title: Clinical Mimics: An Emergency Medicine-Focused Review of Influenza Mimics.
abstract: BACKGROUND
  Influenza viruses are a significant cause of morbidity and mortality in the United States. Given the wide range of symptoms, emergency physicians must maintain a broad differential diagnosis in the evaluation and treatment of patients presenting with influenza-like illnesses.
  
  
  OBJECTIVE
  This review addresses objective and subjective symptoms commonly associated with influenza and discusses important mimics of influenza viruses, while offering a practical approach to their clinical evaluation and treatment.
  
  
  CONCLUSIONS
  Influenza-like symptoms are common in the emergency department (ED), and influenza accounts for > 200,000 hospitalizations annually. The three predominant types are A, B, and C, and these viruses are commonly transmitted through aerosolized viral particles with a wide range of symptoms. The most reliable means of identifying influenza in the ED is rapid antigen detection, although consideration of local prevalence is required. High-risk populations include children younger than 4 years, adults older than 50 years, adults with immunosuppression or chronic comorbidities, pregnancy, obesity, residents of long-term care facilities, and several others. The Centers for Disease Control and Prevention recommends treatment with neuraminidase inhibitors in these populations. However, up to 70% of patients with these symptoms may have a mimic. These mimics include infectious and noninfectious sources. The emergency physician must be aware of life-threatening mimics and assess for these conditions while beginning resuscitation and treatment.
  
  
  CONCLUSIONS
  The wide range of symptoms associated with influenza overlap with several life-threatening conditions. Emergency physicians must be able to rapidly identify patients at risk for complications and those who require immediate resuscitation.
authors.affiliation: Department of Emergency Medicine, San Antonio Military Medical Center, Fort Sam Houston, Texas.
authors.forename: Erica
authors.initials: E
authors.lastname: Simon
authors.affiliation: Department of Emergency Medicine, San Antonio Military Medical Center, Fort Sam Houston, Texas.
authors.forename: Brit
authors.initials: B
authors.lastname: Long
authors.affiliation: Department of Emergency Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Alex
authors.initials: A
authors.lastname: Koyfman
mesh_terms: D000146:Acids, Carbocyclic; D000368:Aged; D000369:Aged, 80 and over; D000998:Antiviral Agents / Q000494:pharmacology / Q000627:therapeutic use; D002675:Child, Preschool; D003517:Cyclopentanes / Q000494:pharmacology / Q000627:therapeutic use; D004635:Emergency Medicine / Q000193:education*; D006146:Guanidines / Q000494:pharmacology / Q000627:therapeutic use; D006801:Humans; D007223:Infant; D007251:Influenza, Human / Q000175:diagnosis* / Q000188:drug therapy; D008875:Middle Aged; D053139:Oseltamivir / Q000494:pharmacology / Q000627:therapeutic use; D012307:Risk Factors; D014481:United States; D053243:Zanamivir / Q000494:pharmacology / Q000627:therapeutic use
chemical_list: D000146:Acids, Carbocyclic; D000998:Antiviral Agents; D003517:Cyclopentanes; D006146:Guanidines; D053139:Oseltamivir; D053243:Zanamivir; C414210:peramivir
keywords: influenza; mimic; upper respiratory infection; viral illness; viral syndrome