[137][138][139] Over the course of several days, he became severely ill with an unknown digestive ailment initially resembling acute gastroenteritis. The illness initially seemed mild, and on the first day Taylor felt well enough to continue working. His condition worsened thereafter. His Army physician Alexander S. Wotherspoon "diagnosed the illness as cholera morbus, a flexible mid-nineteenth-century term for intestinal ailments as diverse as diarrhea and dysentery but not related to Asiatic cholera", the latter a widespread epidemic prevalent in Washington DC at the time of Taylor's death.[136][140] The identity and source of Taylor's illness are the subject of historical speculation .mw-parser-output div.crossreference{padding-left:0}(see below), although it is known that several of his cabinet members had come down with a similar illness.[141]
Fever ensued and Taylor's chance of recovery was small. On July 8, Taylor remarked to a medical attendant:

I should not be surprised if this were to terminate in my death. I did not expect to encounter what has beset me since my elevation to the Presidency. God knows I have endeavored to fulfill what I conceived to be an honest duty. But I have been mistaken. My motives have been misconstrued, and my feelings most grossly outraged.