(Reuters) - A nurse who treated Ebola patients in Sierra Leone but has tested negative for the virus ventured out of her home in Maine and took a bike ride on Thursday, defying a quarantine order and setting up a legal collision with state authorities.

Attorneys for Kaci Hickox, 33, said they had not yet been served with a court order to enforce a 21-day quarantine - matching the virus's maximum incubation period - but remained prepared to fight such an order if necessary.

Hickox left her home in the small Maine town of Fort Kent, along the Canadian border, and television news images showed her taking a morning bicycle ride with her boyfriend. Hickox has given the state a deadline of Thursday to lift an order that she remain at home until Nov. 10, or she will go to court.

“It’s a beautiful day for a bike ride,” said Hickox, dressed in bike gear including a helmet as she headed out for a three-mile (5 km) ride while police stationed outside her house stood by without trying to stop her, according to local media.

Maine Governor Paul LePage, a Republican locked in a tough re-election battle, said he is seeking legal authority to keep Hickox isolated at home.

President Barack Obama, who has criticized state mandatory quarantine policies for returning medical workers like Hickox, was scheduled to arrive in Maine later on Thursday to campaign for Democratic candidates including Mike Michaud, who is trying to unseat LePage in Tuesday's mid-term elections.

Norman Siegel, one of Hickox's lawyers, defended her decision to go for a bike ride as a public statement but noted that she avoided the center of town so as not to “freak people out.”

“Since there’s no court order, she can be out in public,” Siegel said. “Even if people disagree with her position, I would hope they respect the fact that she’s taking into account the fear, which is based on misinformation about the way the disease is transmitted.”

Medical professionals say Ebola is difficult to catch and is spread through direct contact with bodily fluids from an infected person and is not transmitted by asymptomatic people. Ebola is not airborne.

Siegel also criticized LePage for stoking fear of Ebola rather than using his office to educate the public about the disease.

"People tell me politics isn’t involved in this?” Siegel said. “Give me a break.”

Concern about Ebola is high in the United States even though there is only one person in the country currently being treated for it, a New York doctor who cared for patients in West Africa. But with elections next Tuesday, Republicans aiming to take full control of the U.S. Congress have made criticism of Obama's response to Ebola - they call it inept and too weak - a part of their campaign message.

The nurse's confrontation with Maine officials highlights how states have been struggling to protect their citizens from Ebola without resorting to overzealous, useless precautions or violating civil rights.

Hickox says she is completely healthy and has been monitoring her condition and taking her temperature twice a day.

Hickox tested negative for Ebola after returning from working with the humanitarian group Doctors Without Borders in Sierra Leone, one of the three impoverished countries at the heart of an outbreak that has killed about 5,000 people, all but a handful in West Africa. The disease causes fever, bleeding, vomiting and diarrhea.

Hickox previously blasted New Jersey Governor Chris Christie after she was taken from Newark's airport and put in quarantine in a tent before being driven to Maine to spend the rest of her 21-day quarantine at home.

Her town is in Maine's sparsely populated far north, more than 300 miles (480 km) from the state's largest city, Portland, and further north than Quebec City in neighboring Canada.


Under Maine law, the state health department can seek an emergency court order placing an individual in its custody if it shows a judge “clear and convincing evidence” that the person must be held “to avoid a clear and immediate public health threat.”

If a judge grants the order, the patient is entitled to a hearing within 72 hours, not including weekends, to challenge the ruling.

Some U.S. states have imposed automatic 21-day quarantines on doctors and nurses returning from treating Ebola patients in Liberia, Sierra Leone and Guinea. Obama and other critics say such steps may discourage American doctors and nurses desperately needed in West Africa from volunteering.

New York Governor Andrew Cuomo and New York City Mayor Bill de Blasio announced a program of financial incentives and other employment protections to encourage healthcare professionals to travel to West Africa to fight Ebola.

Cuomo is among the governors who has imposed 21-day quarantines for doctors and nurses returning from the three countries.

U.S. Representative Steve Cohen, a Tennessee Democrat, said the fight over Hickox and the larger battle over isolation policies have deteriorated into political posturing just days ahead of the elections.

“This is strictly driven by politics and fear-mongering,” Cohen told CNN.

(Additional reporting by Brendan O'Brien, Susan Heavey and Roberta Rampton; Writing by Will Dunham; Editing by Jonathan Oatis and Grant McCool)