If I remember the book correctly, Robert Preston explained why a really hideous disease could not spread too far. Such a virus is too efficient. It kills of its host before the host has much contact with others. Very often, for the disease to spread very far, it would become less lethal.
He also brought out the problem with plane travel. Take a plane full of people who become infected on the way from Africa to Rome, for instance. Those people then get on other planes. Within one day, that virus could spread all over the world.
My concern, which doesn't seem to get an answer, is what happens if SARS starts spreading in countries where health and sanitary services have been affected by war? What if this thing gets into refugee camps? What if soldiers get it? Will they be quarantined where they are? If this were to start spreading in Afghanistan and Iraq, what could possibly be done?
I really hope someone has contingency plans if this did occur.