Avian Influenza

Maharashtra reported India’s first H5N1 avian influenza case in animals, marking a significant wildlife health concern.

Recent Impact on Animals

• Mortality: Three tigers and one leopard succumbed to H5N1 at the Balasaheb Thackeray Gorewada Zoo, Nagpur.
• Transmission: Animals were infected after being rescued from Chandrapur, highlighting disease spread in captive wildlife.
• First Instance in India: This is the first documented case of H5N1 causing fatalities among captive wildlife in the country.

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About Avian Influenza (H5N1)

• H5N1 Overview
  • H5N1 is a type of influenza virus causing severe respiratory disease in birds.
  • It is a subtype of the influenza A virus, classified based on surface protein properties.
• Classification of Influenza A Viruses
  • Influenza A viruses are categorized by hemagglutinin (H) and neuraminidase (N) proteins.
  • There are 18 hemagglutinin (H1-H18) and 11 neuraminidase (N1-N11) subtypes.

Emergence and Evolution of H5N1 Bird Flu

• 1996-1997: H5N1 was first identified in domestic waterfowl in Southern China.
  • Named A/goose/Guangdong/1/1996, it caused outbreaks in China and Hong Kong with 18 human cases (6 deaths).
• 2003-2005: H5N1 re-emerged, causing widespread poultry outbreaks across Asia, spreading to Africa, the Middle East, and Europe via wild birds.
• 2014-2016: Gene-swapping led to H5N6 and H5N8 subtypes, diversifying hemagglutinin (HA) into clade 2.3.4.4.
• 2018-2020: Clade 2.3.4.4b becomes predominant globally, replacing original H5N1 viruses.
• 2021-2023: Clade 2.3.4.4b H5N1 detected in wild birds in Canada and the U.S., causing outbreaks in poultry and sporadic infections in humans and mammals.
  • Example: A(H1N1), which causes swine flu.

Transmission of Avian Influenza

• Bird-to-Bird: Transmitted via direct contact, saliva, nasal secretions, feces, or contaminated surfaces.
• Bird-to-Human: Rare but occurs through close contact with infected birds or contaminated environments.
• Human-to-Human: As per research Published in Science Journal The H5N1 avian influenza virus is one mutation away from becoming infectious to humans, enabling it to spread from one person to another.
• Mortality and Pandemic Potential
  • Mortality rates can reach up to 60%.
  • Avian influenza is not currently on the WHO’s priority list of pathogens with pandemic potential.

Symptoms of Avian Influenza

• The symptoms of H5N1 infection may include fever (often high fever, > 38°C) and malaise, cough, sore throat and muscle aches.
• Other early symptoms may include conjunctivitis and other non-respiratory symptoms.
• The infection may progress quickly to severe respiratory illness and neurologic changes (altered mental status or seizures).
• H5N1 virus has also been detected in samples collected from people without symptoms who had exposure to infected animals or their environments.

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Preventive Measures and Recommendations

• Zoo and Wildlife Protocols
  • Biosecurity measures to prevent bird access to other animals using nets and covers.
  • Disinfection of footwear and equipment and maintenance of hygiene.
  • Avoid feeding carnivores raw poultry or meat from unverified sources.
  • Regular health monitoring of animals for unusual behavior or symptoms.
• State and Facility-Level Actions
  • Temporary shutdown of affected facilities for public access.
  • Isolation of infected or symptomatic animals.
  • Enhanced surveillance and early detection measures across zoos and rescue centers.
• One-Health Approach: Integration of efforts across human health, animal health, and wildlife sectors to address the risks of avian influenza comprehensively.