Avian influenza, or bird flu, refers to infections in birds caused by influenza viruses. These viruses circulate among wild aquatic birds worldwide and can infect domestic poultry and other bird and animal species. Bird flu is a recurring concern in Japan, frequently impacting its poultry industry and wild bird populations.
Bird Flu in Japan: A Closer Look
Highly pathogenic avian influenza (HPAI) is the primary concern in Japan due to its ability to cause severe disease and high mortality in poultry. Japan’s location along major migratory bird routes makes it susceptible to outbreaks. Wild aquatic birds, like ducks, carry these viruses, introducing them to domestic poultry farms during seasonal migrations from breeding grounds, often in Siberia, to wintering sites.
Dense poultry farming in Japan allows rapid virus spread. Outbreaks frequently occur from late autumn to early spring, aligning with wild bird migration. Historically, H5N1 has been a detected strain, with occurrences reported as early as 2004, marking Japan’s first HPAI outbreak in 79 years. More recently, H5N8 and H5N2 subtypes have also been identified in poultry and wild bird populations.
The 2022-2023 season marked Japan’s largest HPAI epidemic, with 84 outbreaks across 26 prefectures and approximately 17.71 million birds culled. This season also saw the earliest detection of HPAI viruses in wild birds, a month earlier than in previous years, suggesting a shift in detection patterns. Multiple genetic groups of H5N1 and H5N2 subtypes entered the country, contributing to widespread outbreaks.
Consequences and Human Health Concerns
Bird flu outbreaks in Japan have substantial consequences for the poultry industry. Mass culling of infected and exposed birds is a standard measure to contain spread, leading to significant economic losses for farmers. In January 2025 alone, over 5 million birds were culled, bringing the season’s total to 8.1 million. These large-scale culls can disrupt the supply chain for poultry meat and eggs, affecting market prices and availability.
The risk of bird flu transmission from birds to humans is generally low, and human-to-human transmission is rare. However, zoonotic spillover can occur with close, prolonged, or unprotected contact with infected birds or contaminated environments. Individuals like poultry farm workers, veterinarians, or those involved in culling operations may face a higher exposure risk. If human infection occurs, symptoms can range from mild conjunctivitis to severe respiratory illness, including pneumonia. Public health advice emphasizes avoiding contact with sick or dead birds and ensuring poultry products are thoroughly cooked to eliminate any viral presence.
Japan’s Measures to Combat Bird Flu
The Japanese government and poultry industry implement measures to combat bird flu. Surveillance programs monitor wild bird populations and domestic poultry farms, involving regular testing and observation for early virus detection. When outbreaks occur, strict biosecurity protocols are enforced on affected farms to prevent further spread.
Culling is initiated for infected flocks and those in close proximity to outbreaks to contain the virus. In January 2025, approximately 1.44 million birds were destroyed across seven farms in Aichi and Chiba prefectures following confirmed cases. Movement restrictions are imposed on poultry and related products within designated zones around affected farms.
Disinfection efforts are carried out to eliminate the virus from contaminated premises. The government provides compensation schemes to affected farmers. Public awareness campaigns and guidelines are issued to educate the public on precautions and reporting procedures for sick or dead birds.