It cannot be said definitively what illness JA suffered from, for any diagnosis done more than two hundred years after the fact must in the end rest largely on speculation. Many of the medical terms current in the eighteenth century are either no longer used or have meanings different from those in JA’s day. Dr. Oosterdijk’s notes and testimony of his examination are unavailable and JA’s own descriptions, those of a layman, lack precision.

The inherent difficulty of diagnosing JA’s illness has not deterred some biographers from making the attempt. Peter Shaw, in the Character of John Adams (Chapel Hill, 1976, p. 150–152), and James H. Hutson, in John Adams and the Diplomacy of the American Revolution (Lexington, Ky., 1980, p. 97–98), see JA as mentally unstable, even paranoid, and conclude that his illness was psychosomatic. John Ferling, in John Adams, A Life (Knoxville, 1992, p. 237–238), wrote that JA contracted malaria, a view David McCullough shared in his John Adams (N.Y., 2001, p. 264–266). But Ferling, in an article entitled “John Adams’ Health Reconsidered” that he co-authored with Lewis E. Braverman (WMQ description begins William and Mary Quarterly. description ends , 3d ser., 55:83–104 [Jan. 1998]), declared that JA was likely a victim of Graves’ disease, so that his “behavior was not, as many have thought, the result of problems in his head or his heart, but in his thyroid.”

The editors believe JA’s illness was physical and most likely indigenous to the Netherlands. JA wrote to Ferdinand Grand on 12 Oct. (LbC, Adams Papers) that he was the victim of “an Amsterdam Fever, which they call an Introduction to the Freedom of the City,” implying that it was normal for one foreign to Amsterdam to fall ill in the course of acclimating himself to the locale. Indeed, on 5 Oct. Benjamin Franklin wrote: “I hope this Seasoning will be the means of securing your future Health, by accommodating your Constitution to the Air of that Country” (Adams Papers; Franklin, Papers description begins The Papers of Benjamin Franklin, ed. Leonard W. Labaree, William B. Willcox (from vol. 15), Claude A. Lopez (vol. 27), Barbara B. Oberg (from vol. 28), Ellen R. Cohn (from vol. 36), and others, New Haven, 1959– . description ends , 35:565–567). And JA later wrote that it was “the destiny of every stranger who goes into Holland to encounter either an intermittent or bilious fever within the two first years” (JA, Corr. in the Boston Patriot description begins Correspondence of the Late President Adams. Originally Published in the Boston Patriot. In a Series of Letters, Boston, 1809[–1810]; 10 pts. description ends , p. 533).

A diagnosis of malaria is attractive because it was endemic to the Netherlands, particularly in North Holland. Physicians would have been familiar with the symptoms and with the prescribed treatment: Peruvian bark or quinine. Moreover, from their reported symptoms it is likely that JA’s son CA, his servant Joseph Stephens, and his secretary John Thaxter all suffered from malaria.

But JA’s descriptions of his illness are at variance with the classic symptoms of malaria. Malaria is a periodic fever, that is, the victim suffers severe chills and then a fever that reaches a peak and then subsides, only to return two or three days later. In the intervals between the fever, the patient may appear and feel in good health. JA, however, nowhere describes his fever as periodic or “tertian,” as he does CA’s in the spring of 1781 (Adams Family Correspondence description begins Adams Family Correspondence, ed. L. H. Butterfield and others, Cambridge, 1963– . description ends , 4:108). Instead, he states that he suffered a high fever of at least five days’ duration and was unable to work for well over a month.

JA’s repeated statements that he suffered from a “nervous fever” present another possibility. The term “nervous fever” is another name for typhus in medical reference books of the time (Quincy’s Lexicon Physico-Medicum, 8th edn., N.Y., 1802; Robert Hooper, A Compendious Medical Dictionary, Boston, 1801; The Philadelphia Medical Dictionary, Phila., 1808). Typhus causes a rapidly rising fever that peaks at 102 to 105 degrees during the first two or three days and is then sustained for another five. In the course of the fever the patient experiences delirium and, on or about the fifth day, a dark red rash of elevated spots appears. Thereafter the fever falls rapidly, assuming that the outcome is favorable (Cambridge World History of Human Disease, ed. Kenneth F. Kiple, N.Y., 1993, p. 1080–1081). The use of Peruvian bark would have reflected contemporary medical practice for typhus, because while quinine was used for malarial fevers, it was used also “for most patients who had been debilitated by continued fevers” (J. Worth Estes, Dictionary of Protopharmacology, Therapeutic Practices, 1700–1850, Canton, Mass., 1990, p. 48). These are approximately the symptoms and the treatment JA described in his letters, particularly those of 9 Oct. to his wife (Adams Family Correspondence description begins Adams Family Correspondence, ed. L. H. Butterfield and others, Cambridge, 1963– . description ends , 4:224), and 15 Oct. to the president of Congress (Wharton, ed., Dipl. Corr. Amer. Rev. description begins Francis Wharton, ed., The Revolutionary Diplomatic Correspondence of the United States, Washington, 1889; 6 vols. description ends , 4:776–779).

A diagnosis of typhus is intriguing, but no less speculative than others that have been proposed. Ultimately all that can be said is that JA had a serious, debilitating illness in 1781 that severely curtailed his activities for months. Its precise nature is unknown.