Frida Ghitis, a former CNN producer and correspondent, is a world affairs columnist. She is a frequent opinion contributor to CNN, a contributing columnist to the Washington Post and a columnist for World Politics Review. Follow her on Twitter @fridaghitis. The opinions expressed in this commentary are those of the author. Read more opinion on CNN.

(CNN) On Saturday night, the seventh night of Hannukah, a man entered the home of a rabbi in Monsey, New York, pulled out a machete, and started stabbing worshippers celebrating the Jewish festival of lights. It was at least the ninth attack against Jews in just over a week in the New York area. He was later arrested back in New York City, reportedly covered in blood.

Frida Ghitis

If you think this is a New York problem, or a Jewish problem -- or perhaps a far-right, or a far-left, or a black or white problem -- you should think again.

History has engraved a lesson about anti-Semitism for all humanity. Anti-Semitism is a symptom of a larger societal problem. Sure, when Jews are unsafe, it is they who are most at risk, but Jews are the canary in the coalmine, an early warning sign of a community or a nation losing its moorings.

The coalmine is filling with toxic fumes.

Soon we will learn more about the alleged perpetrator, who has pleaded not guilty to five counts of attempted murder and one count of burglary. Federal prosecutors have charged him with hate crimes; in the filing of those charges, authorities report finding journals with references to Hitler and a drawing of a swastika and Star of David, as well as a phone used recently to search terms like "German Jewish temples near me" and "Zionist Temples in Elizabeth NJ." His family says he has a history of mental illness and "was raised in a home which embraced and respected all religions and races." Whatever his motivation, the rampage focused so brutally on Jews, making it part of a swelling tide of anti-Jewish violence rising across the world. In the US alone, according to the Anti-Defamation League, anti-Semitic attacks doubled last year.