The confirmed case is a man in the Philadelphia suburbs who's since fully recovered.
Planners say the worst-case scenario is a pandemic outbreak that would affect up to 40 percent of the state's residents.
The confirmed case was in Montgomery County.
The probable cases are in Allegheny, Bucks, Cambria, Chester, Franklin, Lehigh, Luzerne, Lycoming, Montgomery, Philadelphia and York counties.
RELATED INFORMATION:
FAQs about swine flu
Additional swine flu resources
Transcript of 6abc.com's swine flu chat with local experts
RELATED LINKS:
CDC Swine Flu site
World Health Organization
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Swine flu cases around the world
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