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North American cases of Ebola have raised concern about the disease spreading to Canada through land border crossings between Canada and the U.S.

The Windsor-Essex County Health Unit is worried Ebola could cross the border from Detroit.

Dr. Wajid Ahmed, the unit's public health adviser, says hospitals have protocol to follow if a person shows up with Ebola-like symptoms.

There is no strict screening process at North America's busiest land border crossing, the Ambassador Bridge, and the Detroit-Windsor Tunnel.

Ahmed says the fact border-crossers are in vehicles makes it even more difficult to identify sick people.

"I don't think that there is anything that we can do to protect ourselves, unless the person is really symptomatic and the border security forces identify them as an ill person and may contact us," Ahmed said.

Officials of the department of Homeland Security and the U.S. Centers for Disease Control said enhanced entry screening would occur at the following airports: New York's JFK International Airport, Washington-Dulles, Newark, N.J., Chicago-O'Hare and Hartsfield in Atlanta, Ga. Those airports are the destinations for 94 per cent of all U.S.-bound flights from the Ebola-affected countries.

According to the Detroit Free Press, 16 international flights arrive at Detroit Metro Airport each day.

The incubation period for Ebola is 2-21 days.

Wajid worries a person with Ebola could cross into Windsor before the symptoms are visible.

Last week, federal Health Minister Rona Ambrose announced that quarantine officers will be stationed at six airports across Canada. They are: Montreal, Toronto, Vancouver, Halifax, Ottawa and Calgary.

She never mentioned land crossings.

However, in an emailed response to a request for information, the Public Health Agency said border agency officers at crossings that do not have a quarantine officer present can connect via technology with one around the clock.

Border crossing concerns U.S. politicians

The growing sense of concern about the North American spread of Ebola was reflected in a congressional hearing Thursday in Washington. One lawmaker even briefly questioned whether the Canadian border might need to be better secured.

The reference to the 49th parallel came from a Tennessee Republican, who during a House hearing asked whether America's land borders were safe from the deadly virus.

"Do we need to worry about having an unsecure southern and northern border?" Marsha Blackburn, the vice-chair of the House energy committee, asked. "Is that a big part of this problem?"

No, said the witness in question, Dr. Tom Frieden, the head of the Centers for Disease Control, who spent three hours Thursday taking questions from politicians.

Blackburn, it turns out, misunderstood Frieden's reference to "overland travel" -- he was talking about West Africa, not North America. But the exchange illustrates the growing anxiety in the U.S., and the extent to which the virus is becoming a political football with congressional elections barely two weeks away.

The fear is being fuelled by the death of a tourist from Africa, the spread of the disease to two medical workers who treated him and, finally, an admission from the health-care system that it goofed in the initial response.

The Canada Border Services Agency was not immediately available for comment.

Jean-Pierre Fortin, the national president of the Customs and Immigration Union, which represents CBSA agents, says he is not aware of any specific measures in place at land border crossings.

Speaking in French to Radio-Canada, Fortin said no measures have been brought to the union’s attention by the Canadian Border Services.

Fortin said land border agents are paying "some" attention to people crossing into Canada who may potentially be infected with Ebola.