A couple in protective masks walk in the western Ukrainian city of Lviv, Tuesday, Nov. 3, 2009. Russia and Slovakia tightened their borders with Ukraine on Tuesday as the World Health Organization began investigating a suspected swine flu outbreak. In the western city of Lviv, the government has urged cafes, cinemas and theaters to close indefinitely, and roughly a third of the people in the streets on Tuesday wore surgical masks to avoid inhaling the virus.