Call it the Legionnaire's Disease of 1857:
"One painful incident, however, cast a cloud over the opening of the new [Buchanan] Administration. Guests at one of the principal hotels were seized with sudden and alarming symptoms of disease, of which the nature and cause were unknown. Some died, many lingered long on beds of sickness, and could only be carried to their homes after weeks of suffering. None were exempt. Transient visitors, and habitues, Democrats, Republicans, and 'Americans,' Senators, Congressmen, and Judges, military and naval officers, and even the new President were attacked with more or less violence, by the 'National Hotel disease.' Physicians pronounced it to be poisoning, and there were various theories as to its origin. Some attributed it to criminal malice; others to leaden water-pipes and defective drainage. It was a pestilence that soon cleared the hotel of occupants; and the apprehensions it excited led many people to quit the city." *Autobiography of William H. Seward*, p. 298.
http://books.google.com/books?id=SqQdj_QiOmAC&pg=PA298
"The Mysterious National Hotel Disease
June 24, 1859
On this date, David F. Robison of Pennsylvania died at his Chambersburg, Pennsylvania, home of complications from the mysterious National Hotel Disease, contracted more than two years earlier at the time of President James Buchanan's inauguration. By some accounts, nearly three dozen people died from the affliction and as many as 400 more were sickened. The National (located on the site of the present-day Newseum) was one of the city's most popular and plush hotels, serving a clientele of influential politicians, particularly southern Members of Congress. Buchanan, a former Representative from Pennsylvania once described as a 'northern man with southern principles' and possessing anti-abolitionist convictions, chose the National as his pre-inauguration lodgings. The President-elect and several Members of the Pennsylvania delegation--including Robison, set to retire from Congress of March 3--were among the scores of hotel guests who fell ill (though Buchanan made a quick recovery). Rumors, fed by sensationalized newspaper coverage, soon emerged that victims had been poisoned by arsenic, the result of a botched assassination attempt on Buchanan by radical abolitionists. 'From every quarter of the country come in denunciations of what is styled--not without warrant,' blared the New York Times, 'the determination on the part of interested parties to stifle inquiry and hoodwink suspicion concerning what has every appearance of being the most gigantic and startling crime of the age.' Medical experts now believe the disease outbreak to have been caused by dysentery because of the hotel's primitive sewage system. In an age when scientists and doctors knew little about bacterial infections and how to treat them, dysentery was a dangerous affliction. The National Hotel Disease claimed two other victims in the House--John G. Montgomery of Pennsylvania, who lingered until April 1857, and John Quitman of Mississippi who died the following summer from after-effects."
http://history.house.gov/HistoricalHighlight/Detail/36247?ret=True
"Thursday, March 5 [1863]. At lunch to-day I had a talk with Mr. Forbes. He said he had very good reasons for saying that the famous disease at the National Hotel, in Washington, in 1857, from which so many persons suffered, was the result of an attempt on the part of the Southern disunionists to poison Buchanan, in order to bring in Breckinridge as President, who was in their councils, and would throw the power of the Government into their scale. He said that soon after he visited a prominent Southern politician, living at Culpepper Court House, in Virginia, and that from what there transpired he was convinced he was in the plot. He did not mention his name, and I did not think it proper to ask it." Henry J. Raymond, editor of the *New York Times,* private journal, published in *Scribner's Monthly* in 1880.
http://books.google.com/books?id=_7TPAAAAMAAJ&pg=PA710
"...[After staying in Washington from Januray 27 to February 3, 1857] Buchanan returned home [to Wheatland] a sick man, one of the victims of the so-called National Hotel disease which afflicted guests and employees at the time of his stay. There were various explanations for it. Some traced it to the water taken from the hotel cistern, into which rats poisoned with arsenic had fallen. Others attributed it to a poisonous miasma rising from the hotel's sewers, cesspools, and sinks. The most likely cause was the contamination of both food and water by a sewage back up resulting from frozen plumbing during the bitter cold of late January. The disease itself was probably paratyphoid fever. The symptoms were severe and persistent diarrhea and inflamation of the colon, effective treatment for which was then unknown to the medical profession. On February 25, after Buchanan had endured several weeks of misery, the public was informed that visitors would no longer be received at Wheatland before the inauguration." Kenneth M. Stampp, *America in 1857: A Nation on the Brink,* p. 60.
http://books.google.com/books?id=Q5WF8NCK9YYC&pg=PA60
***
The above quotes should give you some idea of the severity of the "National Hotel Disease," and incidentally of its capacity for arousing competing conspiracy theories (abolitionists out to kill the doughface Buchanan? southern disunionists out to make Breckinridge president?). Naturally, it gives rise to all sorts of what-ifs:
(1) The most obvious: What if the disease kills Buchanan and makes Breckinidge president? How does his administration differ from Buchanan's?
Breckinridge eventually earned a reputation for pro-slavery extremism because some of the people who supported him for the presidency against Douglas in 1860 were secessionists, and because he eventually became a Confederate general and later Secretary of War (the best Secretary of War the Confederacy had, btw--but appointed way too late to make any difference). Actually, for a long time he was a relative moderate among Southern Democrats. He even (unlike Buchanan) urged Douglas' re-election to the Senate in 1858--much as he disagreed with the Senator about Lecompton and the "Freeport Doctrine" he thought him far preferable to Lincoln. Again, there is some evidence that when he accepted the anti-Douglas Democrats' nomination in 1860, he did so in the expectation that this would get Douglas to withdraw so that a compromise candidate could be named. (Breckinridge's biographer William C. Davis in any event thinks there is "little doubt that his acceptance was a stratagem to bring about Douglas' withdrawal."
https://books.google.com/books?id=mbAfBgAAQBAJ&pg=PA226) Breckinridge had the support of extremists like Yancey, but was not really one of them.
Nevertheless, even if President Breckinridge were to be more conciliatory to Douglas than Buchanan was, the gap between Southern and Northern Democrats was by 1860 probably too wide to bridge. So let's say that the Democrats split anyway, and Lincoln (or another Republican) gets elected--or for that matter, that even if a Democratic split is avoided, Lincoln gets elected anyway. The Deep South prepares to secede. Now comes what I think will be a major difference between Buchanan and Breckinridge--though Breckinridge too will urge the Union be preserved by concessions to the South, once the states start to secede, he will regard their action as legal and will surrender all federal property, *including Fort Sumter.* Furthermore, he will recognize the CSA. (After all, the Constitution gives the President the right "to receive Ambassadors and other public Ministers.") These measures will provoke cries for his impeachment, but I doubt that the Republicans, even if joined by some Douglas Democrats, would have the votes in the Senate to remove him, as long as the Upper South stays in the Union for a while.
This will present Lincoln with a much worse situation than in OTL. "De-recognizing" the Confederacy and attempting to regain forts already taken will be opposed by a lot more Northerners (and border state residents) than simply sending an expedition to provision a fort still in Union hands.
(2) According to Stampp, Douglas was one of the people who "called on the President-elect at the National Hotel." (Buchanan congratulated Douglas on his improved appearance since his marriage. Douglas suggested--I'm not sure how seriously--that Buchanan try the same remedy himself.) Even if they only had a meal or even only some iced drinks together, that could be enough to give Douglas the disease. So suppose Buchanan lives--but Douglas dies? As I have noted elsewhere,
http://groups.google.com/group/soc.history.what-if/msg/4db8db990ccfc77c without Douglas it is plausible that the Lecompton Constitution will pass Congress, and Kansas will be admitted as a slave state. This could result in a return of violence there. OTOH, if Kansas remains peaceful, the Democrats might have improved prospects for 1860, because Douglas was a very divisive figure in the Democracy.
(3) I'm sure there are all sorts of other politicians who theoretically could have died of the disease (even if they were not in fact at the National Hotel at the time, they could have been in an ATL). What if outgoing Secretary of War Jefferson Davis, who has recently been elected US Senator from Mississippi, pays his respects to Buchanan at the Hotel, and falls ill and dies? Assuming secession still comes, who will be President of the Confederacy?
(4) So far the what-ifs have involved the disease killing more people than it did in OTL. But what if there had been no outbreak at all of the disease? What for example would have been the role of John Quitman
http://en.wikipedia.org/wiki/John_A._Quitman in the Confederacy?
Also, is it possible that the disease had some lasting effect on Buchanan? (It killed his secretary, Harriet Lane's brother Elliot Lane.) James Ford Rhodes in his *History of the United States from the Compromise of 1850* wrote that the disease "was the beginning of his physical disability."
http://books.google.com/books?id=YgXVAAAAMAAJ&pg=PA205 For another account, there was an article in *The Grog Ration* ("A Bi-Monthly Digest of Navy Medical History") which alas is apparently no longer available on the Web:
"Buchanan did not fully recover from his initial bout with National Hotel Disease despite resting at Wheatland. A letter to Buchanan in Lancaster from [Navy Surgeon] Foltz in Philadelphia (February 23, 1857) expressed pleasure at his recovery, but prescribed: 'if there is any mineral poison in your system, the best means to eradicate it is, to supply the system freely with protine (sic) -- i.e. --eat beef, mutton & all nutritious animal foods, avoiding vegetables and acids.' The same letter warned against a return to the previous venue: 'If you have not engaged rooms elsewhere, you should do so by all means. The water near the President(s) House all comes from the same spring and is the best in the city.'
"Subsequently, Buchanan summoned Foltz from Philadelphia after suffering a relapse. The politician accepted his physician's medical care, but not his advice. Buchanan, somewhat recovered, returned with his doctor to the National Hotel in anticipation of his inauguration. We must return once again to Foltz's diary for his narrative: On Inauguration Day, disease broke out again with increased violence; four hundred were ill. More than forty died 'with strong symptoms of having taken some mineral poison.' Buchanan insisted that Foltz remain with him and installed him in the White House, in a room adjacent to the new president's. Buchanan recovered so slowly that he requested that the Secretary of the Navy extend Navy Surgeon Foltz's leave of absence. The specifics of his treatment are unknown other than Foltz, in a letter to his wife, 'Tries to keep Buchanan from crowds who would kill him.' *The subsequent course and consequences, if any, of National Hotel Disease upon James Buchanan, are unrecorded.*" (My emphasis.)
It is tempting to think that a more physically vigorous Buchanan might have stood up more to southern pressure, and handled the secession crisis better. But even assumng that the disease had some long-term impact on Buchanan's health, my impression of the Buchanan administration is that he was vigorous enough--he was just vigorous in pursuit of some very bad policies (e.g., Lecompton). Stampp IMO rightly rejects Nevins' portrayal of Buchanan as a weak man dominated by a southern cabal: "The conclusion seems warranted that Buchanan's policy, while pleasing to most Southerners, was nevertheless *his* policy, not one forced upon him by others." (p. 285) And one also cannot say that Buchanan's Lecompton decision was a sign of Buchanan's inability to resist pressure; after all, there was plenty of pressure on him by *northern* Democrats to stand by his commitment to full submission of the constitution to the Kansas voters. (p. 284)