A person who recently travelled in West Africa is being assessed in a Toronto hospital to see if she has Ebola.

But an infectious diseases expert at Sunnybrook Health Sciences Centre says the likelihood the person will test positive for the infection appears to be low.

Dr. Andrew Simor said the unidentified woman had been in Guinea. But the hospital believes she left that country more than 21 days ago. The incubation period for Ebola — the time from infection to when symptoms become apparent — is between two to 21 days.

"At this point we think it’s highly unlikely based on the history that we have available to us. But we are being cautious because we want to be sure that we got the history right," said Simor, the hospital’s chief of microbiology.

"The only reason that we’re taking the precautions is because of a language barrier. English is not her first language. The story in terms of the timing of her travel is not 100 per cent clear. And so that’s the reason we’re being cautious."

The woman arrived for care on Wednesday morning. She is experiencing fever and nausea, which are early symptoms of Ebola. But they are also symptoms of many other ailments.

Simor said the woman is not acutely ill. She is being treated in an isolation room by a small team of staff trained in delivering care while garbed in the protective gear needed to handle Ebola patients.

He said initial results of her blood test may be available Wednesday evening.

Canada has never had an Ebola case diagnosed within its borders.

But during the ongoing West African outbreak, a number of people suspected of having the disease have been tested — and ruled out — in various parts of the country.

The World Health Organization said Wednesday that since the outbreak started in late 2013, there have been 24,701 cases, mainly in Guinea, Sierra Leone and Liberia. Of those, 10,194 people have died.