Public health officials in Ontario and Manitoba say it's a matter of time before someone in Canada is infected with the West Nile virus – if it hasn't happened already.

Some may have already been infected and recovered without ever knowing they had it, they say.

"It is possible that people have been exposed, because we know there have been mosquitoes and birds in our area that have tested positive," said Dr. Karl Kabasele, staff physician on the Toronto Board of Health West Nile virus campaign.

The virus is usually found in birds and can be transmitted to humans through mosquito bites.

An outbreak in Louisiana has grown to 71 confirmed cases of Tuesday. Five people there have died.

But officials in Ontario say there is no need to panic.

Ontario's Chief Medical Officer, Dr. Colin D'Cunha, said the growing alarm is being driven by hype rather than by facts. "The problem is when you've got a disease that is 'new' and in the environment, and people die – instant headline!" he said.

D'Cunha says West Nile is only dangerous to a small number of people, those who are old or who are already sick. He says the common flu poses more of a risk.

Health officials say that when the virus does infect people in Canada – as they say it inevitably will do – most healthy people will be able to fight it off.