OTTAWA -- Health officials in Canada are expanding their monitoring of ticks for an extremely rare but potentially deadly virus after a dramatic rise in the number of cases of the disease south of the border.

The Public Health Agency of Canada says it's broadening screening for Powassan virus in the tiny, blood-sucking arachnids to include blacklegged ticks.

Human cases of the virus, which can cause encephalitis, or inflammation of the brain, have been reported this spring in New York, New Jersey, Massachusetts and Maine, prompting several other states to be on the lookout for the disease.

The virus was first identified in 1958 in Powassan, Ont., where a child who contracted the disease later died.

Since then, only 16 human cases have been reported in Canada.

But health officials say the numbers of blacklegged ticks have expanded rapidly in Canada over the last 10 years.

Powassan virus has been detected in groundhog ticks and blacklegged ticks from New Brunswick, Nova Scotia, Prince Edward Island, Quebec, Ontario, Alberta and British Columbia.