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Controlling the Ebola virus outbreak at the source in West Africa is the most effective way to decrease international risk of transmission, a new study published in The Lancet has found.

If the epidemic persists and grows, it’s likely there will be more cases of the deadly virus exported to other countries, including Canada, via air travel, said Dr. Kamran Khan, an associate professor at the University of Toronto's department of medicine, division of infectious diseases, department of health policy, management and evaluation, and a researcher at .

His work is making headlines around the world. (Read articles in the and the .)

Khan, who examines global airline travel patterns to predict the spread of diseases, said that every month, three Ebola-infected travellers are likely to leave West Africa, which is experiencing a widespread outbreak of the virus – and this number would only increase as the epidemic grows.

Khan and his co-authors said it is essential that other countries, their public health agencies and hospitals be prepared. The risk of international spread would be further compounded if this epidemic were to take hold in other countries, especially those with weak public health systems.

“The international community must be mindful and be ready to support the early detection and control of cases should they be imported into resource-limited countries,” Khan said.

Khan noted that of the almost 500,000 travellers who flew on commercial flights out of Guinea, Liberia or Sierra Leone in 2013, more than half were headed to destinations in five countries: Ghana (17.5 per cent), Senegal (14.4 per cent), the United Kingdom (8.7 per cent), France (7.1 per cent) and Gambia (6.8 per cent). More than 60 per cent of travellers from those countries in 2014 are expected to have final destinations in low- or lower-middle income countries.

“Given that these countries have limited medical and public health resources, they may have difficulty quickly identifying and effectively responding to imported Ebola cases,” said Khan.

He also said that international travel restrictions on countries with high rates of Ebola could have economic, health and humanitarian consequences that could compromise efforts to control the outbreak.

“There is a great danger that excessive travel restrictions could disrupt supply chains of necessary food, people, medicine and equipment to help fight the epidemic and cause severe economic hardship.” 

The 2005 International Health Regulations, signed by 196 countries, specify that steps to control the international spread of diseases should “avoid unnecessary interference with international traffic and trade.”

Khan said that supporting humanitarian aid, increasing the number of health care workers, and providing logistical support and equipment would be the most effective way to prevent the international spread of Ebola from West Africa. In addition, focusing on “exit screening” travelers as they leave affected countries would be more efficient than “entry screening” as they arrive in cities around the world.

Khan said that while a number of countries, including Canada, the United States and England are implementing entry screening by far the most efficient approach is exit screening of passengers leaving the three West African countries that are affected by Ebola – as recommended by the World Health Organization.

Exit screening is a preventative measure and can be focused on three major international airports in affected countries, whereas entry screening would require far greater resources to implement. Entry screening may detract resources from other important public health activities in countries with limited public health infrastructure, he said.

Leslie Shepherd is a writer with St. Michael's Hospital, a partner of the University of Toronto. (.)