Clutching a gray plastic suitcase filled with most of his belongings — a blanket, a toothbrush, a pair of white sneakers and a comb — Wang Sheng goes from factory to factory in southern China begging for a job. The answer is always no.

Mr. Wang, 49, used to be able to find work in Shenzhen, a sprawling industrial megacity. But factories are turning him away because he is from Hubei Province, the center of China’s coronavirus epidemic, even though he hasn’t lived there in years.