Current HPAI Outbreak Status In India   

Prof.Dr, R.N.Sreenivas Gowda

Avian influenza (AI) in poultry is a highly contagious viral infection (primarily H5 and H7 subtypes) that can cause low (LPAI) or high (HPAI) pathogenicity, with HPAI leading to massive systemic illness and mortality, especially in chickens and turkeys. It spreads via wild bird contact, causing severe economic damage, and is zoonotic, requiring strict biosecurity to protect flocks.

India is currently managing multiple H5N1 outbreaks across several states, with seasonal activity continuing beyond the typical January-March peak.

 Latest Outbreaks (2025–2026)

India reported 41 outbreaks across 10 states in 2025. Recent activity includes:

• Karnataka (April 2026):An outbreak of H5N1 was confirmed at a government poultry training centre in Hesaraghatta, Bengaluru. Over 7,400 birds were culled. Intensive 10-day surveillance of 28,000 people in the area confirmed no human infections.
• Bihar (April 2026):H5N1 was confirmed at a poultry farm in Bhagalpur, leading to culling and sanitisation measures. Widespread transmission reported in six districts, including crows and commercial poultry in Patna as of March 2026
• Tamil Nadu (February 2026):A high alert was issued in Chennai after the death of over 1,500 crows from the H5N1 virus.
• Kerala (December 2025):11 outbreaks of H5N1 occurred in the Alappuzha and Kottayam districts, leading to the death or culling of over 84,000 birds
• Other Regions: Cases have also been detected recently in
• Chhattisgarh, Jharkhand and Telangana.

Why outbreaks of avian flu is common in summer in India?

 While avian flu outbreaks in India are historically most common from post-monsoon through winter (October to March), occurrences in summer (April to June) have become a growing concern due to environmental and biological stressors.

Factors Contributing to Summer Outbreaks

• Summer Heat Stress & Immunosuppression: Intense summer heat acts as a significant environmental stressor for poultry. Chronic heat stress has been shown to:
• Suppress innate immunity: High temperatures can reduce local respiratory immunity and weaken the maturation of immune cells, making birds more susceptible to pathogens.
• Increase viral load: In experimental models, heat-stressed subjects showed higher viral loads and mortality rates when infected with H5N1 compared to those in temperate conditions.
• Cause vaccine failure: Heat stress in summer is a known contributor to vaccine failures and overall immunodeficiency in poultry.
• Environmental Persistence & Humidity: While the virus typically survives longer in cold, wet conditions, high humidity during warm periods (pre-monsoon/summer) can also improve virus survival compared to warm, dry air.
• Changes in Migratory Patterns: Climate change is altering the paths and timing of migratory birds, which are natural reservoirs for the virus. This can lead to the “import” of the virus outside of traditional peak winter windows.
• Poultry Management Issues: High stocking densities in poultry sheds can exacerbate summer heat and humidity, facilitating rapid spread if the virus is introduced.

General Trends in India

• Peak Season: Most outbreaks still peak in January.
• Summer Occurrences: Outbreaks recorded in 2024 and 2025 have continued into July, with cases reported in states like Maharashtra, Jharkhand, and Chhattisgarhduring these warmer months.
• Risk Variables: Significant predictors for summer risk include air temperature, specific humidity, and potential evapotranspiration (PET).

Clinical Signs Supporting Diagnosis
Diagnosis is initiated when flock managers observe specific symptoms:

• Sudden, high mortality:A large percentage of the flock dies rapidly.
• Respiratory issues:Coughing, sneezing, and nasal discharge.
• Drop in production:Significant decrease in egg production or soft/misshapen eggs.
• Physical signs:Purple discoloration of wattles/comb, edema of the head, and nervous signs (tremors, twisted necks).
• Behavioral changes:Lethargy, reduced water/food consumption

 Diagnosis

Diagnosis of bird flu (Avian Influenza – AI) in poultry involves clinical observation of symptoms like sudden death, high mortality, and respiratory distress, followed by laboratory confirmation. The “gold standard” is detection of viral RNA via real-time reverse transcription-polymerase chain reaction (rRT-PCR) from swabs. Other methods include virus isolation and ELISA for antibodies.

ACIA (Antigen-Capturing Immunoassays): Portable, “pen-side” tests that provide results in about 15 minutes. They are useful for screening sick or dead birds but have lower sensitivity than PCR.

RDDLS: Bangalore,Jandhar. Pune, Kolkata and IVRI,Izatnagar labs test the material and High security lab ,Bhopal will confirm the disease.

Control of Bird Flu through Vaccines?

In India, the use of vaccines to control bird flu is currently restricted based on the severity of the virus strain. The government distinguishes between Low Pathogenic (LPAI) and Highly Pathogenic (HPAI) strains in its vaccination policy.

 Current Vaccination Policy

• Permitted (H9N2 Strain): The government has officially permitted the use of an indigenous vaccine for Low Pathogenic Avian Influenza (LPAI H9N2). This vaccine, developed by ICAR-NIHSAD in Bhopal, is commercially available to help prevent the sub-clinical or mild disease that causes significant economic losses.
• Not Permitted (H5N1 Strain): Preventive vaccination for Highly Pathogenic Avian Influenza (HPAI H5N1)is currently not allowed in India. The country continues to follow a strict “detect and cull” strategy for these severe outbreaks to ensure the complete eradication of the virus.

Why HPAI (H5N1) Vaccines Are Restricted

India’s National Action Plan limits H5N1 vaccination for several strategic reasons:

• Silent Spread: Vaccinated birds may still carry and shed the virus without showing symptoms, making it harder to detect and contain new outbreaks.
• Viral Mutation: Experts worry that long-term vaccination could lead to the emergence of vaccine-resistant strainsor cause the virus to become endemic in the poultry population.
• Incomplete Immunity: Current HPAI vaccines often only reduce virus shedding rather than providing “sterile immunity” (complete protection from infection).
• Trade Restrictions: Implementing wide-scale HPAI vaccination can negatively impact India’s status with the World Organisation for Animal Health (WOAH), affecting the export of poultry products.

 Decision to vaccinate chickens in India

In India, the decision to vaccinate chickens depends on whether the threat is from Low Pathogenic (LPAI) or Highly Pathogenic (HPAI) bird flu strains. Official policy currently supports vaccination only for the milder LPAI H9N2 strain, while maintaining a strict “detect and cull” strategy for HPAI H5N1.

Quick Comparison: To Vaccinate or Not?

Why India Restricted H5N1 (HPAI) Vaccination

Although vaccines can reduce mortality by 78% to 97% in controlled trials, the Department of Animal Husbandry & Dairying (DAHD) continues to restrict H5N1 vaccination due to:

• “Silent Spread”: Vaccinated birds may not show symptoms but can still shed the virus, making it invisible to surveillance.
• Viral Evolution: Continuous vaccination can drive the virus to mutate into new “vaccine-resistant” strains.
• Export Restrictions: Many international trade partners refuse poultry from countries that vaccinate for HPAI, as they cannot distinguish between vaccinated and naturally infected birds.
• Lack of Sterile Immunity: Current HPAI vaccines often only reduce shedding rather than providing complete protection from infection.

Arguments for Vaccination

The Indian poultry industry has recently urged the government to reconsider this stance due to recurring losses.

• Sustainable Control: Mass culling is increasingly viewed as unsustainable and expensive for farmers.
• Advanced Technologies: New “DIVA” (Differentiating Infected from Vaccinated Animals) vaccines and recombinant vector vaccines (like ICAR-NIHSAD’s indigenous candidate) may soon allow for vaccination without losing the ability to track the virus.

Current Recommendation for Farmers (2025–2026)

1. H9N2 Vaccination: If your farm is at risk for mild production drops, use the commercially available H9N2 vaccinedeveloped by ICAR-NIHSAD.
2. Biosecurity First: For H5N1 protection, focus on stricter biosecurity—controlling farm access, sanitizing equipment, and preventing contact with wild birds.
3. Mandatory Registration: Ensure your farm is registered with your state’s Animal Husbandry Department to be eligible for government compensation schemesin case culling is ordered.

Human Cases in India

Human infections are rare and typically sporadic:

• Andhra Pradesh (March 2025):A fatal H5N1 case was reported in a 2-year-old girl in Mangalagiri, suspected to be from consuming raw chicken.
• West Bengal (May 2024):A 4-year-old child was infected with the H9N2 strain and fully recovered after treatment.
• Haryana (July 2021):India’s first confirmed fatal H5N1 human case was an 11-year-old boy.

Prevention and Food Safety

Health authorities emphasize that properly cooked poultry and eggs are safe to eat, as the virus is heat-sensitive.

• Cooking:Ensure chicken and eggs reach an internal temperature of at least 74°C (165°F); meat should no longer be pink.
• Avoid Raw Products:Do not consume raw or undercooked meat, half-boiled eggs, or unpasteurized (raw) milk.
• Hygiene:Wash hands with soap and water after handling raw poultry, and disinfect all kitchen surfaces.
• Reporting:Report any sudden or unusual bird deaths (including wild birds like crows) to the local Animal Husbandry Department.

Symptoms to Watch For

If you have been in contact with birds and experience these symptoms, seek medical attention immediately:

• High fever (above 38°C)
• Persistent cough and sore throat
• Difficulty breathing or chest pain
• Red, watery, or swollen eyes (conjunctivitis)
• Severe muscle aches and fatigue

Biosecurity

The Indian government enforces a strict three-pronged biosecurity strategy—Conceptual, Structural, and Operational—under the National Action Plan (2021) to control bird flu. These practices are designed to prevent the introduction of pathogens and are mandatory for all registered poultry farms.

Conclusion

Bird flu (Avian Influenza) in chickens is a highly contagious viral disease caused by influenza type A viruses, ranging from low pathogenicity to highly pathogenic (HPAI) strains that cause rapid, high-mortality outbreaks. Diagnosis relies on laboratory testing (PCR, virus isolation) following clinical signs like respiratory distress and swollen heads. Control involves strict biosecurity, culling infected flocks, movement restrictions, and potential vaccination.