TORONTO — Everyone knew it was coming. But no one suspected West Nile virus would hit with such a wallop when it arrived. The virus, spread by mosquitoes and endemic to Africa, West Asia and the Middle East, had never infected a Canadian in Canada before this year, as far as medical experts could tell.

That changed, big time, in 2002. There were over 200 confirmed and probable cases of West Nile in Ontario and Quebec. At least nine people who had the virus died, although West Nile has not been fixed as the cause of death in all those cases.

Given the West Nile rule of thumb - between 150 to 300 mild, undetected infections for every person who gets very sick with the virus - the number of human cases in Canada this year was likely in the tens of thousands.

"It's staggering. To be honest with you, if someone had told me last year at this time next year that you're going to have had so many cases in Canada, wow, I would have been shocked," says Dr. Harvey Artsob, chief of zoonotic diseases at Health Canada's National Microbiology Laboratory in Winnipeg.

So far the human cases have been restricted to Central Canada, but the virus was also found in dead birds in Manitoba, Nova Scotia and Saskatchewan.

To date, Ontario has had 77 confirmed cases and 148 "probables" awaiting confirmatory testing. Quebec had seven confirmed cases, and two probables. As well, as many as 300 other people showed antibodies to West Nile virus in a blood test, but a second test, needed to confirm the diagnosis, hasn't been and may never be completed.

Two people from Alberta got the virus, but both were infected on travels outside the province.

The virus's wildfire spread through the United States, where the virus is now known to be present in most of the lower 48 states, suggests residents of most other provinces can expect a new and unwelcome pathogen on their doorsteps perhaps as early as next summer.

"Scientifically one can't talk about certainties. But I think it's very possible that we'll see West Nile in at least nine of our Canadian provinces, based on the pattern of spread we've seen," Artsob predicts.

Newfoundland's geographic isolation may protect it from West Nile, he suggests. As well, it's unclear the virus could ever get a good foothold in the three territories, because the species of mosquitoes which spread it don't do well in the North's climatic extremes.

John Stevens from Burlington, Ont., has the dubious distinction of being the first Canadian confirmed to have been infected with West Nile within Canada.

Stevens was lucky. He didn't develop the encephalitis (brain swelling) which accompanies the most serious West Nile cases and which causes lasting after-effects in some cases. Still, the fit 51-year-old trucker was shocked at the toll the virus took on him.

"I mistook how long it takes to get better," he admits. "Probably at least a good month minimum. Might even be six weeks."

In fact, that's another feature of Canada's 2002 West Nile experience that has surprised experts.

Many of the people who became seriously ill with West Nile suffered a sort of temporary paralysis resembling polio, which was something that hadn't been seen before. And many West Nile sufferers took considerably longer to recuperate than had been expected, based on the disease's pattern in parts of the world where it is well established.

When it became evident in 2001 that West Nile virus had moved into Canada, experts had gone out of their way to assuage public fears.

They urged people to take precautions - use DEET-based bug sprays, wear light-coloured and long-sleeved clothing while outdoors - but stressed that the disease was unlikely to rival influenza as a health risk. (About 1,500 people in Canada die from influenza every year.)

Now, some are admitting the virus was more of a heavyweight than they had anticipated.

"Yeah. I think that's fair," says Dr. Donald Low, chief microbiologist at Toronto's Mount Sinai Hospital.

"There's no question that in the magnitude of things, it's a small player when you look at well-established pathogens like influenza and pneumococcal pneumonia. But I think we didn't expect this kind of impact. And also, we didn't expect this kind of neurological disease.

"The flaccid paralysis, the requirement for ventilatory support, muscle weakness: I mean these are things that really aren't well described in the previous outbreaks.

"It appears as if the virus is either changing its characteristics or becoming more virulent."

Other surprises from 2002: The virus can be transmitted via breast milk, organ transplant and blood transfusions.

That last point became evident when an American woman succumbed to West Nile after contracting it from a unit of blood. An Ontario woman who had the disease and died is strongly suspected to have acquired it through a transfusion.

That's causing serious headaches at Canadian Blood Services, the agency set up to run the country's blood donation system after the public and policy makers lost confidence in the Canadian Red Cross over the scandal involving blood tainted with hepatitis C.

Canadian Blood Services recently announced a recall of frozen blood products drawn from Ontario donors last summer because of the risk of West Nile transmission.

There is currently no test to screen prospective blood donors for the virus, although work is underway in the United States to devise one. The blood agency hopes the test is available by the time West Nile season rolls around next summer, but is working on contingency plans in case it is not, says Dr. Heather Hume, executive medical director.

"It certainly creates some challenges, indeed," Hume admits. "We are somewhat limited in what we can do if there is no test."

One option: Ramp up production of plasma - the frozen blood product that can be stored for up to a year - in the winter months. Other blood products - platelets and red blood cells - can't be stockpiled in the off-season as they have much shorter shelf-lives.

"We would do what we could in the absence of a test," Hume says, but noting the service won't be able to eliminate risk of infection by transfusion until there is a test.

"Do we say we don't collect in areas of the country where there are lots of mosquitoes? There are not very many areas in Canada that don't," she says.

"Trying to collect only in certain areas would almost certainly lead to a larger issue of lack of supply and potential death because there wasn't enough blood."

While the blood service wrestles with those issues, provincial and municipal public health officials in many areas are going to have to grapple with another: To spray or not to spray?

Widescale applications of mosquito-killing chemicals may help with the West Nile problem but may cause others, experts admit.

"That's going to be a tough decision because a lot of people are not going to be happy with that," says Low.

Another option: applying larvicides in mosquito breeding grounds. It's a more environmentally acceptable option, but issues of where, how much and at what cost remain to be worked out.

In the meantime, John Stevens is putting in place contingency plans of his own.

His bout with West Nile has left him immune to the virus. But his wife, who has heart problems, is not. And Stevens knows that in her weakened state, a case of West Nile could be life-threatening.

So the Stevens have made some lifestyle changes. They have a pool and used to love to swim and sit around the pool on warm evenings. That's a thing of the past.

"We just stopped going outdoors in the evening," he explained. "It's as simple as that. Basically once the sun goes down we don't go outside anymore."

Some facts about West Nile virus:

First found in North America: The disease first struck in New York City in the summer of 1999, killing seven people, including one Canadian who became ill while visiting the city.

First found in Canada: Infected dead birds were first found in Ontario in the summer of 2001. No human cases were confirmed that summer.

Virus spreads: In 2002, signs of the virus were found in Ontario, Quebec, Manitoba, Saskatchewan, and Nova Scotia. The virus begins infecting humans.

Human cases: Human cases were reported in Ontario and Quebec. The single case in Alberta appears to have been contracted in the United States.

Numbers: Figures aren't conclusive, because as many as 100 cases remain to be confirmed. But so far Quebec reports seven cases confirmed and two probables. Ontario reports 77 confirmed cases and 148 probables.

West Nile deaths: Getting a precise handle on this is difficult. Some people known to have been infected with West Nile actually died of other causes. It is known that eight people who died in Ontario had the virus and another case remains to be confirmed. One person died of the disease in Quebec.

Other species hit: The virus causes illness and death in a wide range of species including horses, birds, apes, squirrels, dogs, wolves, reindeer, mountain goats.