Samira Mubareka is an infectious diseases physician and virologist at Sunnybrook Research Institute and University of Toronto, and Chair of the RSC Working Group on One Health
Shayan Sharif is a Professor and Associate Dean, Research and Graduate Studies at the Ontario Veterinary College
Over the past year there has been an unprecedented level of highly pathogenic avian influenza (HPAI) activity among wild birds and domestic poultry in North America. Since HPAI first appeared in Newfoundland in late 2021, there have been over 140 domestic poultry outbreaks across nine provinces, affecting farmed and backyard chickens, ducks, and turkeys, resulting in the depopulation of millions of animals in Canada alone. Even though there is no direct threat to human health through the food supply, ongoing HPAI activity has driven the cost of poultry products up, compounding rising food prices and global food insecurity catalyzed by the war in Ukraine, the COVID-19 pandemic, and high rates of inflation.
The impact on wildlife health has also been significant, and although the precise number of wild birds affected is unknown, the Canadian Food Inspection Agency, Environment and Climate Change Canada, and the Canadian Wildlife Health Cooperative have reported cases across 13 provinces and territories, involving a wide range of species, including (but not limited to) waterfowl, seabirds, and raptors such as eagles, hawks, and owls. Alarmingly, massive die-offs of gulls, gannets, and other birds have been observed in several provinces. Yet, limited public attention has been paid to a pathogen that simultaneously imperils domestic animal, wildlife, and human health, and remains the leading next pandemic threat.
What exactly is HPAI?
HPAI differs from seasonal, human influenza in several ways. At the molecular level, HPAI and other avian (bird) influenza viruses preferentially bind a different host cell receptor than mammalian (e.g., human) influenza viruses. Thus, they tend to infect birds, but can acquire mutations that enable infection and replication in other species, including humans.
Even without these mutations, avian influenza viruses can infect humans, partly because we don’t have pre-existing immunity to avian influenza viruses. Human infections can potentially lead to severe disease and death. This is why avian influenza remains a leading public health risk; if it acquires the ability to transmit among humans, it may cause another large-scale global pandemic.
Because the main reservoir for HPAI and other avian influenza viruses is wild waterfowl, global spread generally occurs along migratory bird flyways, spreading the virus to other wild birds as well as domestic poultry.
There have also been reports of multiple spillover events into wild mammals, including a bear, foxes and seals in Canada. These highly unusual events are of significant concern since they signal the possibility of viral adaptation to mammalian hosts, and further threatens wildlife health. Also, we anticipate resurgent seasonal human influenza activity this fall and winter, raising the possibility of further viral reassortment (exchange of viral genetic material) and emergence of a novel influenza virus in humans.
What is driving this global surge in HPAI?
Regions of Europe and Africa have also been experiencing extremely high levels of HPAI activity. The complex interplay between host species, migration, farming practices, ecosystems, climate, and viral biology suggests that it may be multifactorial. As an example, climate change has had an impact on the ecology of migratory birds, which are reservoirs of HPAI, thus potentially changing the population dynamics of virus transmission and increasing the possibility of new variant emergence. The virus itself is also a major contributor; it is changing and gaining in genetic diversity, creating new opportunities for viral adaptation.
It is critical to understand the relative contributions of potential drivers at both molecular and population scales to mitigate further spread and spillover, and ideally, prevent the next pandemic. Robust monitoring and surveillance of wildlife and domestic animals are essential to predicting, detecting, and responding to emerging pathogens, and are the cornerstones of sound pandemic preparedness and emerging pathogens programs from both regional and global perspectives.
Although data collection and sharing are essential, it is of limited value if it is not tied to effective action. This may include further data acquisition, program implementation, and communication, policy, and decision-making to reduce exposure and develop or implement non-pharmaceutical and pharmaceutical interventions.
For HPAI, immediate actions have been taken to control individual outbreaks, but there is yet to be a coordinated, cross-sectoral (academic, public, and animal health and commercial sectors), multi-agency and multi-institutional approach. Despite laudable efforts by individual programs, agencies, and institutions, there is no overarching mechanism by which these efforts may be coordinated and amplified. There is also an established disparity in resources for animal versus human health, with longstanding and substantial underfunding of animal health research and program implementation.
Addressing critical challenges at the nexus of ecosystems, humans, and other animal species requires an approach that considers the inter-dependencies involved. The One Health approach is multi-disciplinary and encompasses relevant key areas where humans intersect with other animals and the environment, with the potential to bridge gaps and achieve shared goals for public health and global security.
Even if the merits of the One Health approach are gaining appreciation in Canada, we have yet to nurture the societal and institutional changes necessary to effectively implement this approach. It is important for civil society to broadly recognize that land management, conservation, food production, human and other animal mobility, climate change, socioeconomics, and geopolitics are closely tied to the biology, ecology, and epidemiology of human and other animal pathogens, with cyclical impacts on society, human and other animal populations, and planetary health. Now is the time to implement key programs that address all these factors to build resilience and attenuate the impacts of current and future emerging pathogen outbreaks and pandemics. There have not been any human cases of HPAI infection in Canada yet, though they have been reported in other jurisdictions— waiting for more human cases to emerge will cost opportunities to intervene effectively. This is a known threat, and complacency at this stage is unconscionable.
What now?
As HPAI continues to proliferate among wild birds and spillover into a growing list of mammals, there is a pressing need for immediate and coordinated collaborative action involving public, academic, and private sectors to understand the drivers of viral transmission and enable additional means to mitigate spread. It is also critical to understand the risks to human and other animal health and pandemic triggers. Often, we recognized ‘the perfect storm’ for rare but highly impactful events after they happen. HPAI has already had a profound impact on wildlife, with potential knock-on effects on ecosystem health. It is difficult to imagine a more critical time to implement the Pan Canadian Approach to Wildlife Health, which outlines and supports the protection of wildlife health and the value it brings to Canadians and the ecosystems we share. This is urgently needed not only to address the ongoing threat of HPAI, but the many other hazards that threaten wildlife populations, including land use and climate change. A broader, Canadian One Health Action Plan is also warranted, with purposeful means to address the ongoing threat to domestic poultry, wildlife and human health posed by HPAI in the near term, and to address other emerging pathogens at regional, national, and global scales in the longer term. Reducing risk is contingent on restoring balance by directly addressing the drivers of pathogen spillover, amplification, spread and impact. One Health provides us with the approach - it is now up to us to use it.