The slum in El Salvador where María Graciela Barrera lives is dotted with white flags, outside homes, serving as distress signals that people inside don’t have enough food.

The coronavirus pandemic’s economic fallout thousands of miles away in the U.S. is hitting people like Ms. Barrera, 89, who is no longer getting the $50 a month that two of her grandchildren send from Los Angeles.

“Since they lost their construction jobs because of the coronavirus, we are adrift,” Ms. Barrera said one recent day after collecting a bag of basic goods distributed by a Catholic charity in San Salvador.