MONTREAL -The early discovery of an infected bird has prompted Canadian health officials to speed up their attack against the West Nile virus.

In Newmarket, Ont., where the first infected bird was found a month earlier than last year, health officials plan to move up the timetable for spreading larvicide to help prevent mosquitoes from growing out of the larval stage. Methoprene will be dispersed in catch basins starting in May, a few weeks earlier than originally planned.

"We actually planned on starting late in May and we're going to bump that up now as a result of finding a bird already," said Patrick Casey, spokesman for York Region, a bedroom community of Toronto.

A Health Canada official cautioned that the infected bird may only have been found earlier than before because Ontario moved up the start of its monitoring system.

Last year, York Region reported six confirmed and four probable cases of West Nile. In Ontario, there were 17 deaths.

In Quebec, authorities began spreading the biological larvicide BTI in one Montreal borough on Monday as scheduled. The substance will be sprayed on stagnant water in the west end of the island for up to three weeks.

Other Montreal-area communities will follow suit.

"It's certain that we won't kill all mosquitoes but with this preventive measure, we hope to reduce the transmission of the virus to a minimum," said Blaise Lefebvre, spokesman for the Montreal public health department.

The use of the biological larvicide is safe for humans and animals, he said.

Across Canada, governments at all levels have been working over the winter to finalize strategies to combat the deadly virus.

"We know that the virus is alive in the province of Quebec," said Dominique Breton, a spokeswoman for the province's Health Department. "We are ready."

The province plans to spend $11 million as part of its first formal action plan to fight the virus. The plan includes footing the entire cost of spreading larvicides, increasing to 75 the number of monitoring stations that will detect the virus and starting a toll-free number May 5 for people to report dead birds.

The first cases of West Nile were detected in Quebec residents last year. Two of the 16 Quebecers diagnosed with the virus died.

Manitoba will start its monitoring program on May 1. The virus was detected in birds last year in Nova Scotia, Quebec, Ontario, Manitoba and Saskatchewan. Only Newfoundland is expexcted not to have any formal monitoring system this year.

Ontario will distribute brochures to homes and launch television and radio advertising campaigns.

The key message is that people cover up, use bug spray and eliminate standing water around their homes.

Health Canada said the early finding of an infected bird suggests the virus may be able to survive the Canadian winter, even a particularly cold one.

"It would be a bigger risk if the virus can overwinter," said Dr. Harvey Artsob, chief of Health Canada's viral zoonotics and special pathogens divisions.

"In theory there could be infected mosquitoes in many different regions in Canada if it just doesn't have to be reintroduced and survives over the winter."

Much about the virus remains unknown but recent research indicated the disease is passed on from female mosquitoes to their eggs. It could also be hosted in mammals.

"Canadians need to have a personal protection plan in place before mosquitoes start to feed and breed in earnest," said Barry Tyler, an Ontario entomologist.

The early finding of an infected bird is a worrying omen that the virus will spread further north this year.

"Each year it spreads so we believe this year it will appear earlier and spread north."

But Artsob hopes larvicide programs and other interventions will ultimately reduce the number of human cases this year.

The first sign that West Nile had moved into Canada came two years ago when a dead bird found in southern Ontario was confirmed to have died of the virus, which is transmitted to humans by bites from infected mosquitoes.

The first human cases were confirmed last summer.

Like SARS, West Nile has a wide spectrum of symptoms - a mild flu-like condition, aches, fatigue and runny nose.