A Congolese woman suffering from a mysterious tropical disease was placed on life support in a Canadian hospital on Thursday as international experts stepped up their hunt to find the virus threatening her life.

Health officials have already ruled out the chance that the woman who has not been named, is suffering from the deadly Ebola virus, which killed over 170 people in a recent outbreak in Uganda and which is almost always fatal.

She has been in strict quarantine in a Canadian hospital since she was taken seriously ill at the weekend, soon after arriving in Canada from the Democratic Republic of Congo.

"The bad news is the patient took a turn for the worse last night and is now in critical condition on life support," said Dr. Mark Loeb, an infectious disease specialist at Hamilton Health Sciences Corp.

Doctors said her worsening symptoms include liver failure.

Canadian health officials said on Wednesday that tests showed the woman was not suffering from Ebola, and they now suspect one of a handful of other tropical viral hemorrhagic fevers.

"The Ebola testing to date is negative according to our lab in Winnipeg, but a number of other possible hemorrhagic fevers have not been ruled out," said Dr. Douglas MacPherson, an infectious disease specialist at Health Canada.

The case, which has garnered significant media attention, had raised fears that the woman had imported the first case of Ebola to North America.

Ebola and other hemorrhagic fevers are spread through human secretions such as blood, semen, saliva and mucous. Victims die from shock after days of fever, vomiting and heavy bleeding.

"We are pressing very hard to get the diagnostic testing from the Winnipeg lab, and the international agencies that have this as their top priority," added MacPherson.

The Center for Disease Control and Prevention in Atlanta said it had received samples from Canada early on Thursday, but was not sure how long it will take to run the requisite tests.

"They (Health Canada) haven't even ruled out certain things so we don't know how long these tests will take," a CDC spokesman told Reuters.

Ebola and other hemorrhagic fevers are only spread through close contact with an infected person, but Canadian officials say they are being very cautious with the patient.

A total of 63 healthcare and laboratory workers who may not have been wearing adequate protective gear when handling the woman or her samples are being monitored closely, although Loeb said none were showing worrisome symptoms.

Health officials have repeatedly assured the public that there is virtually no chance anybody was infected on the woman's journey to Canada via New York because her symptoms did not materialize until she arrived in Canada.

"We remain confident that her period of illness began only in Hamilton," said MacPherson in reference to the city of 350,000, situated 60 km (40 miles) to the west of Toronto.

Ebola first emerged in the Democratic Republic of Congo, formerly known as Zaire, in 1976.

Some Canadian infection control specialists say it is unlikely that a definitive diagnosis will ever be made and the best case might actually have been a diagnosis of Ebola.

"If it's Ebola we know what we are dealing with and we don't have to worry. There is a 65 to 75 percent chance we will never know," said Dr. Allison McGeer, direction of infection control at Mt. Sinai Hospital in Toronto.

(From ChinaDaily)