NEW YORK/WASHINGTON (Reuters) - New York and New Jersey will automatically quarantine medical workers returning from Ebola-hit West African countries and the U.S. government is considering the same step after a doctor who treated patients in Guinea came back infected, officials said on Friday.

The steps announced by the two states, which go beyond the current restrictions being imposed by President Barack Obama’s administration on travelers from Liberia, Sierra Leone or Guinea, came as medical detectives tried to retrace the steps in New York City of Dr. Craig Spencer, who tested positive for Ebola on Thursday.

The new policy applies to medical workers returning from the region through John F. Kennedy International Airport in New York and Newark Liberty International Airport in New Jersey. In the first instance of the new move, a female healthcare worker who had treated patients in West Africa and arrived at the Newark, New Jersey, airport was ordered into quarantine.

“Voluntary quarantine is almost an oxymoron,” New York Governor Andrew Cuomo said. “We’ve seen what happens. ... You ride a subway. You ride a bus. You could infect hundreds and hundreds of people.”

Cuomo, who appeared at a news conference with the governor of neighboring New Jersey, Chris Christie, had earlier in the day sought to reassure New Yorkers that Ebola’s threat was limited the day after Spencer tested positive for the virus.

In Washington, Obama also sought to reassure a worried public with an Oval Office hug of Dallas nurse Nina Pham, who was declared Ebola-free on Friday after catching the virus from a Liberian patient who died.

As concerns over the possible spread of Ebola eased, U.S. stocks closed out their best week since January 2013. [.N]

But Republican lawmakers, many of whom for weeks have called for a tougher response to Ebola, continued their criticism of the administration at a congressional hearing.

Cuomo said the U.S. Centers for Disease Control and Prevention (CDC) had agreed that individual states have the right to exceed federal requirements.

A federal quarantine of healthcare workers returning to the United States from the three West African countries was one of a number of options being discussed by administration officials, Tom Skinner, a CDC spokesman, told Reuters.

Spencer, 33, who spent a month with the humanitarian group Doctors Without Borders in Guinea, was the fourth person diagnosed with the virus in the United States and the first in its largest city.

Dr. Mary Travis Bassett, New York’s health commissioner, said Spencer was awake and talking to family and friends by cellphone and was listed in stable condition in Bellevue Hospital’s isolation unit. Meanwhile, workers in biohazard gear began cleansing Spencer’s apartment in upper Manhattan.

The virus is not airborne but is spread through direct contact with bodily fluids from an infected person who is showing symptoms.

The Obama administration has implemented a series of steps aimed at preventing the further spread of Ebola in the United States but has stopped short of a travel ban on people from Liberia, Sierra Leone or Guinea called for by some politicians.

The United States is funneling travelers from those countries through five airports conducting special screening for signs of infection and is requiring them to report to health authorities for the 21-day Ebola virus incubation period. The airports include a New York City airport and a New Jersey airport that serve the metropolitan area.

“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,” Skinner said.

White House spokesman Josh Earnest declined to discuss the possibility of a nationwide quarantine policy but said “these kinds of policy decisions are going to be driven by science” and the advice of medical experts.

Slideshow ( 16 images )

NURSE RELEASED

Pham, one of two nurses from a Dallas hospital infected with Ebola after treating the first patient diagnosed with the disease in the United States, walked out smiling and unassisted from the Bethesda, Maryland, hospital where she was treated.

Emory University Hospital in Atlanta and the CDC also confirmed that the other nurse, Amber Vinson, no longer had detectable levels of virus but did not set a date for her to leave that facility.

Pham, who was transferred to the U.S. National Institutes of Health (NIH) Clinical Center in Bethesda, Maryland, from the Dallas hospital on Oct. 16, thanked her doctors at a news briefing.

Slideshow ( 16 images )

Looking fit in a dark blazer and a turquoise blouse, Pham said that even though she no longer is infected, “I know that it may be a while before I have my strength back.” She said she looked forward to seeing her family and her dog.

Photos of the Oval Office meeting showed Obama hugging Pham. Reporters and television cameras were not allowed in for the meeting.

Dr. Anthony Fauci, director of the NIH’s National Institute of Allergy and Infectious Diseases, said he could not pinpoint any one factor that contributed to Pham’s speedy recovery. He said it could be any of a number of factors, including the fact that “she’s young and very healthy” and was able to get intensive care very quickly.

Spencer finished his work in Guinea on Oct. 12 and arrived at John F. Kennedy International Airport in New York on Oct. 17. Six days later, he was quarantined at Bellevue Hospital with Ebola. The three previous cases diagnosed in the United States were in Dallas.

Three people who had close contact with Spencer were quarantined for observation. The doctor’s fiancée was among them and was isolated at the same hospital, and all three were still healthy, officials said.

The worst Ebola outbreak since the disease was identified in 1976 has killed at least 4,877 people and perhaps as many as 15,000, predominantly in Liberia, Sierra Leone and Guinea, according to the World Health Organization (WHO).

Spencer’s case brought to nine the total number of people treated for Ebola in U.S. hospitals since August. Just two, the nurses who treated Liberian national Thomas Eric Duncan, contracted the virus in the United States. Duncan died on Oct. 8 at Texas Health Presbyterian Hospital in Dallas, where Pham and Vinson were infected.

Obama’s response to Ebola ran into fresh criticism from Republicans during the congressional hearing.

Republican Representative Darrell Issa of California, who chairs the House of Representatives Oversight Committee, blasted the “bumbling” administration response, saying it had been characterized by missteps and ill-considered procedures to protect U.S. healthcare workers at home and troops in West Africa.

Local officials told New Yorkers they were safe even though Spencer had ridden subways, taken a cab and visited a bowling alley in Brooklyn between his return from Guinea and the onset of symptoms. Authorities on Friday declared the bowling alley safe.