The condition of Dr. Craig Spencer, the New York City physician being treated for the Ebola virus at Bellevue Hospital Center in Manhattan, has improved, hospital officials said Saturday morning.

Spencer, 33, of West Harlem, is considered in "stable" condition -- an upgrade from his previous "serious but stable" condition, NYC Health and Hospitals Corporation announced.

"Based on our patient's clinical progress and response to treatment, today HHC is updating his condition to 'stable' from 'serious but stable,' " hospital officials said in a news release. "The patient will remain in isolation and continue to receive full treatment."

No further information on Spencer's response to treatment or his outlook was immediately available, officials said.

Spencer worked in Guinea as a volunteer for Doctors Without Borders to fight the Ebola virus, which has killed nearly 5,000 people in West Africa.

He left Guinea on Oct. 14 and landed at Kennedy Airport on Oct. 17.

Spencer reported developing a fever on Oct. 23 and was admitted to Bellevue -- one of 10 New York hospitals tapped by state officials to treat suspected cases of Ebola. Other hospitals ready to care for Ebola patients include the North Shore-Long Island Jewish Health System and Stony Brook University Hospital on Long Island.