paragraph: A flight from Los Angeles to Nashville is diverted to land in Las Vegas , Nevada when one of the passengers , Ralph Bundt becomes violent and attacks a stewardess . Ralph had been bitten by a hamster Which is really a lab rat , brought onto the plane by Henry for his school students . Ralph is restrained , but not before he bites the flight attendant Paula . The plane is forced to make an emergency landing in Las Vegas , and once it has landed , air traffic control refuses to let it approach the gate . Disobeying orders , Captain Forrest and his co-pilot Willsy find a jetway operated by a baggage handler Ed Ramirez . Almost everyone evacuates the plane , except for the elderly couple Bev Stevens and her paralyzed mute husband Doc Stevens , and the pilots , who try to keep the violent Ralph contained in an aircraft bathroom . However , they learn that they have been locked out of the airport . Soon , armed soldiers and what appear to be CDC scientists surround the terminal . One of the passengers , a military medic named Shilah Washington , reveals she has a medical kit in her bag in the plane's cargo hold . The lead flight attendant Jenny , Henry , Ed , Nial Britz , and Preston sneak back into the plane to retrieve it . They retrieve Shilah's kit and Nial's gun and they try to leave the hold . While in the plane , Jenny is attacked by an infected Captain Forrest and Nial shoots and kills him , but it seems that some of the captain's blood had gotten into Nial's eye . 
question: What causes Ralph to bite the flight attendant?
answer: Bitten by hamster