"If the restrictions placed on me by the state of Maine are not lifted by Thursday morning, I will go to court to fight for my freedom," she said in an interview on NBC's "Today" program.

In several media interviews, Ms Hickox said she was in good health and had not had any symptoms of the virus that signal a period when an infected person would be contagious. Speaking from her home in Fort Kent, Maine, she said she had been monitoring her condition and taking her temperature twice a day.

But she sharply criticized state guidelines that would require her to stay isolated at home for 21 days, saying she was "appalled" at restrictions she deemed unconstitutional and not based on science.

"I don't plan on sticking to the guidelines," she told NBC.

Lawyers for Ms Hickox told ABC and NBC that Maine officials would have to go to court to get an order to enforce a quarantine and that, if the state does, their client would challenge it.

Ms Hickox worked with the medical organization Doctors Without Borders to help treat patients with the virus in Sierra Leone and fought earlier isolation in New Jersey.

"I feel absolutely great," she told ABC's "Good Morning America" program. "I am completely symptom-free."