NEW YORK – A nurse who treated Ebola patients in Sierra Leone is the first test case of quarantine policies now in effect in three states over heightened fears the deadly virus could be spread by health care workers returning to the United States.

The sketchy details of how such quarantines will be handled are drawing sharp criticism from humanitarian organization Doctors Without Borders, and infectious disease experts said Saturday that many of the logistics about enforcement are likely still up in the air.

Kaci Hickox, a Doctors Without Borders nurse, remained isolated at a hospital Saturday, a day after she returned to the U.S. and the governors of New York, New Jersey and Illinois announced mandatory 21-day quarantines for arriving travellers who had contact with Ebola patients in West Africa.

Health officials said Hickox was transported to a hospital after running a fever, but the nurse told the Dallas Morning News she was merely flushed because she was upset by a quarantine process she described as treating her like a criminal.

“This is not a situation I would wish on anyone, and I am scared for those who will follow me,” Hickox wrote in an essay for the newspaper.

Health officials said preliminary tests for Ebola came back negative for Hickox but Newark University Hospital would not say if she would be released for the balance of the quarantine period or remain in the hospital.

In the very early stages of Ebola, patients may still test negative because the virus has not yet reached detectable levels in the blood. The U.S. Centers for Disease Control and Prevention says it may take up to three days after the onset of symptoms for the virus to reach detectable levels in some patients, prompting repeat testing in some cases.

Doctors Without Borders executive director Sophie Delaunay complained Saturday about the “notable lack of clarity” from state officials about the quarantine policies, and an American Civil Liberties Union official in New Jersey said the state must provide more information on how it determined that mandatory quarantines were necessary.

“Coercive measures like mandatory quarantine of people exhibiting no symptoms of Ebola and when not medically necessary raise serious constitutional concerns about the state abusing its powers,” said Udi Ofer, executive director of the ACLU of New Jersey.

Doctors Without Borders said Hickox has not been issued an order of quarantine specifying how long she must be isolated and is being kept in an unheated tent. It urged the “fair and reasonable treatment” of health workers fighting the Ebola outbreak.

“We are attempting to clarify the details of the protocols with each state’s departments of health to gain a full understanding of their requirements and implications,” Delaunay said in a statement.

Indeed, health officials in all three states with quarantine policies did not return messages Saturday from The Associated Press seeking details about enforcement.

New Jersey Gov. Chris Christie, campaigning Saturday in Iowa for a fellow Republican, said he sympathizes for Hickox but said he has to do what he can to ensure public health safety.

“My heart goes out to her,” the governor said, while also noting that state and local health officials would make sure quarantine rules are enforced. He said the New Jersey State Police will not be involved.

Dr. Irwin Redlener, a Columbia University professor and director of the New York-based National Center for Disaster Preparedness, said the logistics of such a policy are “a problem.”

“The challenge now is how you translate this quarantine plan to operational protocol,” said Redlener, who attended a meeting with New York City Mayor Bill de Blasio and New York Gov. Andrew Cuomo on who should be under home quarantine and how to monitor them. That could involve case managers who keep an eye on home-bound people, Redlener said.

Cuomo and Christie on Friday imposed a mandatory quarantine of 21 days – the incubation period of the deadly virus – on travellers who have had contact with Ebola patients in the countries ravaged by the virus – Liberia, Guinea and Sierra Leone. A similar measure was announced in Illinois, where officials say such travellers could be quarantined at home.

The quarantine measures were announced after a New York physician, Craig Spencer, working for Doctors Without Borders returned from Guinea was admitted to Manhattan’s Bellevue Hospital Center earlier this week to be treated for Ebola.

His fiancee was released from Bellevue on Saturday night but will remain quarantined in the couple’s Harlem apartment. She and two of Spencer’s friends would remain quarantined until Nov. 14, officials said. They currently do not have any Ebola symptoms.

Hospital officials said in a statement Saturday that Spencer was awake and communicating and “experiencing gastrointestinal symptoms.”

De Blasio was not consulted by Cuomo about the new airport regulations, and the governor’s warning Friday that “hundreds and hundreds of people” could be infected by simply riding a bus with an Ebola patient ran contrary to the mayor’s attempts to tamp down public fear.

“We understand in a fast-moving situation, sometimes there will be moments where the communication is not everything we want it to be,” de Blasio said Saturday after he had lunch at a Manhattan meatball restaurant visited by Spencer earlier in the week.

A senior White House official said Saturday that how to treat health care workers returning from the affected West African countries continues to be discussed at policy meetings on Ebola as the administration continues to take a “careful look” at its policies.

At the same time, the administration, in considering policy changes, says it is trying to balance the public’s health and safety with the need to eliminate Ebola at the source.

“We will not hesitate to take any action that we feel has the potential to fortify us against additional imported Ebola cases,” the official said.

But Redlener warned that quarantines might discourage doctors and nurses from going to West Africa to help, an issue raised by aid groups and Dr. Rick Sacra, one of the American health care workers successfully treated for Ebola contracted while he worked in Liberia.

“Until Ebola is under control in Africa, we’re never going to see the end of such cases coming to the United States,” Redlener said.