The Mount Sinai health network has 76 patients with the coronavirus at its hospitals in Brooklyn, Queens and East Harlem—a "small but noticeable increase," according to a spokesperson. The Northwell network is also seeing an uptick.

Dr. David Battinelli, Northwell's chief medical officer, says there's a 10-to-20 percent increase in cases, with most of them coming from Brooklyn and Queens. 

"For the first time in a while, we're getting double digit new cases a day," he said. "We were in the very low single digits."

Covid hospitalizations tend to lag behind increased case numbers, because most people who get sick weather the illness at home. Those who do go to the E.R. usually do so after several days of acute symptoms. Other hospital systems, like NYU and New York Presbyterian, say they haven't seen any increase.

An emergency room doctor at Maimonides Hospital in Borough Park says the increase there has been very modest, but they're bracing for more cases after the recent holidays, and as the weather gets colder and people spend more time inside. 

The New York City Health and Hospitals Corporation, the country's largest municipal hospital system, declined to comment.