William Henry Harrison at 68 was the oldest man ever elected U.S. president when he won the office in 1840. He held that distinction until Ronald Reagan was elected almost a century and a half later.

But Harrison's time in office – just 31 days – is still the shortest presidency ever. And he was the first U.S. president to die in office.

Born and raised in Virginia, Harrison came to Philadelphia to study medicine at the University of Pennsylvania. But when his father died and he had no money to continue his studies, Harrison dropped out in 1791 to join the new nation's army. He was sent to the Northwest Territory, where he fought in the Northwest Indian Wars. He went on to serve first as a delegate to Congress and then as governor of the Indiana Territory.

In 1811, he became the hero of the Battle of Tippecanoe against Tecumseh and the Shawnee, and later held a number of important political posts. But his hero status would provide him with one of the most famous presidential campaign slogans ever when he ran for president in 1840, as a member of the Whig party, with John Tyler as running mate: "Tippecanoe and Tyler Too."

To fight rumors that he was too old and ill to serve as president, he waged a very active campaign that left him exhausted. Although March 4, the day of his inauguration, was bitterly cold with rain and snow, Harrison rode on horseback to the ceremony rather than in the closed carriage that had been offered to him.

The new president stood without an overcoat and hat to deliver the longest inaugural address in American history. It took him nearly two hours to read the 8,445-word speech. Harrison then rode through the frigid Washington streets in the inaugural parade, and that evening attended three inaugural balls, including the "Tippecanoe" ball, attracting 1,000 guests.

Two weeks later, Harrison, weakened from a lingering chest cold, took an early-morning walk and got caught in a rainstorm. He developed what his doctor diagnosed as pneumonia.

Harrison's physician bled and purged him, as was the custom, but without benefit. Harrison died April 4, 1841.

History long has accepted the doctor's verdict that being out in the inclement weather led to Harrison's fatal illness. But why did it develop so long after the inauguration?

Solution:

Nine years after Harrison's death, the White House water supply was found to be contaminated with sewage that flowed into a marsh a short distance away.  Deadly bacteria could thrive in such an environment, including the salmonella bacteria that cause typhoid and paratyphoid fever.

Classic typhoid fever is a communicable disease with symptoms of intestinal inflammation, fever, headache, abdominal pain, severe weakness, and either constipation or diarrhea, caused by the bacteria Salmonella typhi. A rash called rose spots may also be noted on the abdomen.

Typhoid fever typically spreads through contaminated food and water or through close contact with an infected person. Signs and symptoms develop gradually, often appearing one to three weeks after exposure.

Harrison's symptoms and the fact his illness developed two to three weeks after entering the White House, point to a diagnosis other than pneumonia, most likely typhoid fever.

In the pre-sewer days of D.C., two other presidents — James Polk and Zachary Taylor — also fell ill with so-called stomach bugs, likely typhoid or another type of enteric fever, during their time in the White House, but both survived. President Abraham Lincoln's 11-year-old son, Willie, died of typhoid fever in the White House during the Civil War.

Today, the typhoid vaccine has made this condition virtually unheard of, though fecal bacteria can still cause devastating illness and remain the world's second leading cause of death for children under age 5.

Allan B. Schwartz, M.D., is a professor of medicine in the Division of Nephrology & Hypertension at Drexel University College of Medicine.