As he sits in Geneva, Michel Dreifuss does not feel all that far away from the Hamas attack on Israel on October 7 and the subsequent war at Gaza. The ripples are rolling through Europe and upending assumptions both global and intimate — including those about his personal safety as a Jew.

“Yesterday I bought a tear-gas spray canister at a military-equipment surplus store,” the 64-year-old retired tech sector worker said recently at a rally to mark a month since the Hamas killings. The choice, he says, is a “precaution,” driven by a surge of antisemitism in Europe.

Last month’s slayings of more than 1,400 people in Israel by Palestinian terrorists represented the biggest killing of Jews since the Holocaust. The fallout from it, and from Israel’s military response has extended to Europe. In doing so, it has shaken a continent all too familiar with deadly anti-Jewish hatred for centuries.

The past century is of particular note, of course. Concern about rising antisemitism in Europe is fueled in part by what happened to Jews before and during World War II, and that makes it particularly fearsome for those who may be only one or two generations removed from people who were the victims of riots against Jews and Nazi brutality.

What most chills many Jews is what they see as the lack of empathy for the Israelis killed during the early morning massacre and for the relatives of the hostages — at least 30 of whom are children — suspended in an agonizing limbo.

“What really upsets me,” Holocaust survivor Herbert Traube said at a Paris event commemorating the 85th anniversary of Kristallnacht, the 1938 government-backed pogroms against Jews in Germany and Austria, “is to see that there isn’t a massive popular reaction against this.”

The list of examples of anti-Jewish sentiment since the October 7 attacks is long and documented by governments and watchdog groups across Europe.

—Little more than a month after the attack in Israel, the French Interior Ministry said 1,247 antisemitic incidents had been reported since October 7, nearly three times the total for all of 2022.

—Denmark’s main Jewish association said cases were up 24 times from the average of the last nine months.

—The Community Security Trust, which tracks antisemitic incidents in Britain, reported more than 1,000 such events — the most ever recorded for a 28-day period.

That all comes despite widespread denunciations of anti-Jewish hatred — and support for Israel — from leaders in Europe since the attack.

Some of Europe’s Jews say they see it on the streets and the news. Jewish schoolchildren face bullying on their way to class, or — in one instance — have been asked to explain Israel’s actions, according to Britain’s Community Security Trust. There’s been talk of blending in better: covering skullcaps in public and perhaps hiding mezuzahs, the traditional symbol on doorposts of Jewish homes.

In Russia, a riot broke out at an airport in which there were some antisemitic chants and posters from a crowd of men looking for passengers who had arrived from Israel. A Berlin synagogue was firebombed. An assailant stabbed a Jewish woman twice in the stomach at her home in Lyon, France, according to her lawyer.

In Prague’s Little Quarter last month, staffers at the well-known Hippopotamus bar refused to serve beer to several tourists from Israel and their Czech guides, and some patrons served up insults. Police had to step in. In Berlin, Jews are still reeling from an attempted firebombing of a synagogue last month.

“Some of us are in a state of panic,” said Anna Segal, 37, the manager of the Kahal Adass Jisroel in Berlin, a community of 450 members.

Some community members are changing how they live, Ms. Segal said. Students no longer wear uniforms. Kindergarten classes don’t leave the building for field trips or the playground next door. Some members no longer call taxis, or they hesitate to order deliveries to their homes. Hebrew-speaking in public is fading. Some wonder if they should move to Israel.

“I hear more and more from people from the Jewish community who say they feel safer and more comfortable in Israel now than in Germany, despite the war and all the rockets,” Ms. Segal said. “Because they don’t have to hide there.”