NEW YORK (Reuters) - Illinois joined New York and New Jersey in imposing mandatory quarantines for people arriving with a risk of having contracted Ebola in West Africa, but the first person isolated under the new rules, a nurse back from Sierra Leone, strongly criticized her treatment.

Under a policy introduced on Friday, anyone arriving at John F. Kennedy International Airport or Newark Liberty International Airport after having contact with Ebola patients in Liberia, Sierra Leone or Guinea must submit to a mandatory quarantine for 21 days.

Three weeks is the longest documented period for an Ebola infection to emerge.

Ms Kaci Hickox, a nurse, returned on Friday from working with medical charity Doctors Without Borders in Sierra Leone and was placed in quarantine after arriving at Newark.

Ms Hickox, who was transferred from the airport to a hospital where she was placed in isolation, described a confusing and upsetting experience at the airport and was worried the same treatment was in store for other American health workers trying to help.

"I ... thought of many colleagues who will return home to America and face the same ordeal," Hickox wrote in an article published on Saturday by The Dallas Morning News with the help of one of the newspaper's reporters.

"Will they be made to feel like criminals and prisoners?" The state quarantines were imposed after a New York City doctor was diagnosed with the disease on Thursday, having returned this month from working with Ebola patients for Doctors Without Borders in Guinea.

Dr Craig Spencer, who is being treated in isolation at Bellevue Hospital Center in Manhattan, was the fourth person to be diagnosed with the illness in the United States and the first in the country's largest city.

His case set off renewed worries in the United States about the spread of the disease, which has killed thousands of people in West Africa.

Concern over Ebola in the United States has become a political issue ahead of Nov 4 congressional elections.

Illinois will also require a mandatory quarantine of anyone who has had direct contact with Ebola patients in those countries, Governor Pat Quinn said in a statement on Friday.

His announcement did not explicitly discuss it, but the new measure was likely aimed at people arriving at Chicago O'Hare International Airport.

The airport is one of five U.S. airports where health screening is in place for passengers whose journeys originated in the three West African countries that have borne the brunt of the worst Ebola outbreak on record.

Such passengers are now obliged to route their journeys into the United States through those five airports.

Mr Quinn's office and local health officials did not respond to requests for further comment.

Health officials in Virginia, where Washington Dulles International Airport is located, said the state is reviewing its quarantine policies.

In Georgia, where the Hartsfield-Jackson Atlanta International Airport is located, officials were not immediately available for comment.

The mandatory quarantines imposed by states exceed current federal guidelines, although the Obama administration is discussing similar measures.

President Barack Obama urged Americans on Saturday to be guided by "facts not fear" as they worry about the spread of Ebola. "We have been examining the protocols for protecting our brave healthcare workers, and, guided by the science, we'll continue to work with state and local officials to take the necessary steps to ensure the safety and health of the American people," he said in his weekly radio address.

New Jersey's health department said that Ms Hickox, the quarantined nurse, broke into a fever soon after being quarantined and was taken to University Hospital in Newark but later tested negative for Ebola.

In her article, Hickox disputed that account, saying her temperature was normal when tested orally at the hospital, but had shown a fever when she was tested using a non-contact forehead scanner, which reflected the fact she was flustered and anxious.

She said she was concerned other health workers would be treated in similar fashion. "I am scared that, like me, they will arrive and see a frenzy of disorganization, fear and, most frightening, quarantine," she said, published on the Dallas paper's website.

Doctors Without Borders also criticized Ms Hickox's treatment, saying she had been issued an order of quarantine but it was not clear how long she would be held in isolation, in uncomfortable conditions in a tent set up outside the main hospital building.

"Doctors Without Borders is very concerned about the conditions and uncertainty she is facing," the group said in a statement.

Ms Hickox's account echoed concerns of critics of the mandatory quarantines who say they could discourage Americans from going to help control the epidemic in West Africa.

Ebola has killed almost half of more than 10,000 people diagnosed with the disease - predominantly in Liberia, Sierra Leone and Guinea - although the true toll is far higher, according to the World Health Organization.

Representative Diana DeGette, a Colorado Democrat who was an early advocate of reassessing federal protocols on handling Ebola, warned against an over-reaction by health authorities.

"It's a very fine balance between getting our people to go over and help treat these Ebola patients - and they are very courageous to go on the front lines like that - and also make sure we protect public health," Ms DeGette said in an interview with CNN on Saturday morning.

The virus is not airborne but is spread through direct contact with bodily fluids from an infected person. It is not transmitted by people who are not showing symptoms, but the new quarantine measures were prompted in part by the fact that Dr Spencer traveled around the city between arriving home and developing symptoms on Thursday.