As of Friday, more than half of New York’s 613 licensed nursing homes had reported coronavirus infections, with 4,630 total positive cases and 1,439 deaths, officials said.

In New Jersey, nursing homes had been linked to 252 virus-related deaths, more than 90 of them in the past two days. The outbreak has now affected at least 70 percent of the state’s long-term care centers.

The actual infection rate in nursing homes is almost certainly higher than the data indicate because few homes have the capacity to test residents. The assumption among many in the industry is that every nursing home in the region has people with Covid-19.

The crisis in nursing homes is occurring in virus hot spots across the country, with infections growing in places like Rhode Island, Pennsylvania and North Carolina.

In New York, nursing home administrators said they had been overwhelmed by an outbreak that quickly spun beyond their control. They were unable, they said, to have residents tested to isolate the virus or to get protective equipment to keep workers from getting sick or transmitting the virus to residents.

“The story is not about whether there’s Covid-19 in the nursing homes,” said Scott LaRue, the chief executive of ArchCare, which operates five nursing homes in New York. “The story is, why aren’t they being treated with the same respect and the same resources that everyone else out there is? It’s ridiculous.”