His release 19 days later adds to the evidence that when treated in advanced American hospitals, Ebola has a lower fatality rate than in West African field hospitals starved of doctors, nurses and equipment.

The plan to release Dr. Spencer has not been publicly announced but was confirmed on Monday by two people familiar with his treatment, but who declined to be identified because they did not have permission to release the information. A spokeswoman for Bellevue did not immediately respond to a request for comment.

It was unclear Monday whether Dr. Spencer would return to his Hamilton Heights apartment, where his fiancée, Morgan Dixon, is under quarantine. Two friends who had contact with him in the days before his diagnosis were initially held in quarantine, but recently released.