Ebola-affected countries should immediately begin exit screening all passengers leaving international airports, sea ports and major ground crossings, the UN health agency urged yesterday.

The risk of the Ebola virus being transmitted during air travel is low because, unlike infections such as influenza or tuberculosis, it is not spread by breathing air and airborne particles from an infected person.

Nonetheless, the World Health Organisation said anyone thought to have the virus should not be allowed to travel and all passengers should routinely wash their hands and avoid direct contact with body fluids of infected people.

"Transmission requires direct contact with blood, secretions, organs or other body fluids of infected living or dead persons or animals, all unlikely exposures for the average traveller," the agency said in a statement. "There should be no international travel of Ebola contacts or cases, unless the travel is part of an appropriate medical evacuation."

The only way to contain the disease, for which there is no licensed treatment, is by isolating the sick and closely watching for signs of infection in those they have come into contact with.

All countries, even those unaffected by the Ebola outbreak in West Africa, need to strengthen their ability to detect and immediately contain new cases without doing anything that unnecessarily interferes with international travel or trade, the agency said.

Irish Independent