Influenza Differential Diagnoses

  • Author: Robert W Derlet, MD; Chief Editor: Burke A Cunha, MD   more...
 
Updated: Mar 8, 2012
 
 

Diagnostic Considerations

Accurately diagnosing influenza A or B infection based solely on clinical criteria is difficult because of the overlapping symptoms caused by the various viruses associated with upper respiratory tract infection (URTI). In addition, several serious viruses, including adenoviruses, enteroviruses, and paramyxoviruses, may initially cause influenzalike symptoms.

The early presentation of mild or moderate cases of flavivirus infections (eg, dengue) may initially mimic influenza. For example, some cases of West Nile fever acquired in New York in 1999 were clinically misdiagnosed as influenza.

Like influenza, URTIs from these viruses are more common in the winter. As a result, during the winter, clinics and emergency department waiting rooms fill with patients who have influenza or other URTIs.

Influenza pneumonia must be differentiated from other forms of viral pneumonia, bacterial pneumonia, and noninfectious causes of respiratory distress, such as congestive heart failure (CHF), chronic obstructive pulmonary disease (COPD), pulmonary edema, and aspiration pneumonitis.

Avian influenza

Risk factors or features that should raise the index of suspicion include the following:

  • Travel to (within the last 2 wk) or location in a country with known avian influenza cases in animals or humans
  • Unusual comorbidities such as encephalopathy or diarrhea
  • History of exposure to birds, especially living in close proximity to birds, contact with sick or dying birds, or consumption of incompletely cooked bird meat
  • History of exposure to individuals with known avian influenza, especially family, or to sick people in a country with known human cases of avian influenza

The situation can be complicated during outbreaks of severe respiratory disease not due to avian influenza. The first case of laboratory-confirmed avian influenza infection was documented during the severe acute respiratory syndrome (SARS) outbreak and was mistakenly misdiagnosed as SARS.[4]

Although a small percentage overall, several cases in which respiratory disease was limited or not apparent (with even normal chest radiography findings) have been described.[26] The primary presenting illness has been encephalitis and/or diarrhea.

Differential Diagnoses

Proceed to Workup
 
 
Contributor Information and Disclosures
Author

Robert W Derlet, MD  Professor of Emergency Medicine, University of California at Davis School of Medicine; Chief Emeritus, Emergency Department, University of California at Davis Health System

Robert W Derlet, MD is a member of the following medical societies: American Academy of Emergency Medicine, American Association for the Advancement of Science, Infectious Diseases Society of America, Society for Academic Emergency Medicine, and Wilderness Medical Society

Disclosure: Nothing to disclose.

Coauthor(s)

Nicholas John Bennett, MB, BCh, PhD,  Assistant Professor in Pediatrics, Division of Infectious Diseases, Connecticut Children's Medical Center

Nicholas John Bennett, MB, BCh, PhD, is a member of the following medical societies: Alpha Omega Alpha and American Academy of Pediatrics

Disclosure: Nothing to disclose.

Ethan E Bodle, MD, MPH  Associate Physician, Department of Emergency Medicine, Kaiser Permanente East Bay Medical Center

Ethan E Bodle, MD, MPH is a member of the following medical societies: American College of Emergency Physicians and American Public Health Association

Disclosure: Nothing to disclose.

Joseph Domachowske, MD  Professor of Pediatrics, Microbiology and Immunology, Department of Pediatrics, Division of Infectious Diseases, State University of New York Upstate Medical University

Joseph Domachowske, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American Society for Microbiology, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, and Phi Beta Kappa

Disclosure: Nothing to disclose.

Jon Mark Hirshon, MD, MPH  Associate Professor, Department of Emergency Medicine, University of Maryland School of Medicine

Jon Mark Hirshon, MD, MPH is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, American Public Health Association, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Edmond A Hooker II, MD, DrPH, FAAEM  Assistant Professor, Department of Emergency Medicine, University of Cincinnati College of Medicine; Associate Professor, Department of Health Services Administration, Xavier University

Edmond A Hooker II, MD, DrPH, FAAEM is a member of the following medical societies: American Academy of Emergency Medicine, American Public Health Association, Society for Academic Emergency Medicine, and Southern Medical Association

Disclosure: Nothing to disclose.

Hien H Nguyen, MD, MS  Associate Clinical Professor, Division of Infectious Diseases and Pulmonary/Critical Care Medicine, Infectious Diseases Consultant and Hospitalist, University of California, Davis, Health System; Medical Director, Acute Infections Management Service, Antimicrobial Infusion Service; Medical Director, Electronic Health Records of University of California, Davis, Health System

Hien H Nguyen, MD, MS is a member of the following medical societies: American College of Physicians, Infectious Diseases Society of America, and Society of Critical Care Medicine

Disclosure: Nothing to disclose.

Frederick Burton Rose, MD, FACP  Professor, Department of Medicine, University Hospital Epidemiologist, State University of New York Upstate Medical University

Frederick Burton Rose, MD, FACP is a member of the following medical societies: American College of Physicians and Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Christian E Sandrock, MD, MPH, FCCP  Associate Professor of Clinical Medicine, Division of Pulmonary/Critical Care Medicine, Division of Infectious Diseases, Department of Internal Medicine, University of California, Davis Medical Center

Christian E Sandrock, MD, MPH, FCCP is a member of the following medical societies: American College of Chest Physicians, American Thoracic Society, and Infectious Diseases Society of America

Disclosure: Pfizer Honoraria Speaking and teaching; Pfizer Honoraria Consulting; therevance Honoraria Consulting; GSK Honoraria Speaking and teaching

David Yew, MD  Assistant Clinical Professor, Department of Surgery, University of Hawaii, John A Burns School of Medicine; Medical Director and Flight Physician, Hawaii Life Flight, AirMed International

David Yew, MD is a member of the following medical societies: Air Medical Physician Association and American College of Emergency Physicians

Disclosure: Nothing to disclose.

Specialty Editor Board

Klaus-Dieter Lessnau, MD, FCCP  Clinical Associate Professor of Medicine, New York University School of Medicine; Medical Director, Pulmonary Physiology Laboratory; Director of Research in Pulmonary Medicine, Department of Medicine, Section of Pulmonary Medicine, Lenox Hill Hospital

Klaus-Dieter Lessnau, MD, FCCP is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Medical Association, American Thoracic Society, and Society of Critical Care Medicine

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Joseph F John Jr, MD, FACP, FIDSA, FSHEA  Clinical Professor of Medicine, Molecular Genetics and Microbiology, Medical University of South Carolina College of Medicine; Associate Chief of Staff for Education, Ralph H Johnson Veterans Affairs Medical Center

Disclosure: Nothing to disclose.

Charles V Sanders, MD  Edgar Hull Professor and Chairman, Department of Internal Medicine, Professor of Microbiology, Immunology and Parasitology, Louisiana State University School of Medicine at New Orleans; Medical Director, Medicine Hospital Center, Charity Hospital and Medical Center of Louisiana at New Orleans; Consulting Staff, Ochsner Medical Center

Charles V Sanders, MD is a member of the following medical societies: Alliance for the Prudent Use of Antibiotics, Alpha Omega Alpha, American Association for the Advancement of Science, American Association of University Professors, American Clinical and Climatological Association, American College of Physician Executives, American College of Physicians, American Federation for Medical Research, American Foundation for AIDS Research, American Geriatrics Society, American Lung Association, American Medical Association, American Society for Microbiology, American Thoracic Society, American Venereal Disease Association, Association for Professionals in Infection Control and Epidemiology, Association of American Medical Colleges, Association of American Physicians, Association of Professors of Medicine, Infectious Disease Society for Obstetrics and Gynecology, Infectious Diseases Society of America, Louisiana State Medical Society, Orleans Parish Medical Society, Royal Society of Medicine, Sigma Xi, Society of General Internal Medicine, Southeastern Clinical Club, Southern Medical Association, Southern Society for Clinical Investigation, and Southwestern Association of Clinical Microbiology

Disclosure: Nothing to disclose.

Chief Editor

Burke A Cunha, MD  Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital

Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Additional Contributors

The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous author Ruth Lawrence, MD, to the development and writing of the source article.

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Chest radiograph of severe lung disease in a patient with avian influenza.
Global map of countries where avian influenza (bird and human infections) has been reported. Image courtesy of PandemicFlu.gov.
Colorized transmission electron micrograph shows avian influenza A H5N1 viruses (gold) grown in MDCK cells (green). Image courtesy of Centers for Disease Control and Prevention.
Transmission electron micrograph (original magnification 150,000X) shows ultrastructural details of an avian influenza A (H5N1) virion, a subtype of avian influenza A. Note the stippled appearance of the roughened surface of the proteinaceous coat encasing the virion. Image courtesy of Centers for Disease Control and Prevention.
Photograph shows police officers during the 1918 Spanish flu pandemic. Image courtesy of US National Archives.
Avian H5N1 influenza in humans, annual case counts from the World Health Organization.
 
 
 
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