By Rich McKay

ATLANTA (Reuters) - An American missionary stricken with Ebola in West Africa wore a protective white suit on Tuesday as she was wheeled on a stretcher into the Atlanta hospital where doctors will try to save her and a fellow aid worker from the deadly virus.

Nancy Writebol, 59, arrived in the United States after being flown overnight from Liberia and will be treated by infectious disease specialists at Emory University Hospital, according to Christian missionary group SIM USA.

She will be in the same isolation ward as Kent Brantly, 33, an Ebola-infected American doctor who was able to walk into the hospital when he arrived by ambulance on Saturday.

The pair, who served on a joint team in Monrovia run by Christian aid groups SIM USA and Samaritan's Purse, are believed to be the first Ebola patients treated in the United States.

"We are tremendously relieved that our mother is back in the U.S.," Jeremy Writebol, one of the missionary's two sons, said in a statement.

Health officials have said the virus does not pose a significant threat to the American public.

There is no proven cure for the contagious hemorrhagic disease, which has killed nearly 900 people in Africa since February in the worst Ebola outbreak on record. The death rate in the current epidemic is about 60 percent, experts say.

The relief groups have said the condition of each aid worker improved in Liberia after the pair received an experimental drug developed by a San Diego-based private biotech firm and previously tested only in monkeys.

Bruce Johnson, president of SIM USA, said he did not know if Writebol and Brantly would get more of the drug at Emory, and representatives for Samaritan's Purse and the hospital declined to comment on specific treatments.

Brantly's wife said she had seen him every day in Atlanta and that he continued to improve.

"I know that Kent is receiving the very best medical treatment available," Amber Brantly said in a statement.

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TESTS IN OHIO, NEW YORK

Writebol and Brantly returned to the United States separately because the plane equipped to transport them could carry only one patient at a time. Johnson said doctors in Liberia made the decision to send Brantly home first.

The plane carrying Writebol landed Tuesday at Dobbins Air Reserve Base in Georgia, where she was transferred to an ambulance and taken to the hospital. The two paramedics who transported Writebol into the hospital also wore white, full-body biohazard suits to avoid any direct contact with her.

Johnson said it was still unknown how Writebol contracted Ebola. A longtime missionary from Charlotte, North Carolina, Writebol had been working for SIM USA as a hygienist who decontaminated protective suits worn by healthcare workers inside an isolation unit at a Monrovia treatment center.

The low survival rate for Ebola patients had her sons and husband, David, a fellow missionary in Liberia, thinking about funeral plans just a week ago, Johnson said.

"Now we have a real reason to be hopeful," Johnson said David Writebol told him.

Plans are being made to fly David Writebol to Atlanta to be with his wife, Johnson said.

Costs for the care and transportation of Writebol and Brantly have topped $2 million, with about $1 million spent by SIM USA and more than $1 million by Samaritan's Purse, Johnson said.

Writebol's arrival came as health officials in New York and Ohio said they had run tests for Ebola on two people who had traveled recently to West Africa.

A man who arrived on Monday at Mount Sinai Hospital in New York City with a high fever and stomach ache was stable and unlikely to have Ebola, the hospital said. He remained in isolation on Tuesday.

A 46-year-old Columbus, Ohio, woman also was tested for Ebola after showing signs of illness but the results came back negative for the virus, Columbus public health officials said.

(Reporting by Rich McKay; Additional reporting by Barbara Goldberg and Sharon Begley in New York and Kim Palmer in Cleveland, Ohio; Writing by Colleen Jenkins; Editing by Scott Malone, Doina Chiacu and Eric Beech)