Steroids, like prednisone, can mask an infection. If it keeps up, can they do blood cultures, urine and stool samples to check for one. It may be worth asking.
From Rxlist.com under drug warnings.
http://www.rxlist.com/deltasone-drug.htm
" Corticosteroids may mask some signs of infection, and new infections may appear during their use. Infections with any pathogen including viral, bacterial, fungal, protozoan or helminthic infections, in any location of the body, may be associated with the use of corticosteroids alone or in combination With other immunosuppressive agents that affect cellular immunity, humoral immunity, or neutrophil function."