68-year-old US president who served shortest term died from suspected pneumonia

U.S. presidents generally spend years in office, but the ninth president of the United States served only for a month.

William Henry Harrison holds the record for serving the shortest term thus far after he died on April 4, 1841, just 30 days after taking over the White House.

Experts had long attributed his unexpected demise to pneumonia. As the Miller Center notes, "During the address, the new president wore no coat or hat. As a soldier, farmer, and outdoorsman, Harrison had spent much of his life in bad weather. But he was far from young now, and when he followed the address with a round of receptions in his wet clothing, it resulted in a bad chill. Within days, he had a cold, which developed into pneumonia."

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Harrison's personal doctor Thomas Miller reportedly wrote that he had "...pneumonia of the lower lobe of the right lung, complicated by congestion of the liver."

However, some researchers argued in a 2014 study that the real cause was likely enteric fever due to "the unsanitary conditions that existed in the nation's capital during most of the 19th century."

In addition to a lack of a sewer system at the time, they point out that the inauguration weather wasn't that extreme, and thepresident's gastric issues made him susceptible to enteric fever.