This hospital cost $52 million. It treated 79 virus patients.

The Queens Hospital Center emergency department has a capacity of 60, but on its worst night of the coronavirus pandemic, more than 180 patients lay on stretchers in the observation bays and hallways. Alarms rang incessantly as exhausted doctors rushed from crisis to crisis.

Less than four miles away, a temporary hospital opened the next morning, on April 10. The facility, which was built at the U.S.T.A. Billie Jean King National Tennis Center to relieve the city’s overwhelmed hospitals, had hundreds of beds and scores of medical professionals trained to treat virus patients.

But in the entire month that the site remained open, it treated just three patients from the Queens Hospital Center emergency department, records show. Over all, the field hospital cost more than $52 million and served only 79 patients.