What Causes Cough,voice Hoarseness And Raise In Body Temperature ?

3 year old has had a fever since Saturday, which is 5 days. Some but very little coughing. Not much of an appetite. Voice sounds hoarse but no other obvious symptoms of congestion. Tested negative on Monday for strep and an ear infection. On Monday, no fluid in the lungs. Still has fever, goes down with motrin, goes up to about 100.5 or so before afternoon dose. Slept thru the night but woke up hot and screaming Tuesday night.
HELP?