NILIN, West Bank — Jalal Zuhair Mansour supports his wife and four children on the $2,800 a month he is paid as a maintenance man for a Tel Aviv housing complex. But on Tuesday, after a few weeks in an apartment his boss lent him because of an Israeli ban on commuting from the West Bank, he called it quits and journeyed home to Beitunia, on the outskirts of Ramallah.

The coronavirus was simply too widespread where he worked to take any chances, he said, adding: “I am not ready to lose myself and my family.”

Mr. Mansour, and thousands of others like him, have suddenly become the Palestinian Authority’s worst nightmare.

Outbreaks at two kosher chicken slaughterhouses on the Israeli side sickened dozens of Palestinian workers, who brought the virus back to their hometowns. Palestinian officials now say that returning workers are responsible for at least a third of the known cases on the West Bank, including its only death.