The situation in New Rochelle — to say nothing of the Hasidic communities in Brooklyn, where as of Tuesday some yeshivas still remained open — is a case study in how religious communities are particularly vulnerable, especially religious communities that send their children to parochial schools and gather three times a day for communal prayer.

Dr. Steven Shayani, a cardiologist at the Icahn School of Medicine at Mount Sinai who was raised in Great Neck, thinks that his hometown is going to be hit hard in part because the village and its surrounding region have “double, maybe even triple” the number of synagogues as New Rochelle. “When I realized that 10 days ago,” he told me, “I got on the phone and called every local official. If New Rochelle has that many cases, imagine what Great Neck will be.”

What he learned, talking to health and school officials, was that “there is nobody in charge.” The “chain of command is broken in New York state,” he said. So instead of relying on officials, Dr. Shayani took the initiative to warn the community himself, reaching out and asking his contacts to practice rigorous social distancing. But he knows his influence is limited: “I’m one doctor sending texts and emails.”

Mayor Bral has told all Great Neck citizens to stop gathering together, including to worship. Crucially, his order went into effect before the Sabbath, a time when families typically get together in synagogues and for meals.

Rabbis followed his lead and urged their congregants to stay home. Yosef Bitton, the rabbi of the United Mashadi Jewish Community in Great Neck, wrote in a note to his community, “This is a very special Shabbat for me because this Sunday is the anniversary of my father.” Every year on the anniversary of his father’s death Rabbi Bitton says Kaddish, the mourner’s prayer. “But I know as a rabbi,” he wrote, “that protecting your life and avoiding the risk of someone else’s life, is more important than saying Kaddish.”

Still, after Shabbat ended, rumors spread of people holding services in homes and synagogue parking lots. Mayor Bral took to Facebook to admonish them: “Stern warning for those individuals who held services in their home for Shabbat, you have put many people’s lives in danger. Don’t be selfish!”