Bulletin: First U.S. H5N1 detection in backyard swine on multi-species farm with poultry mortality

Sub-clade not specified initial announcements

State and federal animal health authorities today released coordinated press releases regarding the first diagnosis of H5N1 in backyard swine in Oregon in the United States:

Federal and State Veterinary Agencies Share Update on HPAI Detections in Oregon Backyard Farm, Including First H5N1 Detections in Swine | Animal and Plant Health Inspection Service

Detections of Highly Pathogenic Avian Influenza in Backyard Livestock – Oregon Department of Agriculture News

This is a follow-up to an official HPAI outbreak on the same Crook County Oregon farm posted last week on the USDA APHIS web site:

Confirmations of Highly Pathogenic Avian Influenza in Commercial and Backyard Flocks | Animal and Plant Health Inspection Service

The USDA press release states:

USDA’s National Veterinary Services Laboratories (NVSL) has conducted genomic sequencing of virus from the poultry infected on this farm, and that sequencing has not identified any changes to the H5N1 virus that would suggest to USDA and CDC that it is more transmissible to humans, indicating that the current risk to the public remains low. 

Local public health officials, Oregon Health Authority, Oregon State Veterinarian, Oregon Department of Agriculture, as well as the U.S. Department of Agriculture and U.S. Department of Health and Human Services are coordinating on this investigation and will provide additional updates as they become available.    

All detections of H5N1 include viral genome sequencing to provide additional information of interest to medical professionals and the research community to improve our understanding of the virus. Genetic sequencing for these samples is underway, though sequencing results may be inconclusive due to low viral levels in the samples.    

The above statements suggest that sequencing results from the poultry isolates are complete enough that USDA is comfortable in assuring CDC that there are “no changes to the virus indicating enhanced transmissibility. Therefore, both USDA and CDC are likely well aware of the subclade of this isolate, i.e. is it B3.13 (the dairy clade) or another perhaps migrant bird-delivered H5N1? The poultry isolate sub-clade is highly likely to be closely related to the swine isolate!

This is an initial finding in a new species (swine), and it’s crucial to know the lineage of the isolated strain. This information will undoubtedly be shared fairly soon, but it’s frustrating that such basic scientific information related to this novel finding has to be coaxed out of our “transparent” animal health agencies.

John