The call came on March 24. Bob McGuire, the executive director of CP Nassau, a nonprofit group that cares for the developmentally disabled, received a report from a four-story, colonnaded building in Bayville, N.Y., that houses several dozen residents with severe disabilities ranging from cerebral palsy to autism. For many of them, discussions of social distancing or hand washing are moot.

“Bob, we’re starting to see symptoms,” Mr. McGuire was told.

Fevers were spreading. Within 24 hours, 10 residents were taken to the hospital. Now, little more than two weeks later, 37 of the home’s 46 residents have tested positive for the coronavirus. Two are dead; nine remain hospitalized. At least eight members of the staff have tested positive as well.

“Forgive me if I get emotional,” Mr. McGuire said in an interview, choking up. “People discount people with disabilities and presume they understand them when they don’t know them. They think their lives are not worth the same as yours or mine, and that’s just not true.”

As the coronavirus preys on the most vulnerable, it is taking root in New York’s sprawling network of group homes for people with special needs.