Avian Influenza (Bird Flu) Clinical Presentation

Updated: Feb 12, 2020
  • Author: Nicholas John Bennett, MBBCh, PhD, FAAP, MA(Cantab); Chief Editor: Michael Stuart Bronze, MD  more...
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The key history component that should prompt consideration of avian influenza as a possible diagnosis is exposure to sick, dead, or dying poultry or humans with avian influenza. Many cases involve close contact, such as plucking or gutting of dead birds, removing infected carcasses, or ingesting incompletely cooked bird meat or blood. Some cases have had no link to prior exposure to sick birds, suggesting that spread from asymptomatic birds is possible or that the virus can be transmitted environmentally on fomites.

The time from exposure to disease is slightly longer than in human influenza, although this interval can be as short as 2 days. Intervals of up to 17 days have been reported, although most cases occur within one week of exposure. [14]

Respiratory symptoms are the most common presentation. More severe respiratory distress occurs around 5 days from the initial symptoms. The sputum is sometimes bloody.

Other symptoms include the following:

  • Fever (temperature >38°C)
  • Diarrhea (watery, nonbloody) (possibly a poor prognostic sign)
  • Vomiting
  • Chest and/or abdominal pain
  • Encephalitis (Two persons in Vietnam presented with encephalitis only. [14] )

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 SARS outbreak and was mistakenly misdiagnosed as SARS.

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. [14] The primary presenting illness has been encephalitis and/or diarrhea.


Physical Examination

Tachypnea and crackles are common.

Wheeze is occasionally apparent.

Conjunctival suffusion/conjunctivitis is not uncommon.

Case reports have described other occasional signs (eg, bleeding gums, always in the presence of viral pneumonia). [14]