officer of the Isthmian (Panama) Canal Commission, wrote an exhaustive treatise on the origin of yellow fever: Yellow Fever. An Epidemiological and Historical Study of its Place of Origin.2 Carter was convinced (as also was Walter Reed) that yellow fever originated in Africa and was brought to the New World by slave trade ships.

 

African origin

Carter argued that descendants of slaves brought to America from West Africa appeared to have an inherent immunity to yellow fever, resulting in milder cases and lesser mortality than in European victims. This resistance to disease must have required repeated exposure to the virus over a prolonged period of time before becoming a genetic trait. Carter also analyzed reported outbreaks of deadly epidemics in Mexico and the Caribbean and concluded that none of these were convincingly yellow fever. Havana, which became an endemic focus of yellow fever and, according to Gorgas, suffered over 23,000 deaths between 1871 and 1900, did not report its first outbreak until 1649.1

Carter concluded that the first bona fide outbreak of yellow fever in America occurred during the battle of Vega Real in Hispaniola (Haiti) in 1495 between the expeditionary forces of Columbus and the local indigenous peoples, resulting in heavy mortalities. With regard to the vector Aedes aegypti, Carter argued that this mosquito required environmental conditions present in both tropical climates of Africa and America, so that it could either already have been present in the New World or transported by ships from Africa. However, several species of Aedes were described in Africa but no other variations in the New World, suggesting Aedes had resided in Africa much longer than in America. Carter explained the paucity of historical records of yellow fever from Africa by the lack of reports by European explorers from that continent and the unreliability of oral histories from tribal leaders. In contrast, Spanish and Portuguese explorers in America recorded meticulously every illness encountered among themselves and in indigenous populations. Despite this discrepancy, Carter found no convincing reports of yellow fever among ancient Maya and Aztec records. This assertion had the credibility of an expert epidemiologist who experienced and studied yellow fever for many years.2

More recent phylogenetic studies, including genomic analyses of yellow fever virus strains from Africa and South America, imply that the virus originated in Africa within the last 1,500 years and emerged in the Americas approximately 300 to 400 years ago, coincident with the slave trade.3

 

American origin

Carlos E. Finlay, son of Carlos J. Finlay, discoverer of the mosquito as the vector of yellow fever, indicated that Maya records accurately described epidemics of a deadly disease called xekik (black vomit). Black vomit is a characteristic sign of fatal yellow fever and, coincidentally, yellow fever was also called black vomit in America. Yellow fever is a hemorrhagic fever causing copious gastric bleeding. When blood admixes with acid in gastric juices, it turns black and induces protracted vomiting. Similarly, in Yucatan a pestilence called cocoliztle by the aborigines appeared for the fourth time in 1648, suggesting it had been there long before the Spanish conquest.4

The Maya calendar system was based on astronomical observations and can be accurately translated into modern calendar dates. The fundamental unit was the kin (day), followed by the tun (year or 360 days), and Katun (20 tuns or 20 years). Thus, dates listed in Aztec and Mayan codices such as the Chilam-Bayan, can readily be translated to our Gregorian calendar. These ancient records assert that black vomit had afflicted the Maya population already four times by 1648. This strongly suggests the presence of yellow fever in America may have antedated the arrival of slave and trade ships from Africa and Europe. Many precious Maya codices and manuscripts owned by Bishop Diego de Landa were burned in an auto da fe (act of faith) by him in 1562, a common practice encouraged by the Spanish Inquisition in a futile attempt to eradicate heretical records found among the Maya and Aztecs, destroying in this manner valuable records that may have clarified further the origin of yellow fever in the Americas.4

Carter’s exhaustive research and credible arguments support the origin of yellow fever from Western Africa brought by slave and trade ships to the New World. However, the exactitude of the Maya calendar and their assertion that xekik (black vomit) had already visited them several times before 1648 strongly suggests that yellow fever was already endemic in the New World before the arrival of Europeans. Particularly convincing is that the Maya used the same terminology of black vomit to describe yellow fever as is still used today.

It is difficult, if not impossible, based on the available evidence to ascribe the origin of yellow fever definitively. Strong arguments support either Africa or America as the possible source of the yellow scourge.

 

References

  1. Gorgas WC. Sanitation of Panama. New York: D. Appleton & Co., 1915.
  2. Carter HR. Yellow Fever. An Epidemiological and Historical Study of its Place of Origin. Baltimore: The Williams & Wilkins Company, 1931.
  3. Bryant JE, Holmes EC, Barrett AD. Out of Africa: Perspectives on the introduction of yellow fever virus into the Americas. PLoS Pathogens; 2007. https://doi.org/10.1371/journal.ppat.0030075
  4. Finlay CE. Carlos Finlay and Yellow Fever. New York: Oxford University Press, 1940

 


 

ENRIQUE CHAVES-CARBALLO, MD, is a pediatric neurologist and clinical professor emeritus, Department of History and Philosophy of Medicine, Kansas University Medical Center. He received his medical degree from the University of Oklahoma and trained in pediatrics and neurology at Mayo Clinic, Rochester, MN. His main research interest is the medical history of the Panama Canal and he has published several articles and books on tropical diseases, yellow fever, malaria, and Samuel Taylor Darling.

 

Fall 2020 |  Sections  |  Infectious Diseases