Khloe Kardashian contracted a serious staph infection at the hospital where Lamar Odom is laid up, and it's so bad she's had to cancel a portion of her book tour.

Lamar has been hospitalized at Cedars-Sinai Medical Center in L.A. for a month, and Khloe has been a frequent visitor.

We're told Khloe has a lesion on her leg which became incredibly painful. She developed a high fever, swollen glands. She's also sweating profusely with intermittent chills.