The president’s statements seemed outlandish. Aides suggested his mood had changed. Secret sources revealed to the press that the illness was worse than had been publicly recognized.

This did not happen last week. It took place in October 1919, when President Woodrow Wilson suffered a debilitating stroke and people around him attempted to conceal the severity of the illness. His wife, Edith, operated as gatekeeper, carefully deciding what details would be publicly released and what would be protected.

While there are enormous differences and 101 years between 1919 and 2020, historical precedents make one thing crystal clear: public presidential illnesses can be a turning point that shape the public’s view of the president. This is especially important during an election year, when a debilitating illness may reflect poorly on the president’s ability to achieve his ends — even if it prompts a substantial upwelling of sympathy, thoughts and prayers.

President Trump’s illness with covid-19, the disease caused by the novel coronavirus, served as a reminder that the health of the nation’s president matters — not only for the individual, but for shaping public opinion and for the efficiency of policymaking. Wilson’s 1919 stroke revealed the significant role health plays in one’s ability to lead and maintain public trust.

Other than in 1881, when President James Garfield hung on to life for 2 ½ months after an assassination attempt, Wilson became the most severely ill president to continue to hold the office. He did so for almost a year and a half after his stroke. Like Trump, his illness came amid a deadly viral pandemic.

Indeed, historians believe but cannot prove definitively that Wilson’s negotiations after World War I at the Paris Peace Conference in April 1919 were interrupted by a case of the flu, or symptoms closely approximating it, that required him to stay in bed and cease most work for several days. If what he suffered was the flu, or pneumonia and an infection, as some speculate based on doctor’s notes and contemporary accounts, Wilson’s stroke in the fall of 1919 may well have been precipitated by this illness earlier in the year.

Records make clear the president’s mind was jumbled. He was paranoid in Paris. He often worried about being surrounded by spies. The president’s doctor, Rear Adm. Cary Grayson, seemed clear in private letters that Wilson was “sick with the influenza” in Paris and he lamented that this bout came just as “the whole of civilization seemed to be in the balance.”