10/09/2014 05:37 EDT | Updated 12/09/2014 05:59 EST

Ebola entry screening at airports unlikely to catch many cases, expert warns

TORONTO - A Toronto researcher who studies the global spread of infectious diseases says Canada's plan to beef up entry screening of passengers coming from West Africa may make people feel safer, but is unlikely to produce much in the way of results.

Dr. Kamran Khan says he understands the impulse to want to do something to prevent importation of Ebola into this country.

But he says, in reality, entry screening efforts may be a waste of resources that would be better spent on containing the outbreak in West Africa.

Khan is a researcher at the University of Toronto; his specialty is using global airline data to figure out the risk that a disease such as Ebola or Middle East respiratory syndrome will travel from one place to another.

Canada announced Wednesday that it would heighten its efforts to stop Ebola from entering the country by doing temperature screenings on some travellers from West Africa.

People from that region who acknowledge feeling unwell or admit to having had contact with a sick person will be assessed and may have their temperature taken.

Khan says that relies on people admitting to something few might be willing to do in the current climate.

"You could imagine going through a screening and declaring, 'I think I might have Ebola.' I think every traveller knows what might follow with that," he said in an interview from Shanghai, China.

"I don't want to be cynical. And there are probably some very honest souls out there. But we've seen people actually actively travel while they've known they've had contacts and potential (Ebola) exposures and so on."

Entry and exit screening was used during the 2003 SARS outbreak, with Canada and other countries installing thermal scanning devices in international airports. Studies after the fact found the programs to be largely ineffective.

The same was true during the H1N1 flu pandemic in 2009. A study Khan and colleagues did looking at the spread of that disease found that entry screening really didn't work. Exit screening from a source country early in an outbreak might have more impact, that study said.

The countries in the grip of the Ebola outbreak are screening travellers leaving the country — though the recent case of a man who left Liberia and travelled to Dallas, Texas, before developing the symptoms of Ebola show the weakness of the system.

The man, Thomas Duncan, died Wednesday.

When he left Liberia, he filled out a form saying he was not ill and had had no known contact with a person infected with Ebola. Later it emerged he had helped a neighbour's daughter who was trying to get admitted to a hospital because she was ill and pregnant. She later died.

Duncan was not visibly sick when he arrived in the United States. It was only four days after he arrived that the symptoms of Ebola started.

The disease has a very long incubation period. It may take up to 21 days for people who are infected to develop symptoms, though the average time is between eight and 10 days.

That is plenty of time to move around the world, Khan notes.

Canada has no direct flights with the affected West African countries and few people from there come here. Only about 1.5 per cent of all air travellers leaving the three most affected countries every year come to Canada, Khan's research shows.

Given all those factors, he thinks Canada would be better off spending the money it will invest in this program on helping contain the outbreak in Africa.

"I understand because there is public fear and concern. But to me it feels a little bit like the energy is being put into a place that's not as effective as being much more active in the source countries themselves," he says.

"I'm just thinking in terms of bang for the buck. I think there's greater bang for the buck in responding upstream in the countries relative to downstream in a country like Canada."