The upshot is, by the time you are actually contagious, you're so sick you're at home in bed, not mixing it up with other people and infecting them. By the time you're well enough again from the initial onslaught, the pustules have begun to appear and unless you've been living on another planet and haven't heard about the possible threat, then you're going to know not to go around exposing people.
My poor pharmicist friend blows a gasket just about every time the news even so much as mentions smallpox because they mangle the actual facts of the disease beyond recognition just to stir up the panic.
-penny
check out post # 139 and see specifically this:
Virus titers in saliva are highest the first week of infection, but infectivity can last up to 3 weeks (until the scabs fall off).
The pox and scabs that occur later are most infectious because they are the most concentrated. But it is also in the saliva and those levels are highest at asymptomatic times.