NEW YORK — The governors of New York and New Jersey are at odds with scientists over Ebola as they back 21-day quarantines for medical workers returning from West Africa, while the nation’s top infectious-disease expert warns that such restrictions are unnecessary and could discourage volunteers from aiding disease-ravaged countries.

The two governors late Sunday night emphasized separately that their policies permit home confinement for medical workers who have had contact with Ebola patients if the workers show no symptoms. They will receive twice-daily monitoring from health officials.

The emphasis on home confinement was at odds with the widely criticized treatment of a nurse returning from Sierra Leone who was forcibly quarantined is a New Jersey hospital isolation unit even though she said had no symptoms and tested negative for Ebola.

New York Gov. Andrew Cuomo said such quarantines in medical facilities would only be used in some cases, such as if the health care workers were from states other than New York or New Jersey. For workers under home confinement, family members will be allowed to stay, and friends may visit with the approval of health officials. Workers displaying any symptoms will go straight to the hospital.

“We’re staying one step ahead,” Cuomo said Sunday night. “We’re doing everything possible. Some people say we’re being too cautious. I’ll take that criticism.”