Liz Szabo

USA TODAY

A New York doctor has recovered from Ebola and is scheduled to be released from the hospital Tuesday.

The New York City Health and Hospitals Corporation, which runs the city's public hospitals, said Monday in a written statement that physician Craig Spencer "has been declared free of the virus." Spencer, who treated Ebola patients in Guinea while working with Doctors Without Borders, "poses no public health risk," the statement said.

Spencer, 33, tested positive for the virus Oct. 23.

Spencer has been treated in a specially designed isolation unit at Manhattan's Bellevue Hospital. His condition was upgraded from serious to stable last week.

His fiancee and two friends were quarantined initially but were released and are being actively monitored.

Spencer's case touched off a firestorm of controversy when the governors of New York and New Jersey instituted quarantine orders for travelers from West Africa after learning that Spencer had taken the subway and gone bowling the night before he tested positive for the virus.

The alarm was unnecessary, experts said. Nearly four decades of experience with Ebola shows that the virus is not transmitted through casual contact and cannot spread until a patient has symptoms, says Amesh Adalja, senior associate at the Center for Health Security of the University of Pittsburgh Medical Center. An October report in The New England Journal of Medicine suggests that patients may not be contagious until two to three days after first showing symptoms.

Nearly three weeks after Spencer tested positive for the virus, no one else has become sick. He was the last person being treated for Ebola in this country.

Adalja said it's notable that the only two Americans to be infected with Ebola while in the USA have been medical workers caring for the first Ebola patient, Thomas Eric Duncan, who died in Dallas Oct. 8.

Ebola patients are not highly contagious in the early days of the illness, when levels of the virus in their blood are very low. They become more contagious as the illness progresses -- and as they develop heavy diarrhea and vomiting -- as the levels of virus in their blood rise. By this point, patients are usually hospitalized or bedridden, says Peter Hotez, dean of the National School of Tropical Medicine in Houston.

All eight Americans who have been treated for Ebola in U.S. hospitals have survived, a striking contrast to the 70% mortality rate in West Africa. The high survival rate in U.S. hospitals illustrates the value of aggressive care in an advanced intensive care unit, Adalja said.

Unlike doctors in West Africa, who sometimes lack access to running water and soap, doctors in the USA have a variety of ways to support patients with Ebola and manage serious side effects, such as low blood pressure and dehydration.

Beyond that supportive care, Spencer also received an experimental medication and a blood donation from Ebola survivor Nancy Writebol, a missionary who contracted the virus in Liberia and was treated at Emory University Hospital in Atlanta.

Contributing: Associated Press