Commuters wear masks as a precaution against flu while riding a bus in the western Ukrainian city of Lviv, Wednesday, Nov. 4, 2009. Russia and Slovak

Commuters wear masks as a precaution against flu while riding a bus in the western Ukrainian city of Lviv, Wednesday, Nov. 4, 2009. Russia and Slovakia have tightened their borders with Ukraine as the World Health Organization began investigating a suspected swine flu outbreak. The European Union says it is coordinating closely with health experts in Ukraine to help it cope with a suspected swine flu outbreak. (AP Photo/Sergei Grits)

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