One got out of Nazi Germany on a Kindertransport train to Sweden, never again seeing his parents, who were exterminated in the death camps. One survived two notorious concentration camps, Auschwitz and Bergen-Belsen, and was discovered by British troops on a pile of bodies, half-dead with typhus. One endured freezing temperatures and near starvation in a slave-labor camp in Siberia.

David Toren, Faye Becher and Joseph Feingold survived the Holocaust, bearing witness to the seismic events of the last century. Last month, all three died by the same tiny microorganism, isolated once more from their family members. Mr. Toren, who spent his late years fighting to recover paintings looted by the Nazis, was 94; Ms. Becher, matriarch of a close Brooklyn family, was 95; Mr. Feingold, who was the subject of the 2017 Oscar-nominated documentary short “Joe’s Violin,” about his gift to a young Bronx girl, was 97.

The New York area is home to just under 40,000 Holocaust survivors, down from nearly twice that many in 2011, according to Selfhelp Community Services, which serves Nazi victims. Now those survivors, mostly in their 80s and 90s, face a new menace that targets people like them: In New York State, the coronavirus has killed more than twice as many people age 80 and up as it has people under 60.

“This pandemic is the greatest threat to this generation since the Second World War,” said Stephen D. Smith, executive director of the USC Shoah Foundation, which interviews survivors of genocide. Many are only now telling their stories in full, he said.