Bird Flu (H5N1)

Overview – Bird Flu (H5N1)

Bird flu, or avian influenza (H5N1), is a rare but severe viral respiratory infection transmitted from birds to humans. It carries a high mortality rate and poses a significant public health risk due to its potential for pandemic spread. Prompt identification, antiviral therapy, and public health containment measures are critical for managing suspected cases.

Definition

Bird flu refers to human infection with the H5N1 strain of avian influenza virus, a zoonotic virus primarily affecting birds but capable of infecting humans through close contact.

Aetiology

• Influenza A H5N1 virus
  • Highly pathogenic avian influenza (HPAI) strain
  • Primarily affects poultry and wild birds

Pathogenesis

• Transmission:
  • Direct contact with infected birds or contaminated environments
  • Aerosol transmission in rare cases
• Incubation period: 2–8 days
• Mechanism:
  • Viral replication in human respiratory epithelium
  • Epithelial dysfunction → severe inflammation
• Mortality rate: ~63%

Clinical Features

Symptoms

• High fever (>38°C)
• Headache
• Myalgia
• Cough (± sputum)
• Dyspnoea
• Sore throat or gastrointestinal symptoms may be present

Signs

• Respiratory distress
• Pneumonia with radiological infiltrates
• Tachypnoea, tachycardia
• Rapid progression to:
  • Acute Respiratory Distress Syndrome (ARDS)
  • Multi-organ failure
  • Death

Investigations

• Nasopharyngeal aspirate (NPA) for PCR testing
• CXR:
  • Pulmonary infiltrates
  • ± Pleural effusion
• Bloods:
  • Lymphopenia, raised inflammatory markers

Management

• ICU admission for severe cases
• Supportive care:
  • Mechanical ventilation for ARDS
  • IV fluids, organ support
• Antiviral therapy:
  • Oseltamivir (Tamiflu®)
  • Zanamivir (Relenza®)
  • Most effective if started within 48 hours of symptom onset

Prevention

• No current licensed vaccine for H5N1 in humans
• Preventative strategies:
  • Hygiene measures (handwashing, PPE)
  • Avoid contact with live birds or bird markets
  • Notify public health authorities for any suspected case
  • Post-exposure prophylaxis: Oseltamivir or Zanamivir
  • Contact tracing and quarantine of exposed individuals

Summary – Bird Flu (H5N1)

Bird flu (H5N1) is a highly virulent avian influenza infection that causes severe pneumonia and multi-organ failure with high mortality. Early diagnosis, ICU support, and antiviral therapy are essential. Vigilant public health measures are necessary to prevent transmission. For broader context, visit our Respiratory Overview page.