Yardley Wong, captive on the Japanese cruise ship grappling with the coronavirus, captured in a single image the essence of life under quarantine. From inside her tiny cabin, Ms. Wong took a picture of the closed doorway. She posted it to Twitter last week.

“So much wondering through this door,” she wrote.

From the Black Plague to the flu pandemic of 1918 to more recent outbreaks, the history of quarantine and medical isolation shows common emotional threads of those on both sides of such doors — uncertainty, terror, loneliness, separation. But this time, the raw physical barrier is showing cracks, thanks to the smartphone.

“After some emotional breakdown, I find my peace from you all,” Ms. Wong tweeted several days after her post brought messages of support from people around the world. “Thank you for the kindness. Your tweets give me strength.”