My grandfather died of the flu virus. He was 31 years old — one of millions who perished during the global flu pandemic of 1918.

President Donald Trump wondered last month, "Does anybody die from the flu? I didn't know people died from the flu."

But his own grandfather did, like mine — in 1918.

Whether the president never knew or just forgot is unclear; he seems to not know a lot. For example, that the 1918 flu infected perhaps 500 million people, one third of the world's population at the time, and that somewhere between 50 million and 100 million died worldwide, more than in the two world wars combined.

Has Trump ever considered remembering the past and learning lessons from 1918 and the pandemic one science journalist called "the biggest disaster of the twentieth century"?

Does he know that at first some public officials dismissed the "Spanish" flu as seasonal, one that typically dies out in warm weather, nothing to be taken seriously? Or that it spread widely in the summer heat, then intensified in autumn, ultimately striking in three different waves?

He might be surprised to learn that some local governments downplayed the public risk. Philadelphia held a parade celebrating Liberty Bonds even as 600-plus soldiers and sailors stationed nearby lay seriously ill. Philadelphia's public health director assured citizens that it was just the normal flu and would be contained before infecting the civilian population.

So on Sept. 28, thousands of soldiers, Boy Scouts, marching bands and local dignitaries paraded through downtown Philadelphia as 200,000 spectators lined the streets. Days later, hospitals in the area filled with patients suffering and dying. Soon as many as 500 corpses awaited burial, some for more than a week. Cold-storage plants became temporary morgues.

Does the president remember that?

He might find it worthwhile to learn that St. Louis suffered flu-related deaths less than half the per capita rate of Philadelphia. How so? They banned large gatherings, staggered work shifts, limited streetcar ridership and encouraged wearing masks. Then, when some of the public pushed back against this "decision that infringes on people's rights," the mayor and city health officials held their ground.

Remember: Half the rate of death of Philadelphia.

Remembering the past might inform the president that history often repeats itself — or at least rhymes, as they say. In 1918, health care workers became endangered eyewitnesses to the contagion as one after another of their patients passed, unable to breathe, delirious, turning blue, suffocating to death.

One doctor described "bodies stacked like cords of wood in the hospitals."

Another witness: "The memory of this sight will haunt for life the minds of those who saw it."

Today our minds are haunted by fears of shortages, diminished incomes, even lost jobs. Serious concerns, no denying. But watching from the wrong side of a window as a family member slowly suffocates?

That's another matter. Lost profits and limited liberty? Or unlimited suffering and lost lives?

We're faced with lots of tough choices. We're told information from testing and tracing is crucial, so making the right choice may be all in the timing. But as we rush to liberate ourselves from temporary isolation, let's not forget: It's a choice that will alter lives forever.

An estimated 195,000 Americans died of influenza during one month, October 1918. Two who passed away days apart were Frederick Trump and Charles O. Moore — the president's grandfather and mine. Like many others who have lost loved ones to influenza, we are touched by their deaths even today.

One of them left his son a real estate business and fortune that found its way to the presidency. The other left his wife with three young children who soon found their way to a home for orphans. The president boasts of his wealth; my father claimed he was proud to be a "home kid."

I wonder who is yet to prosper, or suffer, or perish, especially if we fail to acknowledge the past before the virus touches us all.

Christopher O. Moore, of Belle Plaine, Minn., is a retired teacher.