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Avian influenza A (H5N1) virus infection

Last reviewed: 1 Aug 2025
Last updated: 11 Feb 2025

Summary

Definition

History and exam

Key diagnostic factors

  • cough
  • influenza-like illness
  • conjunctivitis
  • dyspnea
  • fever
  • rales, rhonchi
  • wheeze
  • decreased breath sounds
  • tachypnea
Full details

Other diagnostic factors

  • abdominal pain, vomiting, diarrhea
  • altered mental status
  • seizures
Full details

Risk factors

  • close contact with infected birds or poultry
  • close contact with infected animals or mammals
  • recent travel to a country with H5N1 virus outbreaks
  • environmental exposure to H5N1 virus
  • close contact with infected humans
  • laboratory work with H5N1 virus
Full details

Diagnostic tests

1st tests to order

  • CBC with differential
  • LFTs
  • chest x-ray
  • pulse oximetry
  • sputum Gram stain
  • sputum and blood bacterial culture
  • real-time reverse transcription polymerase chain reaction (rtRT-PCR)
Full details

Tests to consider

  • viral culture
Full details

Treatment algorithm

INITIAL

close contact of confirmed or probable case

ACUTE

suspected or probable or confirmed infection

Contributors

Authors

Timothy M. Uyeki, MD, MPH, MPP

Chief Medical Officer

Influenza Division

National Center for Immunization and Respiratory Diseases

Centers for Disease Control and Prevention

Atlanta

GA

Disclosures

TMU declares that he is an unpaid member and clinical Chair of the World Health Organization Guidelines Developmental Group: Clinical Management of Influenza Guidelines 2023-2024.

Acknowledgements

Dr Timothy M. Uyeki would like to gratefully acknowledge Dr Justin R. Ortiz, a previous contributor to this topic.

Disclosures

JRO declares that he has no competing interests.

Peer reviewers

Richard Martinello, MD

Professor

Departments of Internal Medicine and Pediatrics

Yale School of Medicine

New Haven

CT

Disclosures

RM declares that he has no competing interests.

An De Sutter, MD, PhD

Associate Professor

Department of General Practice and Primary Health Care

Ghent University

Belgium

Disclosures

ADS declares that she has no competing interests.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

Centers for Disease Control and Prevention. Interim guidance on the use of antiviral medications for treatment of human infections with novel influenza A viruses associated with severe human disease. Sep 2024 [internet publication].Full text

Centers for Disease Control and Prevention. Highly pathogenic avian influenza A(H5N1) virus: interim recommendations for prevention, monitoring, and public health investigations. Dec 2024 [internet publication].Full text

Centers for Disease Control and Prevention. Interim guidance on specimen collection and testing for patients with suspected infection with novel influenza A viruses associated with severe disease or with the potential to cause severe disease in humans. Sep 2024 [internet publication].Full text

World Health Organization. Clinical practice guidelines for influenza. Sep 2024 [internet publication].Full text

Centers for Disease Control and Prevention. Interim guidance for follow-up of close contacts of persons infected with novel influenza A viruses associated with severe human disease or with potential to cause severe human disease, and use of antiviral medications for post-exposure prophylaxis. Aug 2024 [internet publication].Full text

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.
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