I was right abut the Swamp Gas

Death in the White House: President William Henry Harrison's Atypical Pneumonia.

Historians have long maintained that pneumonia killed William Henry Harrison (1773-1841) just 1 month after he became the ninth president of the United States. For more than a century and a half, it has been alleged that the aged Harrison caught a fatal chill the day he was sworn into office while delivering an overly long inaugural address in wet, freezing weather without a hat, overcoat, and gloves. However, a careful review of the detailed case summary written by his personal physician suggests that enteric fever, not pneumonia per se, was the disorder that carried off "Old Tippecanoe." Two other presidents of that era, James Knox Polk and Zachary Taylor, also developed severe gastroenteritis while in office. Taylor's illness, like Harrison's, proved fatal. In all 3 cases, the illnesses were likely a consequence of the unsanitary conditions that existed in the nation's capital during most of the nineteenth century.

I always joked that they need to check for Swamp gas in DC.