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Understanding Highly Pathogenic Avian Influenza (HPAI) and Minimizing Transmission Risk
Commentary05/30/24 Dr. Laurie Hess, DVM, DABVP (Avian Practice), Editor-in-Chief, The Veterinary Manuals

Understanding Highly Pathogenic Avian Influenza (HPAI) and Minimizing Transmission Risk

Since January 2022, highly pathogenic avian influenza (HPAI) has been spreading across North America, affecting both wild birds and poultry flocks. As of May 2024, over 92 million HPAI cases have been reported in poultry and nearly 10,000 cases in wild birds in the US, with the virus confirmed in every state except Hawaii. This outbreak has also led to cases in mammals, including humans. Recently, there has been reported transmission from infected poultry to other animals (such as goats, cattle, and cats) and to humans in direct contact with these animals. However, signs in infected humans have been mild and self-limiting. Understanding the nature of the virus and implementing preventive measures is crucial in combating its spread.

Key Facts about HPAI:

  • HPAI is an influenza A virus, classified by surface protein variants.
  • The current outbreak involves the H5N1 strain, with an HA 5 protein and an NA 1 protein.
  • The virus is highly transmissible and durable in the environment, surviving for extended periods in water and feces.
  • Birds, especially waterfowl, are the primary carriers and transmitters of HPAI, with minimal clinical signs.
  • HPAI causes severe disease in infected birds, with high mortality rates.

Recognizing and Addressing HPAI:

  • Veterinarians treating wild and outdoor companion birds are most likely to encounter HPAI cases.
  • Awareness of HPAI outbreaks in the area is essential, with regular updates from the CDC.
  • Screening patients using prioritized biosecurity measures based on exposure risk is crucial.
  • Infected poultry may show respiratory distress, lethargy, neurologic signs, and sudden death.
  • Examination of outdoor birds should be conducted in isolation, with thorough disinfection protocols.
  • Indoor birds may be at lower risk but should be evaluated based on owner's exposure to outdoor birds.

Reducing Transmission Risk:

  • When handling suspected cases, use of personal protective equipment is essential, including masks, gloves, and gowns.
  • Proper disinfection of facilities and equipment after each examination is crucial.
  • Timely examination of outdoor birds and minimizing environmental viral particle survival is recommended.

Highly pathogenic avian influenza (HPAI) primarily affects birds and is not easily transmitted to humans. However, in some cases, human infection with HPAI strains has occurred. Notably, human infections with HPAI are extremely rare but can have severe consequences.

Transmission to Humans:

  • Direct Contact: Human infections usually occur through direct contact with infected birds, their bodily fluids, or contaminated surfaces.

  • Occupational Exposure: Individuals who work closely with infected birds or cattle, either in the poultry or dairy industries, may be at higher risk of exposure.

  • Limited Human-to-Human Transmission: Although rare, there have been a few documented instances of limited human-to-human transmission of HPAI strains. However, sustained human-to-human transmission has not been observed.

Impact on Human Health:

  • Severity: Human infection with HPAI strains can range from mild respiratory symptoms to severe illness, including respiratory distress syndrome, organ failure, and death.
  • Case Fatality Rate: The case fatality rate varies depending on the HPAI strain, with some strains having higher mortality rates than others.
  • Severity Factors: The severity of the illness may depend on several factors, including the individual's overall health, age, and any underlying medical condition.

Reporting and Testing:

  • Suspected cases of HPAI must be reported immediately to the USDA and state animal health officials.
  • Each state has specific guidelines for reporting, and veterinarians should contact their state veterinarian's office for guidance.
  • Polymerase chain reaction and agar gel immunodiffusion testing are available for HPAI detection in poultry.

By staying informed about HPAI outbreaks, implementing biosecurity measures, and promptly reporting suspected cases, veterinarians play a vital role in preventing and managing the spread of this highly pathogenic virus. Education and awareness among pet owners are key to reducing the risk of transmission and protecting both avian patients and public health.

 

References:

  1. Centers for Disease Control and Prevention (CDC):

     

  2. World Health Organization (WHO):

     

  3. Food and Agriculture Organization of the United Nations (FAO):

     

  4. Merck Manuals:

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  5. DVM 360: