#18,415
Over the past 3 weeks reports of outbreaks of HPAI H5N1 have taken off in British Columbia and the United States Pacific Northwest, with the arrival of a new genotype - D1.1 -carried by southbound migratory birds.
B.C. has reported more than 2 dozen poultry outbreaks, and Canada's first locally acquired human H5 infection is in a teenager - currently in critical condition - from the Fraser Valley region. While this patient's exposure remains unknown, an animal, bird, or environmental source is suspected.
Wildlife surveillance is generally limited to testing dead birds or mammals, and that requires both luck and good timing. Birds and mammals often die in remote regions and are never found or tested, and sometimes their carcasses are too badly decomposed to yield positive results.
As the following map illustrates, most of British Columbia can be described as remote, with the majority of its 5 million residents living in the southern third of the province.
British Columbia's Wildlife HPAI Dashboard provides us with a valuable snapshot of what has happened over the past 30 days with H5N1 in the region. Below is an example of just one of the ways to view the data; with a focus on environmental (sediment) detections, and detections in wild bird species.
The latest intelligence update summary follows, after which I'll return with more.
Wetland surveillance in B.C. appears to be limited to the Fraser river region - from roughly Chilliwack to its outflow into the Georgia Strait south of Vancouver - a distance of about 80 miles, all within 20 miles of the U.S. border.
HPAI continues to be found in wetland sediment throughout the Fraser Valley (note that only wetlands within the Fraser Valley are sampled). The most recent round of wetland sampling (which took place in late October) revealed the highest level of HPAI environmental contamination that has been seen this season. Additionally, HPAI detection in wild birds are increasing. The risk of infection in poultry is extremely high.
Note that all HPAI detections in wild birds are associated with the HPAI strain D1.1. This is the same strain is being detected in BC poultry and is a descendant of the A3 strain that was circulating in wild birds and poultry in the fall of 2023.
The detection of HPAI H5 in wetlands is significant because studies have shown the virus can remain viable for weeks, or even months in these environments, and that may facilitate the spread of the virus to other non-waterfowl species.
Water Research: Review of Influenza Virus in Water Environments Across Human, Poultry, and Wild Bird Habitats
Environmental Surveillance and Detection of Infectious HPAI Virus in Iowa Wetlands
Proc. Royal Society B: Influenza A Viruses Remain Viable For Months In Northern Wetlands - USGS
Although the spread of HPAI from bird-to-bird via contaminated surface water is the most obvious concern, we've seen ample evidence that semiaquatic mammals (otters, mink, muskrats, polecats, voles, etc.) are highly susceptible to avian flu infection (see Nature: Semiaquatic Mammals As Intermediate Hosts For Avian Influenza).
Other terrestrial mammals may drink from these waters as well. While most of these will be dead-end infections, every spillover to a mammalian host provides the virus with another opportunity to adapt and evolve.
It is a pretty good bet that similar HPAI ecosystems can be found all across North America, and around the globe. Places where HPAI H5 and other LPAI and HPAI viruses can hitch rides via migratory birds, swap genetic material via coinfections and reassortment, and experiment with mammalian adaptation.
The generation of a successful pandemic virus is admittedly a long shot, but nature has the advantage of time and an ever growing array of genetic building blocks with which to tinker.
Hopefully H5 will fall short, and never pose a pandemic threat. But nature's laboratory is open 24/7, making the next pandemic a matter of when, not if.
