A woman lying quarantined in a Canadian hospital after arriving from central Africa has been found free of the deadly Ebola virus, raising new fears on Wednesday that a more mysterious disease could have been brought to North America's shores.
The woman, who flew to Toronto from the Democratic Republic of Congo via New York on Saturday, was admitted to a hospital in Hamilton, Ontario, on Sunday.
Canadian health officials on Wednesday ruled out Ebola - the incurable disease that recently killed hundreds in Uganda - could still have a lesser known type of tropical viral hemorrhagic fever.
"Ebola has been ruled out from Health Canada's perspective," said Dr. Douglas MacPherson, an infectious disease specialist at the federal health department.
"There are still other viral hemorrhagic tropical fevers under consideration," he added.
The case, which is gaining wide media attention, had raised fears the woman had brought the first case of Ebola to North America.
But infection control specialists said on Wednesday that the best case scenario would be an Ebola diagnosis, because doctors would then know what they were dealing with and how to contain it.
"The worst case scenario is definitely not Ebola. Everyone wanders around saying Ebola is incredibly dangerous and it is not," Dr. Allison McGeer, director of infection control at Mt. Sinai Hospital in Toronto, told Reuters.
"I know my infectious disease colleagues are saying 'we aren't worried if this is Ebola, it's if it is not Ebola that there is something to worry about'," said McGeer.
Ebola and other viral hemorrhagic fevers are spread through human excretions such as blood, semen, saliva and mucous, and are not as contagious as airborne diseases like tuberculosis.
"She could have some brand new hemorrhagic fever that nobody has yet described...the biggest concern that most of us have is this is some other virus that is transmitted by an airborne route, which is incredibly unlikely," said McGeer.
McGeer doubts a diagnosis will ever be made, and questioned why the woman would have Ebola after coming from a country without a recent history of Ebola infection.
Ebola, which is not curable, first emerged in the Democratic Republic of Congo, formerly known as Zaire, in 1976. The last major Ebola occurrence, in Uganda last September, killed 173 people, and officials recently said the outbreak has most likely run its course.
Most victims die from shock after days of high fever, vomiting and extensive bleeding.
While the condition of the woman in hospital remains serious, signs of late stage Ebola infection, such as bleeding ears and eyes, have not been part of her symptoms, and she is showing some clinical improvement, said Mark Loeb, an infectious disease expert at Hamilton Health Sciences Corp.
Test results from a special laboratory in Winnipeg, Manitoba, are expected by Wednesday evening at the earliest, and will be released to the public after being analyzed by attending doctors, said MacPherson.
Health officials said they are still being "super cautious" when treating the woman and continue to monitor people who came in close contact with her, including two of her personal contacts and ten hospital workers.