Systemic infection Bacterial Bacteremia Group A streptococcus infection (pharyngitis, scarlet fever) Brucellosis Leptospirosis Tularemia Viral Epstein–Barr virus Cytomegalovirus Human immunodeficiency virus Adenovirus Varicella Rubella Rubeola (measles) Hepatitis B virus Fungal Histoplasmosis Coccidioidomycosis Blastomycosis Parasitic Toxoplasmosis Malaria Spirochete Syphilis Lyme disease Autoimmune disease Juvenile idiopathic arthritis Systemic lupus erythematosus Dermatomyositis Serum sickness Drug reaction with eosinophilia and systemic symptoms (DRESS) Autoimmune hemolytic anemia Chronic granulomatous disease (sarcoid) Malignancy Leukemia (acute lymphoblastic or acute myelogenous leukemia) Non-Hodgkin lymphoma Hodgkin lymphoma Neuroblastoma Histiocytosis Hemophagocytic lymphohistiocytosis (HLH)