Antibodies to Influenza A(H5N1) Virus in Hunting Dogs Retrieving Wild Fowl, Washington, USA Antibodies to H5 and N1 subtypes of influenza A virus were detected in 4 of 194 hunting dogs in Washington, USA, that had hunted or trained with wild birds. Historical data from dog owners indicated that seropositive dogs had high exposure to waterfowl. Since 1996, H5 highly pathogenic influenza A viruses (HPIAV) have caused a global outbreak. In 2020, a sub-clade 2.3.4.4b HPIAV H5N1 emerged and spread to multiple continents, causing significant deaths in poultry and wild birds. Increased detection in mammals has raised concerns about the virus adapting to mammal hosts. Despite the global outbreak of HPIAV H5N1, infections in dogs have been rare. In 2004, a fatal canine infection in Thailand was reported, and in 2023, a fatal infection in Ontario, Canada, was identified. Experiments showed that beagles were susceptible to HPIAV H5N1, but clinical outcomes varied. Existing data suggest dogs are susceptible to HPIAV H5N1, but clinical outcomes vary. However, infection appears to be restricted to dogs with high virus exposure. To investigate further, antibodies to influenza A(H5N1) virus were tested in bird hunting dogs, a high-risk group. Dog owners provided information about their dogs' retrieving activities, CIV vaccination status, and clinical history. Blood samples were collected from 194 dogs in Washington, USA, between March and June 2023. Serum samples were tested for antibodies to influenza A virus using various assays. Antibodies to IAV were detected in 9.3% of dogs. Of the 18 bELISA-positive samples, 14 were seropositive for CIV H3N2 and 13 for CIV H3N8. Four dogs were seropositive for H5 and N1 antibodies. Three of these dogs had not been vaccinated for CIV and were negative for H3N2 and H3N8 antibodies. All 11 bELISA-negative samples tested negative for H5 antibodies, but three were seropositive for N1. The study found that antibodies to H5 and N1 were only detected in hunting dogs with high levels of bird hunting and waterfowl retrieval. Although transmission from waterfowl to dogs can occur, low seroprevalence, lack of reported disease in seropositive dogs, and lack of evidence for dog-to-dog transmission suggest that the subclade 2.3.4.4b HPIAV H5N1 strains were poorly adapted to dogs. Effective risk communication with huntingAntibodies to Influenza A(H5N1) Virus in Hunting Dogs Retrieving Wild Fowl, Washington, USA Antibodies to H5 and N1 subtypes of influenza A virus were detected in 4 of 194 hunting dogs in Washington, USA, that had hunted or trained with wild birds. Historical data from dog owners indicated that seropositive dogs had high exposure to waterfowl. Since 1996, H5 highly pathogenic influenza A viruses (HPIAV) have caused a global outbreak. In 2020, a sub-clade 2.3.4.4b HPIAV H5N1 emerged and spread to multiple continents, causing significant deaths in poultry and wild birds. Increased detection in mammals has raised concerns about the virus adapting to mammal hosts. Despite the global outbreak of HPIAV H5N1, infections in dogs have been rare. In 2004, a fatal canine infection in Thailand was reported, and in 2023, a fatal infection in Ontario, Canada, was identified. Experiments showed that beagles were susceptible to HPIAV H5N1, but clinical outcomes varied. Existing data suggest dogs are susceptible to HPIAV H5N1, but clinical outcomes vary. However, infection appears to be restricted to dogs with high virus exposure. To investigate further, antibodies to influenza A(H5N1) virus were tested in bird hunting dogs, a high-risk group. Dog owners provided information about their dogs' retrieving activities, CIV vaccination status, and clinical history. Blood samples were collected from 194 dogs in Washington, USA, between March and June 2023. Serum samples were tested for antibodies to influenza A virus using various assays. Antibodies to IAV were detected in 9.3% of dogs. Of the 18 bELISA-positive samples, 14 were seropositive for CIV H3N2 and 13 for CIV H3N8. Four dogs were seropositive for H5 and N1 antibodies. Three of these dogs had not been vaccinated for CIV and were negative for H3N2 and H3N8 antibodies. All 11 bELISA-negative samples tested negative for H5 antibodies, but three were seropositive for N1. The study found that antibodies to H5 and N1 were only detected in hunting dogs with high levels of bird hunting and waterfowl retrieval. Although transmission from waterfowl to dogs can occur, low seroprevalence, lack of reported disease in seropositive dogs, and lack of evidence for dog-to-dog transmission suggest that the subclade 2.3.4.4b HPIAV H5N1 strains were poorly adapted to dogs. Effective risk communication with hunting