A nurse who returned to the US after treating Ebola patients in Sierra Leone has defied a quarantine for health care workers, leaving her home in Fort Kent, Maine, to go for an hour-long bike ride.

Kaci Hickox defied the quarantine on Thursday despite state officials saying on Wednesday that they would seek a court order to enforce the quarantine if she left her house before November 10.

"I'm free to go on a bike ride in my home town," the 33-year-old nurse told reporters as she arrived back at her home.

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Hickox, who tested negative for the virus on her return, said she plans to take the issue to court if Maine does not lift the quarantine.

The 33-year-old previously blasted New Jersey Governor Chris Christie after she was taken from an airport and put in quarantine in a tent before being driven to her home in Maine to spend the rest of the 21-day quarantine.

Twenty-one days is the maximum incubation period for Ebola.

Hickox contends there is no need for quarantine and has called the measure "scientifically unsound".

Ebola is spread through contact with bodily fluids from a person showing symptoms and is not airborne.

More than 13,700 people have contracted Ebola, with nearly 5,000 killed by the virus, all but a few of them in Sierra Leone, Guinea and Liberia.

Source: Agencies