Katy Perry & Pals Catch Bieber Fever!

Katy Perryseems to have caught a serious case of Justin Bieber's concert at the Staples Center in Los Angeles.

K-Pez tweeted: "Last night I saw The Black Keys, tonight I saw Bieber. I think my musical week is complete."

The 27-year old then added: "WE ARE BELIEBERS!", accompanying the post with a picture of herself and a group of friend's wearing purple hoodies, which are heavily associated with the Boyfriend hitmaker.

Earlier this week, Justin was forced to apologise to fans after vomiting on stage during his Believe show in Glendale, Arizona - blaming his sickness on a lethal mixture of spaghetti and milk.

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