Although we discussed it at some length yesterday (see H5N1 Detected In B.C. Backyard Flock), we now have the OIE Notification which includes some additional epidemiological and sequencing information that indicates this H5N1 is very similar to the H5N1 virus detected last month in a green-winged teal in Whatcom County, Washington (see OIE: New Reassortant HPAI H5N1 In North America)
Source of the outbreak(s) or origin of infection
- Unknown or inconclusive
- Contact with wild species
This new outbreak was detected in a backyard poultry flock in the Avian Influenza Primary Control Zone (PCZ) in the province of British Columbia (BC), in the same area as the previous outbreaks of HPAI H5N2 reported in December 2014. All susceptible animals on site were humanely destroyed. The National Centre for Foreign Animal Disease (CFIA - Winnipeg) reported NAI H5 RRT-PCR positive results on 4 February 2015 and partial sequencing of H5 and N1 segments on 5 February.
The virus involved is a HPAI H5N1 virus with the H5 gene segment derived from the Eurasian lineage, and N1 derived from North American lineage based on partial sequence. The H5 gene segment is very similar to the reassortant H5N2 in BC and the H5 in the H5N1 reassortant virus detected in a wild green-winged teal just south of the border in Washington State, USA. In addition, the N1 gene segment is very similar to North American wild bird viruses and nearly identical, over the very small fragment sequenced this far, to the N1 in the H5N1 virus detected in a green-winged teal mentioned above.
Based on the limited partial sequence of the H5 and N1 gene segments obtained this far, it appears very likely that this is the same or a very similar virus to the recent reassortant H5N1 virus in Washington State but more sequencing will be needed to make a final conclusion. This virus has NOT been reported in any commercial poultry flock in Canada. It is important to note this HPAI H5N1 virus is different from the strain circulating in Asia. It is a reassortant virus with the N1 from a North American wild bird virus. The Canadian Food Inspection Agency (CFIA) continues to monitor the situation and implement strict movement restrictions in the PCZ. Ongoing surveillance is in place in all of Canada. All provinces, with the exception of the PCZ in British Columbia, remain free of Notifiable Avian Influenza in poultry.
As I pointed out yesterday, this is a new reassortment, not the same H5N1 that has plagued China, Southeast Asia, and the Middle East over the past decade.
While carrying the same HA/NA designations as its more infamous Asian cousin - this subtype is comprised of gene segments from the Eurasian (EA) H5N8 virus, along with genetic contributions from North American (AM) avian viruses.
Our knowledge of how this new reassortant virus will behave in poultry, and in humans, is very limited at this time. Other reassortants carrying this H5 gene segment (H5N8, H5N2) have not yet been shown to pose a health risk to humans.
Whether that holds true with this virus remains to be seen.
For now the CDC is taking a cautious approach to all of of these recently arrived HPAI viruses, and has issued guidance for the testing, and prophylactic treatment of those exposed.