Under the rules of the Southern African Customs Union, a fledgling free-trade area, cars made in Botswana can be exported to South Africa almost duty-free.

ECONOMIST: The desert booms

But Domingo Cavallo, Argentina's new economy minister, has talked (though not publicly) of Mercosur scrapping its customs union, and becoming simply a free-trade area.

ECONOMIST: Another blow to Mercosur

Already at various border crossing points, customs authorities are having people who appear sick taken to a secondary inspection area for further evaluation.

CNN: Commentary: Flu shouldn't close Mexico border