BBC Canada on alert for mosquito virus

US scientists are working to control the virus

By Lee Carter in Toronto

Canadian health officials are trying to contain an outbreak of the potentially lethal West Nile virus which appears to have spread through most of the country's central urban regions.

The virus has been positively identified in four dead birds and several other bird carcasses currently being tested are also believed infected.

In rare cases the virus can be fatal and it has killed 10 people in the United States since first detected there three years ago.

One of the birds that tested positive was a bluejay, found just outside the country's most populous cities, Toronto.

And there are suspected cases in the nation's capital city, Ottawa.

Mosquito threat

The West Nile virus is spread by mosquitoes.

Most types of birds are vulnerable to West Nile, which can also be spread from bird to bird.

Mammals, including humans, are a lot less susceptible, and thousands of people may have been bitten by carrier mosquitoes and barely known it, or experience mild flu symptoms.

But in a small number of severe cases, the virus eventually makes its way into the brain, where it interferes with the functioning of the nervous system, leading to a coma and even death.

As mosquitoes are so plentiful, there is a limit to what authorities can do.

Government officials are trapping the insects to monitor the virus, and some jurisdictions are spraying insecticide.

'Avoid dusk'

Jill Bennet from the Essex county health unit, in south western Ontario, says they can only ask people to be vigilante by avoiding dusk, and eliminating likely breeding-grounds.

"We are asking individuals to look around their homes, and to see if there are any areas where there is stagnant water, eaves troughs or debris in eaves troughs, tyres in the backyards, screens in the homes that are in need of repair because of holes," says Ms Bennet.

The virus has been common in the Middle East since the 1930s, but the first North American case was only detected in 1990, in New York city.

The new Canadian findings means it has spread voraciously north and as far south as Florida.

-- Anonymous, August 26, 2001