eMedicine Specialties > Pediatrics: General Medicine > Infectious Disease

Influenza: Differential Diagnoses & Workup

Author: Hakan Leblebicioglu, MD, Chairman, Professor, Department of Infectious Diseases and Clinical Microbiology, Ondokuz Mayis University Medical School, Turkey
Coauthor(s): Itzhak Brook, MD, MSc, Professor, Department of Pediatrics, Georgetown University School of Medicine
Contributor Information and Disclosures

Updated: Aug 11, 2009

Differential Diagnoses

Chlamydial Infections
Mycoplasma Infections
Pharyngitis
Pneumonia
Q Fever
Respiratory Syncytial Virus Infection

Workup

Laboratory Studies

  • Isolation of influenza viruses or detection of viral antigens in respiratory secretions (eg, throat swabs, nasopharyngeal washes, sputum) can be performed during acute influenza infection. Cultures should be obtained within 3 days of onset of illness.
  • The type of influenza virus (A or B) may be determined by immunofluorescence or hemagglutination inhibition (HAI) techniques, and the hemagglutinin subtypes of influenza A virus (H1, H2, H3) may be identified using HAI with subtype-specific antisera.
  • Complement-fixation (CF) and hemagglutination inhibition (HI) tests are the most common methods used to compare sera in persons with acute and convalescent infection, although these tests have low sensitivity and specificity. Rises in immunoglobulin (Ig) titer of at least 4 fold are considered diagnostic of infection. Significant rises as measured by enzyme-linked immunosorbent assay (ELISA) are diagnostic of acute infection.
  • Viral antigens in respiratory secretions can be detected by immunofluorescence (IF) assay, time-resolved immunofluorescence assay (TRIFA), radioenzyme immunoassay, and ELISA. ELISA results can be obtained within 1 hour.
  • Recently, rapid diagnostic testing for influenza A antigen has become available and should allow clinicians to assess the need for antiviral use in patients with influenza A infection in a timelier manner.
  • Polymerase chain reaction (PCR) can be used to detect influenza virus RNA in respiratory secretions.

Imaging Studies

  • Chest radiography may be necessary to exclude the diagnosis of pneumonia.

More on Influenza

Overview: Influenza
Differential Diagnoses & Workup: Influenza
Treatment & Medication: Influenza
Follow-up: Influenza
References
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References

  1. HHS Declares Public Health Emergency for Swine Flu. US Department of Health and Human Resources. Available at http://www.hhs.gov/news/press/2009pres/04/20090426a.html. Accessed April 27, 2009.

  2. Swine Influenza (Flu). Centers for Disease Control and Prevention. Available at http://www.cdc.gov/swineflu/. Accessed April 27, 2009.

  3. Emergence of a Novel Swine-Origin Influenza A (H1N1) Virus in Humans. N Engl J Med. Jun 3 2009;[Medline].

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  5. Guidance for Clinicians and Public Health Professionals. Centers for Disease Control and Prevention. Available at http://www.cdc.gov/swineflu/guidance/. Accessed April 27, 2009.

  6. [Best Evidence] Tappenden P, Jackson R, Cooper K, et al. Amantadine, oseltamivir and zanamivir for the prophylaxis of influenza (including a review of existing guidance no. 67): a systematic review and economic evaluation. Health Technol Assess. Feb 2009;13(11):iii, ix-xii, 1-246. [Medline].

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  8. [Guideline] Fiore AE, Shay DK, Broder K, Iskander JK, Uyeki TM, Mootrey G, et al. Prevention and control of seasonal influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009. MMWR Recomm Rep. Jul 31 2009;58:1-52. [Medline]. [Full Text].

  9. American Academy of Pediatrics Committee on Infectious Diseases. Prevention of influenza: recommendations for influenza immunization of children, 2007-2008. Pediatrics. Apr 2008;121(4):e1016-31. [Medline].

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Further Reading

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Keywords

influenza, flu, swine flu, swine influenza, H1N1, grip, grippe, acute catarrhal fever, respiratory infection, upper respiratory tract infection, viral infection, severe acute respiratory syndrome, SARS, pharyngitis, rhinitis, cervical lymphadenopathy, conjunctivitis, coup, pneumonia, chronic respiratory disease, chronic cardiac disease, chronic renal failure, diabetes mellitus, immunosuppression, treatment, diagnosis

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Contributor Information and Disclosures

Author

Hakan Leblebicioglu, MD, Chairman, Professor, Department of Infectious Diseases and Clinical Microbiology, Ondokuz Mayis University Medical School, Turkey
Hakan Leblebicioglu, MD is a member of the following medical societies: American Society for Microbiology
Disclosure: Nothing to disclose.

Coauthor(s)

Itzhak Brook, MD, MSc, Professor, Department of Pediatrics, Georgetown University School of Medicine
Itzhak Brook, MD, MSc is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians-American Society of Internal Medicine, American Federation for Clinical Research, American Medical Association, American Society for Microbiology, Armed Forces Infectious Diseases Society, Association of Military Surgeons of the US, Infectious Diseases Society of America, International Immunocompromised Host Society, International Society for Infectious Diseases, Medical Society of the District of Columbia, New York Academy of Sciences, Pediatric Infectious Diseases Society, Society for Ear, Nose and Throat Advances in Children, Society for Experimental Biology and Medicine, Society for Pediatric Research, Southern Medical Association, and Surgical Infection Society
Disclosure: Nothing to disclose.

Medical Editor

David Jaimovich, MD, Chief Medical Officer, Joint Commission International and Joint Commission Resources
David Jaimovich, MD is a member of the following medical societies: American Academy of Pediatrics
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

Leslie L Barton, MD, Professor, Program Director, Department of Pediatrics, University of Arizona School of Medicine
Leslie L Barton, MD is a member of the following medical societies: American Academy of Pediatrics, Association of Pediatric Program Directors, Infectious Diseases Society of America, and Pediatric Infectious Diseases Society
Disclosure: Nothing to disclose.

CME Editor

Robert W Tolan Jr, MD, Chief, Division of Allergy, Immunology and Infectious Diseases, The Children's Hospital at Saint Peter's University Hospital; Clinical Associate Professor of Pediatrics, Drexel University College of Medicine
Robert W Tolan Jr, MD is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, American Society for Microbiology, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, Phi Beta Kappa, and Physicians for Social Responsibility
Disclosure: GlaxoSmithKline Honoraria Speaking and teaching; MedImmune Honoraria Speaking and teaching; Merck Honoraria Speaking and teaching; sanofi pasteur Honoraria Speaking and teaching; Baxter Healthcare Honoraria Speaking and teaching

Chief Editor

Russell W Steele, MD, Head, Division of Pediatric Infectious Diseases, Ochsner Children's Health Center; Clinical Professor, Department of Pediatrics, Tulane University School of Medicine
Russell W Steele, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Immunologists, American Pediatric Society, American Society for Microbiology, Infectious Diseases Society of America, Louisiana State Medical Society, Pediatric Infectious Diseases Society, Society for Pediatric Research, and Southern Medical Association
Disclosure: None None None

 
 
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