(CBS) — A strain of the swine flu is rapidly spreading throughout the Chicago area.

More than 20 of the H1N1 cases have been detected at Loyola University Medical Center in recent days, including five on Christmas Eve.

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Now, CBS 2 has learned, another 41 cases have turned up at the University of Chicago Medical Center. Doctors say there have been eight cases in just the week before Christmas.

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Meanwhile, at hospitals in the Advocate Health network, 90 percent of the confirmed flu cases have turned out to be H1N1.

The Centers for Disease Control says it could be as dangerous as the 2009 swine flu outbreak.

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Doctors say this year’s flu vaccine protects against the H1N1 strain of the flu and they have plenty of vaccines on hand.