New research indicates that Sir Arthur Conan Doyle, the creator of the fictional detective Sherlock Holmes, may have anticipated significant medical discoveries years before they were scientifically proven. His second Holmes novel, "The Sign of Four," published in 1890, appears to allude to the theory that malaria is spread by mosquitoes and describes the disease kala-azar, or black fever, more than a decade before its official identification.
Professor Mike Barrett of Glasgow University suggests that Doyle, who practiced as a general physician before achieving literary fame and had a strong interest in tropical and infectious diseases, was ahead of his time. Barrett's research focuses on the character Major John Sholto, whose mysterious illness and death in the novel may represent an accurate depiction of kala-azar, a tropical disease prevalent in India at the time.
The symptoms described for Major Sholto, including an enlarged spleen and a history of poor health since returning from India, alongside his use of quinine, hint at a suspected malaria diagnosis. However, Barrett posits that Doyle might have been describing kala-azar, a disease not formally identified until 1903 by scientists like Sir William Boog Leishman. Kala-azar, caused by infected sandfly bites, remains a public health issue in certain regions. Doyle "provides some of the earliest literary depictions of visceral leishmaniasis [kala-azar] and remarkably did so over a decade before its cause was even known," Barrett stated.
Malaria Transmission Theory
The novel also includes details about Jonathan Small, a character who describes his time in the Andaman Islands as living in a "fever-ridden swamp" and being "bitten by mosquitoes." At the time "The Sign of Four" was published, the existence of malaria was known, but the transmission of the disease by mosquitoes had not yet been scientifically proven. This confirmation came in 1897 with Sir Ronald Ross's work demonstrating that malaria parasites are spread by Anopheles mosquitoes.
Barrett argues that Doyle's depiction, linking mosquitoes, swamps, fever, and "ague" (a common Victorian term for malaria), suggests an early alignment with the theory of mosquito transmission. This theory was being advanced by Sir Patrick Manson, a pioneer in tropical medicine, before Ross's definitive proof. Barrett's analysis indicates that Doyle was describing the disease in a manner consistent with mosquito transmission approximately seven years before Ross's discovery.
Malaria, historically thought to be caused by swamp miasma ("mal'aria" in Italian), was identified as parasitic in 1880 by Alphonse Laveran. Ross later showed the parasites were transmitted by mosquitoes, a discovery for which he received the Nobel Prize. Doyle's narrative, with Small's account of being "bitten by mosquitoes, racked with ague," appears to incorporate this emerging understanding of disease transmission.