NBC News - Doctors and other health care workers coming back from treating Ebola patients in West Africa will have to sit out a mandatory 21-day quarantine in New York and New Jersey, the states' governors said Friday.

New York Gov. Andrew Cuomo and a New Jersey Gov. Chris Christie said they were adding screening protocols for Ebola at both JFK and Newark airports.

They said the case of Dr. Craig Spencer, hospitalized Thursday night with Ebola, showed the need to force anyone who had contact with an Ebola patient to stay home. State health officials are tracking Spencer's movements after learning he'd ridden public transport and visited a busy bowling alley.

On Friday, a staffer of Medecins Sans Frontieres (Doctors Without Borders) who had been treating Ebola patients in West Africa was quarantined after arriving at Newark Airport. The New Jersey Department of Health said the worker showed no symptoms initially but developed a fever Friday evening and was isolated at University Hospital in Newark.

Health experts stress that people are not contagious until they start showing clear symptoms of Ebola, and officials say they are cleaning the bowling alley out of an abundance of caution. And doctors who have volunteered in West Africa say the move will backfire because health workers won't want to — or won't be able to — travel the West Africa to help fight the epidemic there.

Federal officials had already announced plans to force monitoring of anyone coming into the U.S. from an Ebola-affected country.

“There will also be a mandatory quarantine for any individual who had direct contact with an individual infected with the Ebola virus while in one of the three West African nations (Liberia, Sierra Leone or Guinea), including any medical personnel having performed medical services to individuals infected with the Ebola virus,” Christie and Cuomo said in a joint statement.

“Additionally, all individuals with travel history to the affected regions of West Africa, with no direct contact with an infected person, will be actively monitored by public health officials and, if necessary, quarantined, depending on the facts and circumstances of their particular situation.”

Ebola survivor Dr. Rick Sacra says it's not necessary. “People who are not ill, who don't have a fever, who are not clinically ill, cannot spread Ebola,” he told Andrea Mitchell on MSNBC. And he said he feared such quarantines might discourage volunteers from going to help fight the epidemic, which has infected 10,000 people and killed half or more of them.

“We need to find ways to encourage more people to go and not make the situation too burdensome for them on their return,” Sacra said.

Dr. Nicole Lurie, a top preparedness official in the Health and Human Services Department, echoed these doubts about mandatory quarantines at a meeting of the House Oversight and Government Reform Committee. She said Spencer took the proper actions in taking his temperature and reporting his fever promptly. He followed protocols written by Medecins Sans Frontieres, the group he was working with in Guinea.

“From what we understand, people are infectious when they have a fever, not beforehand,” she said.

“We really want to move in an abundance of caution,” Lurie added. “The bowling alley is closed so that it can be cleaned and decontaminated out of an abundance of caution.”

Centers for Disease Control and Prevention spokesman Tom Skinner says the agency will consider any measures necessary to reassure Americans that they are protected from an Ebola epidemic.

“There are lots of options being discussed,” Skinner said by email. “We want to strike the right balance of doing what is best to protect the public's health while not impeding whatsoever our ability to combat the epidemic in West Africa. Our risk here will not be zero until we stop the epidemic there.”