What kind of viral infection would cause these symptons in a 17 year old.she has backache,headach,tenderness?

in her right side,nauseu ,feever of 101,she was addmitted in the hospital they have ran test on her vital oragans all check out fine,they have checked her for drugs and none are found.they checked for food poisoning, and she is not pregnant,nor is she diabatic,they doctors are puzzled,there running more test today,her gall bladder is fine ,phyisically she is fine.as far as her major organs , her blood pressure is good and her heart rate is good,so can someone help me out here and tell me,while im sitting here waiting on these doctors to find out what is wrong with my child,does any one have any knowladge of what this is,?