A possible case of Ebola has been detected in Canada after a passenger returned from Africa where dozens have died from the virus.

"All we know at this point is that we have a person who is critically ill who travelled from a country where these diseases occur," said Denise Werker, joint director of health in Saskatchewan province in western Canada.

She said the casualty had been in Liberia and had developed the symptoms after landing in Canada. He or she would not have been contagious when travelling and was now in isolation pending test results.

Aid workers and health officials in Guinea are battling to contain western Africa's first outbreak of the deadly Ebola virus as neighbouring Liberia reported its first suspected victims.

At least 59 people are known to have died in Guinea's southern forests, but the Liberian cases - if confirmed - would mark the first spread of the highly contagious pathogen into another country.

Ms. Werker said the risk of transmission was low as the disease, one of the world's most virulent, is transmitted to humans from wild animals.

It is transmitted between humans by direct contact with blood, faeces or sweat, or by sexual contact and the unprotected handling of contaminated corpses.