On the history of Ebola and viral hemorrhagic fevers

No outbreaks of Ebola had ever been reported in this part of Africa before³. Earlier outbreaks did not reach these proportions and all appear to have been quashed after routes of transmission were traced and controlled. Some of these outbreaks were at least partially facilitated by inadequate hospital hygiene⁴. In contrast, the current “outbreak” appears to have longresisted  control measures with numbers of cases doubling within two weeks^1 5. 

Marburg fever, a related viral hemorrhagic fever (VHF), also appears to have never occurred in major epidemics⁴.  

A remarkable aspect of these lethal VHF viruses is that they were only discovered in the 1960s and 1970s^3 4. Ebola was first identified in outbreaks occurring in Yambuku, Zaire and Nzara, Sudan (now South Sudan) in 1976³. It seems unlikely that cases or outbreaks never occurred before, and if occurred, it seems difficult not to be noticed and described by travelers or colonial authorities or missionary hospitals. Consider a narrative from 1865 by the explorer Samuel Baker from the South of Sudan, an area close to Nzara where the 1976 outbreak occurred, which offers some insight⁶. While Baker calls the disease “the plague”, it is evident that the symptoms do not resemble the disease caused by Yersinia pestis, but describe a lethal form of hemorrhagic fever, perhaps Ebola, as the following excerpt narrates:

“All before us was clear and plain sailing. For some days two or three of our men had been complaining of severe headache, giddiness, and violent pains in the spine and between the shoulders. I had been anxious when at Gondokoro concerning the vessel, as many persons while on board had died of the plague, during the voyage from Khartoum. The men assured me that the most fatal symptom was violent bleeding from the nose; in such cases no one had been known to recover. One of the boatmen, who had been ailing for some days, suddenly went to the side of the vessel and hung his head over the river; his nose was bleeding!

Another of my men, Yaseen, was ill; his uncle, my vakeel, came to me with a report that "his nose was bleeding violently!’ Several other men fell ill; they lay helplessly about the deck in low muttering delirium, their eyes as yellow as orange-peel. In two or three days the vessel was so horribly offensive as to be unbearable. The plague has broken out!  We floated past the river Sobat junction; the wind was fair from the south, thus fortunately we in the stern were to windward of the crew. Yaseen died; he was one who had bled at the nose. We stopped to bury him. The funeral hastily arranged, we again set sail. Mahommed died; he had bled at the nose. Another burial. Once more we set sail and hurried down the Nile. Several men were ill, but the dreaded symptom had not appeared. I had given each man a strong dose of calomel at the commencement of the disease; I could do nothing more, as my medicines were exhausted. All night we could hear the sick muttering and raving in delirium, but from years of association with disagreeables we had no fear of the infection.

One morning the boy Saat came to me with his head bound up, and complained of severe pain in the back and limbs, with all the usual symptoms of plague. In the afternoon I saw him leaning over the ship's side; his nose was bleeding violently! At night he was delirious. On the following morning he was raving, and on the vessel stopping to collect firewood he threw himself into the river to cool the burning fever that consumed him. His eyes were suffused with blood, which, blended with a yellow as deep as the yolk of egg, gave a terrible appearance to his face, that was already so drawn and changed as to be hardly recognized. Poor Saat! The faithful boy that we had adopted, and who had formed so bright an exception to the dark character of his race, was now a victim to this horrible disease. He was a fine strong lad of nearly fifteen, and he now lay helplessly on his mat, and cast wistful glances at the face of his mistress as she gave him a cup of cold water mixed with a few. An hour passed, and he slept. Karka, the fat, good-natured slave woman, quietly went to his side; gently taking him by the ankles and knees, she stretched his legs into a straight position, and laid his arms parallel with his sides. She then covered his face with a cloth, one of the few rags that we still possessed. ‘Does he sleep still?’ we asked. The tears ran down the cheeks of the savage but good-hearted Karka as she sobbed, ‘He is dead’.”

Texts like these pinpoint potential hot spots for Ebola outbreaks, and reveal the epidemiology of these VHF viruses in absence of modern control measures. 

Baker's book is available online and it is plausible that there could be similar sources that can be scrutinized for evidence and insight. However, most relevant texts are not and probably have never been published. Studying outbreaks during colonial and missionary times for clues would require extensive research into a multitude of documents, as the names Ebola and Marburg were not yet given to these diseases. 

Yet, these texts can help us understand the frequency of the outbreaks, and provide insights into the nature of “spillover events” from the animal reservoir and their socio-economic, cultural, and climatological associations.

Nico Nagelkerke is a biostatistician and epidemiologist at the Erasmus Medical Center, Rotterdam, The Netherlands and Laith J. Abu-Raddad is an epidemiologist at the Weill Cornell Medical College in Qatar.

Funding acknowledgement:“Laith Abu Raddad acknowledges the support provided by the National Priorities Research Program, grant number NPRP 4-924-3-251, from the Qatar National Research Fund (a member of Qatar Foundation).”

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