Avian Influenza Virus — A Global Threat to Poultry Health

Virus Classification

Avian influenza viruses are categorized based on two surface proteins -

Hemagglutinin (H): 18 known subtypes (H1–H18)

Neuraminidase (N): 11 known subtypes (N1–N11)

Combinations such as H5N1, H5N8, and H7N9 have caused major outbreaks in birds and occasionally infected humans.

Transmission

AIV spreads mainly through:

• Direct contact between infected and healthy birds
• Contaminated feed, water, or equipment
• Wild migratory birds, which act as natural reservoirs

The virus can survive for long periods in the environment, especially in cool and moist conditions, allowing rapid transmission among flocks.

Pathogenicity Levels

Avian influenza viruses are classified into two major categories:

• Low Pathogenic Avian Influenza (LPAI) – often causes mild or no symptoms.
• Highly Pathogenic Avian Influenza (HPAI) – leads to severe illness and high mortality rates, particularly in poultry farms.

HPAI strains such as H5N1 and H5N8 have led to devastating outbreaks globally, causing significant economic losses due to culling and trade restrictions.

Clinical Signs in Birds

Symptoms vary depending on the strain and bird species but may include:

• Sudden death without signs
• Drop in egg production
• Swelling around the head and neck
• Respiratory distress, coughing, or sneezing
• Cyanosis (bluish discoloration) of comb and wattles

Global Impact

Avian influenza outbreaks have been reported worldwide, affecting poultry production, trade, and food security. Wild birds play a key role in spreading new viral strains across continents during migration seasons.
Recent years have seen recurrent H5N1 and H5N8 epidemics in Asia, Europe, and North America, emphasizing the need for continuous surveillance and biosecurity measures.

Prevention and Control

Effective control relies on:

• Strict biosecurity to prevent virus entry and spread
• Surveillance and early detection in both domestic and wild bird populations (recommend using J&G AIV Rapid Test to support timely disease monitoring and management)
• Culling and disinfection during outbreaks
• Vaccination in high-risk regions, where applicable

Avian influenza remains a major challenge to the global poultry industry, requiring constant vigilance, international cooperation, and scientific advancement to mitigate its impact.