#18,348
While the jury remains out on whether an avian H5 influenza can spark a human pandemic (see Are Influenza Pandemic Viruses Members Of An Exclusive Club?), we continue to see an increasing number of worrisome spillovers into scores of mammalian species, including dairy cattle.
Human infections have risen over the past year to levels not seen in nearly a decade, and globally, we are dealing with a great many more H5Nx variants (subclades, subtypes & genotypes) than ever before.
Even if there is a species barrier that prevents an H5 virus from sparking a pandemic, twice in my lifetime (1957 & 1968) we've seen an avian virus reassort with human seasonal influenza to produce a pandemic strain (see Preprint: Intelligent Prediction & Biological Validation of the High Reassortment Potential of Avian H5N1 and Human H3N2 Influenza Viruses).
An H3 or an H1 virus with internal genes loaned from H5N1 could be both highly transmissible and virulent in humans. One need look no further than the infamous `Liverpool flu' of 1951 (see When Seasonal Influenza Goes Rogue) for evidence of the impact of a `mutated' seasonal flu virus.
While its been nearly a year since we first learned of H5N1's (genotype B3.13) spillover into cattle - which conservatively has spread to nearly 1,000 herds across 16 states - there are still a great many unknowns.
Complicating matters, a month ago, we learned that a second - potentially more dangerous genotype (D1.1) - has also infected herds in at least two states.
Despite these warning signs, the dairy industry and many agencies continue to treat H5N1 in cattle (and in poultry) as more of an economic problem than a public health threat. We've seen resistance on the part of farm workers, and their employers, to testing for the virus (in people & in livestock), and there remain a great many unknowns surrounding source, transmission, and threat of this virus in dairy cattle.
Yesterday the Journal Virology published an excellent mini-review by the The Risk Assessment Pipeline working group of the NIAID Centers of Excellence for Influenza Research and Response (CEIRR) Network, which looks at what we know - and what we don't know - about the pandemic risks posed by H5N1 in cattle.
This is a lengthy, and well-written review and I highly recommend that you read it in its entirety. While cattle-centric, it touches on other aspects, including spillover into cats, pigs, humans, and other species.
As sobering as all of this is, the long list of barriers to research should give us all pause.
I've only posted a miniscule portion of the review below, so follow the link, and plan to spend some time reading it. I'll have a brief postscript after the break.
Pandemic risk stemming from the bovine H5N1 outbreak: an account of the knowns and unknowns
Authors: Anice C. Lowen, Amy L. Baker, Andrew S. Bowman , Adolfo García-Sastre , Scott E. Hensley , Seema S. Lakdawala , Louise H. Moncla, Show All (16 Authors) , The Risk Assessment Pipeline working group of the NIAID Centers of Excellence for Influenza Research and Response (CEIRR) NetworkAuthors Info & Affiliations
https://doi.org/10.1128/jvi.00052-25
ABSTRACT
H5N1 subtype influenza A viruses represent a long-standing pandemic concern. Owing to their global occurrence in poultry, humans are routinely exposed to these viruses, and hundreds of human cases have been documented worldwide since 2003. The relevant viral lineages are not static, however, and have recently undergone a massive expansion of host range and geographic distribution. Within this expansion, the introduction of H5N1 viruses into dairy cattle in the United States has spawned a novel animal-human interface. In esponse, public health agencies have sought to evaluate the risk of an H5N1 pandemic stemming from the bovine outbreak. These assessments draw on evidence from the field and the laboratory to score a series of recognized risk factors. As such, their utility hinges on fundamental understanding of the processes that drive pandemic emergence and the availability of relevant data. Advancing this understanding and gathering data prior to and during an outbreak are primary missions of the NIAID Centers of Excellence for Influenza Research and Response (CEIRR) Network. To further these goals and highlight the need for an invigorated response across US agencies, here, we review gaps in understanding of the dairy cattle outbreak and identify constraints on efforts to close these gaps.
(SNIP)
(SNIP)
CONCLUSION
Meaningful assessment and effective mitigation of pandemic risk depend on a thorough understanding of the drivers of viral emergence and spread across animal and human populations. Both rapid outbreak-response and sustained research are needed to furnish the information required. At present, a deepening of the research response to the ongoing H5N1 panzootic will help to define the scope of the outbreak and the nature of human exposure. The knowledge gained will enable the design of biosecurity measures to diminish H5N1 circulation in animals, thereby reducing human exposure. Now and over the long term, research is needed to better define the factors that allow influenza pandemics to occur. While certain features are well-defined, uncertainty remains as to whether a given zoonotic threat can trigger a pandemic. Such research will enable more accurate assessment of risk, in turn allowing targeted preparation of antivirals, vaccines, and other interventions that can reduce the impact of an outbreak.
Thirty years ago anthropologist and researcher George Armelagos of Emory University posited that since the mid-1970s the world has entered into an age of newly emerging infectious diseases, re-emerging diseases and a rise in antimicrobial resistant pathogens (see The Third Epidemiological Transition (Revisited).
Emerging infectious diseases have become such an important public health threat that the CDC maintains as special division – NCEZID (National Center for Emerging and Zoonotic Infectious Diseases) – to deal with them, and in the 1990s the CDC established the EID Journal dedicated to research on emerging infectious diseases.
Recent studies suggest that the frequency, and impact, of pandemics are only expected to increase over the next few decades.
BMJ Global: Historical Trends Demonstrate a Pattern of Increasingly Frequent & Severe Zoonotic Spillover Events
PNAS Research: Intensity and Frequency of Extreme Novel Epidemics
And yet, at this critical juncture in history, we are dismantling our disease surveillance, investigative, and reporting systems (see Flying Blind In The Viral Storm). Many nations - including our own - have chosen to ignore the IHR 2005 regulations and stop (or severely limit) reporting to the WHO and WOAH on outbreaks (see From Here To Impunity).
While I can't tell you if H5Nx will spark the next pandemic, something will.
Probably a novel flu virus, but there are plenty of other contenders; coronaviruses, henipaviruses, bunyaviruses . . . or maybe something out of left field.
Abandoning basic science, research, and disease mitigation tools - like vaccines and face masks - may help fulfill some populist agenda - or produce some temporary economic gain - but it will ultimately result in needless deaths and suffering.
But at least our leaders can honestly say when the next pandemic does arrive:
They never saw it coming . . .